Details of a Researcher - Ishigure, Takaaki

Papers - Ishigure, Takaaki

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Temperature dependence of the coupling loss between polymer optical waveguides and SMF for co-packaging

Kinoshita R., Ishigure T.

Optics Express 33 ( 1 ) 1271 - 1286 2025.01

We theoretically calculate the coupling loss between single-mode fibers (SMFs) and polymer optical waveguides with different refractive index profiles. Temperature resistance is one of the concerns when integrating polymer optical waveguides near the electronics and photonics chips where they are highly likely to dissipate heat. Hence, the calculation focuses on the core size variations due to changes in operating temperature. The calculated results show that the refractive index variation with respect to temperature has a greater impact on coupling loss compared to the temperature-dependent core size variation. Then, polymer optical waveguides are experimentally fabricated and characterized. The temperature dependence of the output light intensity distribution from the fabricated waveguides is observed, as it is estimated by the theoretical calculation. In addition, it is also found that graded-index cores in polymer waveguides demonstrate slightly higher temperature stability in connection with SMF than their step-index counterparts. Such a low coupling loss with SMF could be maintained even in an environment at 100 °C, making polymer optical waveguides promising for the application of co-packaged optics.

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Optimum core structural design of the polymer optical waveguides as edge couplers for co-packaging

Kinoshita R., Ishigure T.

Optics Express 32 ( 14 ) 24415 - 24431 2024.07

We simulate the optical properties of polymer optical waveguides with different refractive index profiles in their cores as coupling components (edge couplers) between single-mode fiber and SiOx waveguides. In this paper, we focus on the single-mode operation of graded-index (GI) core polymer waveguides, for which we previously demonstrated low propagation loss under multimode operation. We design the optimum core structure (size and index contrast) for different refractive index profiles, and then demonstrate the unique optical properties of GI waveguides contributing to the low optical loss compared to the step-index counterparts, in particular, mode field diameter variation and taper angle tolerance.

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Polarization manipulation on step-index composite polymer beam splitters for photonics circuitry

Afsary N., Tasnim F., Rasel M.O.F., Ishigure T.

Heliyon 10 ( 3 ) 2024.02

ISSN 24058440

This paper presents composite beam splitters realized with polymer materials for developing photonic integrated circuits. We used organic-inorganic hybrid polymer materials to form this composite beam splitter realized with step-index (SI) core profiles. We used the alternating direction implicit technique of the Rsoft CAD BeamPROP solver to design and analyze these beam splitters. We successfully examined and manipulated the beam splitter's polarization dependency to obtain a 99% output efficiency with a 50:50 splitting ratio. The SI beam splitter exhibits an excess loss of 0.014 dB. When we apply polarized light in this beam splitter, the excess loss increases to 2 dB, and this loss gradually decreases as the angle of incident light increases. The excess loss reduces to 0.05 dB at the 31-degree angles of the incident polarized light. We also investigated the crosstalk of this beam splitter by varying the wavelength, and it is evident that the lowest crosstalk is −19.77 dB at the polarized angle of 31°.

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Thermally reliable compact electro-optic modulators with a low half-wave voltage

Afsary N., Alam M.K., Rasel M.O.F., Ishigure T.

Optics Continuum 3 ( 6 ) 1012 - 1024 2024

Recent advancements in thin-film lithium niobate have led to the development of high-performance integrated electro-optic modulators, which are crucial for modern optical communication systems. These modulators offer tighter mode confinement, a smaller physical footprint, and reduced modulating voltages. This study presents a Mach-Zehnder modulator (MZM) on a silicon nitride-loaded lithium niobate platform using a few-mode waveguide structure. By harnessing the exceptional thermo-optic and electro-optic effects of LiNbO3, we design and simulate this modulator employing multilayer structures with the BeamPROP solver. The modulator has a length of 3.94 mm, a Vπ value of 0.96 V, and a transition temperature (Tg) of 80 °C at 1.55 µm. This proposed modulator exhibits a crosstalk of approximately-42 dB, an extinction ratio of approximately 24 dB, and a maximum transmission of-28 dB for the first-order phase shift. These findings demonstrate the significant potential of this modulator for deployment in high-speed optical communication systems, where maintaining thermal stability and optimizing energy efficiency are paramount.

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Structural Investigation of Microchannel and Optical Waveguide Co-integrated Sensor Devices

Ichizuka T., Ishigure T.

13th IEEE CPMT Symposium Japan: Innovation of Packaging Technology for Advanced Heterogeneous Integration, ICSJ 2024 156 - 157 2024

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Low-loss Subminiature Multimode Branched Polymer Optical Waveguide

Atsumi K., Azuma K., Ishigure T.

British and Irish Conference on Optics and Photonics, BICOP 2024 in Proceedings British and Irish Conference on Optics and Photonics 2024 2024

Loss Reduction of Single-mode Y-branched Polymer Optical Waveguide for MUX/DEMUX Devices in Mode Division Multiplexing Links

Sakai S., Ishigure T.

13th IEEE CPMT Symposium Japan: Innovation of Packaging Technology for Advanced Heterogeneous Integration, ICSJ 2024 200 - 203 2024

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Fixed Connection of Single-Mode Polymer Optical Waveguide with Single-Mode Optical Fiber

Toshida S., Ishigure T.

13th IEEE CPMT Symposium Japan: Innovation of Packaging Technology for Advanced Heterogeneous Integration, ICSJ 2024 164 - 165 2024

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Fabrication of GI core polymer optical waveguides enabling low loss with small bend radius (~1 mm) using high Δ resins

Karakawa M., Ishigure T.

British and Irish Conference on Optics and Photonics, BICOP 2024 in Proceedings British and Irish Conference on Optics and Photonics 2024 2024

Evaluation and Analysis of Polarization Dependent Polymer Optical Waveguide Characteristics

Wakabayashi T., Ishigure T.

13th IEEE CPMT Symposium Japan: Innovation of Packaging Technology for Advanced Heterogeneous Integration, ICSJ 2024 196 - 199 2024

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Direct Connection of Multimode Polymer Waveguide and Multimode Fibers Using the Mosquito Method

Nakamura T., Ishigure T.

13th IEEE CPMT Symposium Japan: Innovation of Packaging Technology for Advanced Heterogeneous Integration, ICSJ 2024 154 - 155 2024

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3D Polymer Optical Waveguide-based Fan-in/out Device for Silicon Photonics Chips

Ito A., Ishigure T.

13th IEEE CPMT Symposium Japan: Innovation of Packaging Technology for Advanced Heterogeneous Integration, ICSJ 2024 162 - 163 2024

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3D Polymer Optical Waveguide-based Fan-in/out Device for Silicon Photonics Chips

Ito A., Ishigure T.

British and Irish Conference on Optics and Photonics, BICOP 2024 in Proceedings British and Irish Conference on Optics and Photonics 2024 2024

Step and graded-index core-based polymer multimode interference splitters for photonic integrated circuits

Rasel M.O.F., Afsary N., Alam M.K., Tasnim F., Sakib M.N., Hatai R., Ishigure T.

Optik 290 2023.10

ISSN 00304026

This paper demonstrates step-index (SI) and graded-index (GI) core-based multimode interference (MMI) splitters realized with polymer materials for photonic integrated circuits (PICs). These SI and GI index-based MMI splitters guide the input light through the multimode waveguide following the self-imaging principles and demonstrate the multiple outputs with the same uniformity when the self-imaging length is obtained. We numerically design and develop (1 ×5) MMI splitters using the beam propagation method (BPM), and we use the RSoft CAD BeamPROP solver for the structural design and waveguide characterization. The structures of the SI and GI MMI splitters are optimized by investigating the structural parameters, particularly the width and length of the multimode waveguide and the core spacing between the output ports with the maximum uniform intensity at the self-imaging length. We also compare the structural design and optical properties of the SI and GI MMI waveguides. The excess losses of the SI MMI splitter are 1.09 and 1.12 dB for transverse electric (TE) and transverse magnetic (TM) modes, respectively, while for the GI MMI splitter, the losses are 0.57 dB and 0.56 dB for TE and TM modes, respectively at 1.55 µm. The power splitting efficiency for the SI MMI splitter is 77%, and for the GI MMI splitter, it is 88%. We also investigate the polarization dependence loss (PDL) for both MMI splitters, and the losses for the SI and GI MMI splitters are 0.024 dB and 0.004 dB, respectively.

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Fabrication of Circular Cross-Section Microchannels with 3-D Lattice Arrangement and Their Use as On-Off Valves

Uehara K., Hori Y., Ishigure T.

Micro 3 ( 3 ) 620 - 631 2023.09

In this paper, circular cross-section microchannels with 3-D lattice arrangements are designed and fabricated using the Mosquito method in order to construct on-off valves. The 3-D microchannels with on-off valves consist of two types of lines: the flow lines for chemical liquid flow and the control lines to activate the valves. We confirmed that both a circular cross-section and a PDMS with low elastic modulus used as the microchannel material contribute to a valve that can be closed with a lower pressure. Then, we demonstrated liquid flow to evaluate the functionality of the valve. Fluorescein solution was flown into a flow line. We found that the fluorescence intensity decreases at the intersection between the flow and control lines when the flow line is closed by the inflation of the control line, experimentally confirming the functionality of the valve microchannels fabricated via the Mosquito method.

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Graded-index core-based polarization beam splitters realized with symmetric polymer directional couplers

Tasnim F., Afsary N., Rasel M.O.F., Ishigure T.

Optics Continuum 2 ( 5 ) 1040 - 1052 2023.05

In this paper, we design and demonstrate polymer-based polarization beam splitters realized with parabolic graded-index (GI) directional couplers at 1550 nm. We design and investigate these beam splitters by using the beam propagation method (BPM) and the RSoft CAD BeamPROP solver is used for model design and characterization. We study the splitting ratio of 50:50 and 100:0 of these beam splitters for both transverse electric (TE) and transverse magnetic (TM) modes of the polarized light. In particular, the 50:50 beam splitters exhibit an output efficiency of 95% due to the absence of polarization. However, in the presence of the polarization effect, the polarization dependency is analyzed and manipulated successfully, and the output efficiency increases by approximately 98% at an incident angle of 31° due to the polarized launch field. Moreover, the 100:0 beam splitters act as the switching devices realized with parabolic GI polymer directional couplers. The insertion losses of the GI beam splitters are 0.162 dB and 0.186 dB, while the excess losses are 0.148 dB and 0.149 dB for TE and TM modes, respectively. Also, the polarization extinction ratio (PER) of the 100:0 beam splitters is >25 dB and >20 dB for TE and TM modes, respectively.

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VCSEL-based optical transceiver with a 90°-bent graded-index core polymer waveguide coupler for 25.78-Gb/s transmission

Kohmu N., Ishii M., Hatai R., Ishigure T.

Optics Continuum 2 ( 5 ) 998 - 1012 2023.05

In this paper, we propose a low-loss assembly of optical elements [vertical cavity surface emitting laser (VCSEL)/photodiode (PD)] and a 90°-bent graded-index (GI) core polymer optical waveguide for compact high-speed optical transceivers. The air gap between the 90°-bent GI-core waveguide and VCSEL/PD chips are filled with a high-index resin, and we demonstrate a reduction not only of the Fresnel reflection loss but also of the coupling loss due to the lower divergence angle of VCSEL and fiber output beams. In this paper, the core size and NA of the 90°-bent GI-core in the polymer waveguide are redesigned to match the specific launch conditions realized with the gap filled with resins, resulting in theoretical estimates of insertion losses as low as 0.82 dB and 1.38 dB for the waveguides on the transmitter and receiver sides, respectively. Such low insertion losses are obtained not by step-index core but GI core waveguides. After redesigning the structure, 90°-bent GI-core polymer waveguides with a bending radius of 1 mm are experimentally fabricated using the Mosquito method, and we experimentally demonstrate that the insertion loss of the waveguide can be reduced by about 4 dB when the 100-µm air gap is filled with an optical adhesive (na = 1.51). In addition, an error-free 25.78-Gb/s data transmission is successfully demonstrated over a 100-m MMF link using the fabricated VCSEL based transceivers with 90°-bent GI core polymer optical waveguides.

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Unique Optical Connect Structure with Polymer Waveguide Fabricated by the Mosquito Method

Furuta Y., Kondo F., Ito A., Ichinose R., Kaneda H., Fujii T., Ishigure T.

2023 IEEE CPMT Symposium Japan, ICSJ 2023 41 - 44 2023

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Temperature Dependence of Coupling Loss from SMF to Polymer Optical Waveguides with Various Refractive Index Profiles

Kinoshita R., Ishigure T.

2023 IEEE CPMT Symposium Japan, ICSJ 2023 172 - 175 2023

In this paper, we theoretically estimate the temperature dependence of coupling loss between single-mode (SM) polymer optical waveguides and general-purpose SM fiber (SMF), and discuss about the applicability of polymer optical waveguides to co-packaged optics (CPO). Although SM polymer optical waveguides are expected to be applied as an element of CPO, their small cores require precise mode-field adjustment with precise alignment of the cores. The mode-field and alignment positions of polymer waveguides are conce1ed to be affected by their operation temperature, particularly when integrated with Si photonics chips that could be a heat source. Simulation results show that the properties are maintained even under high-temperature operation.

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Tactile Pressure Sensor Based on Flexible Polymer Optical Waveguides Fabricated by the Mosquito Method

Yin Y., Ishigure T.

2023 IEEE CPMT Symposium Japan, ICSJ 2023 176 - 179 2023

In this paper, a polymer-based optical waveguide sensor is created to address several issues in optical fiber-based sensors. The unique feature of our optical waveguide is its 3-D core arranged design fabricated using the Mosquito method to which poly dimethyl siloxane (PDMS) is applied as the cladding for a flexible tactile sensor. The core monomer is dispensed into the PDMS monomer to have a 3D lattice structure. We demonstrate that the fabricated waveguide sensors exhibit a high repeatability of the pressure sensing. We find that the measurement range is from 0 MPa to 0.164 MPa when an organic inorganic hybrid resin, NP-C01-KO is used as the main core material. By examining the effect of the numerical aperture and the core size on the sensitivity, we confirm that bending loss could cause the output power variation when a load is applied to the sensor.

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Structural Investigation of Rare-Earth Metal Polymer Composite Doped Optical Amplifiers for Higher Gain

Ono K., Ishigure T.

2023 IEEE CPMT Symposium Japan, ICSJ 2023 125 - 126 2023

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Polymer Optical Waveguide Type 3-D MUX Device for Mode Division Multiplexing Links

Ichinose R., Kowatari T., Ishigure T.

2023 IEEE CPMT Symposium Japan, ICSJ 2023 208 - 211 2023

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Polymer Optical Waveguide Type 3-D MUX device for Mode Division Multiplexing Links

Ichinose R., Kowatari T., Ishigure T.

Proceedings - Electronic Components and Technology Conference 2023-May 1804 - 1808 2023

ISSN 05695503

In this paper, we fabricate a polymer optical waveguide with 3-dimensional core arrangement applicable to a MUX device for mode-division multiplexing technology. We apply the Mosquito method that we developed as a fabrication technique to fabricate single-mode and multimode polymer optical waveguides with circular cores. Because of the unique fabrication procedures of the Mosquito method, 3-dimensional core arrangement is possible, and thus a polymer optical waveguide with a functionality of MUX devices that can launch all the propagating modes in a few-mode fiber (FMF) can be fabricated. We emphasize that the different higher-order modes, LP11aand LP11b in one core could be individually excited using the fabricated waveguide type MUX devices.

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Polymer Optical Waveguide Coupler with Vertically Bent Cores

Itaru N., Kohmu N., Ishigure T.

2023 IEEE CPMT Symposium Japan, ICSJ 2023 89 - 92 2023

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Low Loss Design and Fabrication for Tapered Waveguide Based Spot Size Converter

Kondo F., Furuta Y., Kaneda H., Fujii T., Ishigure T.

2023 IEEE CPMT Symposium Japan, ICSJ 2023 168 - 171 2023

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Fabrication of Multimode Polymer Optical Waveguide Based Splitter by the Mosquito Method and Investigation of Its Signal Splitting Ratio

Azuma K., Ishigure T.

2023 IEEE CPMT Symposium Japan, ICSJ 2023 123 - 124 2023

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Error-Free Three-Dimensional Multimode Crossover Graded-Index Polymer Waveguides for Board-Level Optical Circuitry

Rasel M.O.F., Yamauchi A., Ishigure T.

Journal of Lightwave Technology 40 ( 19 ) 6465 - 6473 2022.10

ISSN 07338724

In this paper, we experimentally introduce a low-loss 3-dimensional (3D) symmetric crossover multimode optical waveguides realized with parabolic graded-index (GI) profiles using the Mosquito method. This compact crossover multimode waveguide is comprised of two S-bend core groups (6 Ch. × 6 Ch.), where the last six cores cross over the first six cores, maintaining a height gap at the crossover section to avoid the smudging from needle scan. The suitable height gap for this crossover multimode structure is 0.7 mm. The insertion loss of this multimode crossover waveguide is 1.64 dB at 850 nm wavelength. The insertion losses of this multimode crossover waveguide are compared with separately fabricated 3D S-bend waveguides, and it indicates that multimode crossover structures do not exhibit remarkable excess loss. The interchannel crosstalk of this waveguide is less than -45 dB. This crossover multimode waveguide demonstrates sharply open optical and electrical eye diagrams and transmits error-free data at 26 Gb/s.

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Formation of 3D Polymer Optical Waveguides

Yakabe S., Manabe K., Sasaki D., Ishigure T.

SEI Technical Review ( 95 ) 5 - 10 2022.10

ISSN 13434349

The Mosquito method, a polymer optical waveguide fabrication method invented by Professor Ishigure at Keio University, enables the three-dimensional (3D) formation of core patterns in cladding using a commercially available micro dispenser and a multi-axis syringe-scanning robot. This fabrication method is expected to be used to realize devices required for 3D waveguides such as Fan-in/Fan-out (FIFO) devices, which are essential for the introduction of multicore fibers (MCF). On the other hand, prior studies have mainly examined multimode waveguides, and several issues need to be solved for making single-mode devices. In particular, the core shape tends to deteriorate from circular due to monomer flow caused by needle scanning in the cladding, which is a factor that increases the connection loss with the optical fiber. This paper presents a theoretical and experimental study on the fabrication of single-mode waveguides by the Mosquito method and the formation of circular cores using the method to reduce connection loss with single-mode optical fibers.

Fabrication of Y-Branched GI Core Polymer Waveguide and its Application to CWDM MUX Device for Multimode Fiber

Hatai R., Nakazaki F., Nakayama T., Ishigure T.

Journal of Lightwave Technology 40 ( 9 ) 2915 - 2925 2022.05

ISSN 07338724

This paper describes the characteristics of graded-index (GI) core Y-branched polymer optical waveguides as optical couplers for multimode fibers (MMFs) in coarse wavelength division multiplexing links with a restricted mode launch function. In this paper, we compare two GI-core Y-branched waveguides fabricated using different methods: the Mosquito method and the imprint method. Error free transmission is confirmed when transmitting a 25.6125-Gbps NRZ optical signal (PRBS31) at 850-nm wavelength through a 100-m long OM3 fiber using the waveguide as an optical coupler. We also discuss the function of a restricted mode launch exciter for a 1-km long MMF. From the effective modal bandwidth analysis, realizing higher bandwidth-distance product in long MMFs should be possible by reducing the core size of the waveguide coupler.

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90°-bent graded-index core polymer waveguide for a high-bandwidth-density VCSEL-based optical engine

Kohmu N., Ishii M., Hatai R., Ishigure T.

Optics Express 30 ( 3 ) 4351 - 4364 2022.01

In this paper, we present a low-loss optical assembly utilizing a 90°-bent graded-index (GI) core polymer optical waveguide on vertical cavity surface emitting laser (VCSEL) based optical transceivers. The proposed assembly can replace conventional components such as mirrors and lenses for realizing subminiature optical engines applicable to on-board integration. To minimize the total insertion loss of the waveguide when connected to a high-speed VCSEL and a GI-core multimode fiber (MMF) at each end, the characteristics of the beam emitted from VCSELs are measured and taken into consideration for the waveguide design. In order to confirm the effect of insertion loss reduction by the waveguide numerical aperture control, 90°-bent GI-core polymer waveguides are fabricated applying the Mosquito method. The fabricated waveguide exhibits a total insertion loss as low as about 2 dB at 850-nm wavelength, which includes the coupling losses at both ends, bending, and propagation losses. We also investigate a way to reduce the insertion loss when a gap exists between the waveguide and VCSEL chip. We theoretically and experimentally confirm that filling the gap with a high index resin can reduce the coupling loss by 5 dB.

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Fabrication for single/few-mode Y-branch waveguide using the Mosquito method

Hatai R., Hama H., Ishigure T.

Optics Express 30 ( 3 ) 3524 - 3537 2022.01

In this paper, Y-branched circular core single-mode/few-mode polymer optical waveguides are designed and fabricated using the Mosquito method we have developed. They comprise a low loss multiplexing (MUX) device for mode division multiplexing. In the Mosquito method, since a liquid core monomer is dispensed into another liquid cladding monomer while the needle scans along the path of the wiring patterns, it was difficult to form in-plane core crossings and core branches. In this paper, to form single-mode/few-mode Y-branched cores, we apply a unicursal needle-scan path for the Y-branch structure with the Mosquito method. For MUX device applications, cores satisfying the single-mode condition are successfully formed on the two-port side while the one-port side has a few-mode core.

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High-Density Electrical and Optical Assembly for Subminiature VCSEL-Based Optical Engine

Kohmu N., Ishii M., Ishigure T.

IEEE Transactions on Components, Packaging and Manufacturing Technology 12 ( 1 ) 27 - 36 2022.01

ISSN 21563950

In this article, we propose a subminiature (10.9 mm $\times56.6$ mm) vertical cavity surface-emitting laser (VCSEL)-based optical engine with a low crosstalk penalty for onboard applications. When applying optical engines to onboard interconnects, ICs [laser drivers and transimpedance amplifiers (TIAs)] and active optical devices (light sources and photodetectors) must be mounted densely to make the footprint as small as possible. It is a concern that such a high-density integration could increase the crosstalk between transmitter (Tx) and receiver (Rx) devices, which could be caused by the supply current difference between the circuit from laser drivers to light source and the circuit from photodetectors to TIAs. In this article, by inserting a gap in the ground electrode, a compact optical engine (less than half of the footprint of quad small form-factor pluggable-double density (QSFP-DD) compliant engines) enabling a 25.78-Gb/s error-free optical transmission is successfully fabricated. We optimize the gap width to decrease the crosstalk while maintaining efficient heat dissipation via the electrode. We compare the characteristics of the fabricated optical engine to the engine with the gap-less ground electrode structure formed in the same compact size. Then, we both theoretically and experimentally confirm a link power budget savings of about 1.8 dB, which is sustained even under high-temperature ( $T_{c} = 70\,\,^{\circ }\text{C}$ ) operation. In addition, to realize further high-density assembly, we also represent a lens-less optical coupling by inserting a 90o-bent graded-index (GI) core polymer waveguide between the optical transmitter and multimode fiber. The transmission performance of the 90o-bent GI-core waveguide is preliminarily evaluated, and we successfully transmit 53.125-Gb/s PAM4 optical signals experimentally.

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Single-mode polymer waveguide for fan-in/fan-out of multicore fiber by the mosquito method

Yakabe S., Ishigure T.

Proceedings of SPIE - The International Society for Optical Engineering 12007 2022

ISSN 0277786X

In this paper, in order to apply to optical connection components such as fan-in-fan-out (FIFO) devices for multicore fibers (MCFs), we design polymer optical waveguides with circular cores satisfying the single-mode condition, which are fabricated using the Mosquito method, and experimentally demonstrate that the optimum S-shape bent core waveguide can be fabricated as designed. The Mosquito method is a technique we have developed to form circular cores in both multimode and single-mode waveguides using a commercially available microdispenser and multi-axis syringe scanning robot. We have demonstrated that single-mode waveguides fabricated by the Mosquito method can be coupled with SMF with low loss. However, in order to realize a waveguide type FIFO device for MCFs by the Mosquito method, it is necessary to maintain micron-order positioning accuracy for the cores while three dimensionally aligning multiple cores in FIFO patterns. Since the pitch between the cores on the MCF side is very narrow, the core position is likely to deviate from the design value due to the liquid monomer flow caused by needle scan. We statistically confirm the possible amount of deviation from the design position by needle scan and feed it back to the program of needle scan path for the FIFO. We successfully fabricate a four-core FIFO with a desired core pitch. It is experimentally confirmed that the insertion loss is 1.4 dB on average. From these investigations, we confirm that the Mosquito method has an ability to fabricate small and low-loss FIFO devices.

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Investigation of fabrication conditions for Y-branched polymer optical waveguides using the Mosquito method

Sekitani K., Hatai R., Ishigure T.

2022 IEEE CPMT Symposium Japan, ICSJ 2022 100 - 101 2022

In this paper, the conditions for fabricating Y-branched optical waveguides using the Mosquito method are discussed, focusing on the viscosity of the monomer and the branch angle. With increasing the viscosity of core monomer, the Y-branching structures tend to be distorted particularly when the branching angle is larger than 0.5 degree. After finding out the appropriate fabrication conditions, Y-branched optical waveguides in which two-port cores are vertically stacked are fabricated, taking the advantage of the Mosquito method: the ability to form three-dimensional core wiring patterns. Single-mode and multimode cores are successfully formed in which we could confirm the light propagation.

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GI-core Multimode and Single-mode Polymer Waveguides for High-density Co-packaging

Ishigure T.

2022 Optical Fiber Communications Conference and Exhibition, OFC 2022 - Proceedings 2022

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GI-core Multimode and Single-mode Polymer Waveguides for High-density Co-packaging

Ishigure T.

Optics InfoBase Conference Papers 2022

Fabrication for Y-branched Polymer Optical Waveguide Using the Imprint Method and Its Application for Mode Division Multiplexing Devices

Ono S., Ishigure T.

2022 IEEE CPMT Symposium Japan, ICSJ 2022 45 - 48 2022

We propose an asymmetric polymer Y-branched waveguide for a multiplexer of TE01 and TE11 modes to a few-mode fiber in mode division multiplexing links, in this paper. Fabricated waveguides have square cross-sectional graded-index (GI) cores which exhibit strong optical confinement to the core center. Theoretical loss calculation by BPM shows that the GI core exhibits higher mode splitting ratio and about 1 dB lower insertion loss than the conventional SI core. The measurement results of the fabricated waveguide elucidate that the GI core shows an insertion loss about 1.5 dB lower than the SI core, showing a more pronounced low loss advantage. We also demonstrate in this paper that a square approximation for the core cross-section allows to reduce the coupling loss with fibers and realize a low-loss mode multiplexer, compared to the rectangular cross-sectional core.

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Fabrication for Polymer Optical Waveguide and Its Application for Co-Packaged Optics

Ishigure T.

Journal of Japan Institute of Electronics Packaging 25 ( 2 ) 157 - 161 2022

ISSN 13439677

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Fabrication for low-loss polymer optical waveguide with vertically 90° bent core

Suemori D., Ishii M., Kohm N., Ishigure T.

2022 IEEE CPMT Symposium Japan, ICSJ 2022 92 - 93 2022

In this paper, we directly fabricate vertically 90-degree bent core polymer optical waveguide right above a VCSEL chip to be applied to an optical coupler in subminiature on-board optical engine. We have proposed the Mosquito method for fabricating polymer optical waveguide utilizing a microdispenser. In the procedure of the Mosquito method, the vertically 90-degree bent cores are dispensed just above VCSEL chips by taking the advantage of the Mosquito method: ability to form three-dimensional core wiring pattern. We emphasize in this paper that the number of the vertically bent core is increased to three that are aligned in parallel and small bending radius with the 3 parallel core structure can be formed.

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Fabrication for Circular Cross-Sectional Microchannels and Their Application for On-off Valves

Uehara K., Hori Y., Ishigure T.

2022 IEEE CPMT Symposium Japan, ICSJ 2022 119 - 122 2022

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Design and Fabrication of Three-dimensional Polymer Optical Waveguide-based Fan-in/out Device for Multicore Fibers

Yamaguchi Y., Yakabe S., Ishigure T.

2022 European Conference on Optical Communication, ECOC 2022 2022

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Design and Fabrication of Three-dimensional Polymer Optical Waveguide-based Fan-in/out Device for Multicore Fibers

Yamaguchi Y., Yakabe S., Ishigure T.

2022 IEEE CPMT Symposium Japan, ICSJ 2022 41 - 44 2022

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90-degree bent core polymer optical waveguide coupler for low loss lens-less light coupling between laser / photodetector and fiber

Suemori D., Ishii M., Kohmu N., Ishigure T.

Proceedings - Electronic Components and Technology Conference 2022-May 436 - 440 2022

ISSN 05695503

In this paper, we present direct fabrication of vertically 90-degree bent core polymer optical waveguide couplers to be integrated in optical engines enabling lens-less light coupling between laser source / photodetector and fiber with low loss. We apply the Mosquito method that we developed as a fabrication technique for single-mode and multimode polymer optical waveguides with circular cores. Because of the unique fabrication procedures of the Mosquito method, three-dimensional core alignment is possible, and thus 90° bent core can be formed directly on a laser chip. We would like to emphasize that the bending radius as small as 2 mm or less could be formed, while the insertion loss of the waveguide is as low as 5 dB.

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Waveguide length and pump power effects on the amplification of europium aluminum doped polymer

Saris N.N.H., Yoshida Y., Horie T., Hamzah A., Ambran S., Mikami O., Ishigure T., Fukui T.

Optik 239 2021.08

ISSN 00304026

Mosquito method is used to fabricate a 50 μm core diameter graded index (GI) multimode Eu-Al doped polymer composite optical waveguide amplifier. In this paper, waveguide length and pump power are varied with an input signal of - 30 dB m. Under a 532 nm laser excitation, 16.27 dB optical gain under an optimal 10 cm waveguide length is observed from forward pumping amplification for a threshold pump power of 23 dB m. Also, the waveguide has been characterized to be 0.83 dB/cm at 617 nm wavelength.

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Mosquito method based polymer tapered waveguide as a spot size converter

Kobayashi Y., Sakaguchi Y., Yasuhara K., Ishigure T.

Optics Express (Optics Express) 29 ( 6 ) 9513 - 9531 2021.03

We create a compact low-loss spot-size converter (SSC) which utilizes a tapered core polymer optical waveguide with circular cross-sectional graded-index (GI) core using the Mosquito method we developed. First, we theoretically analyze the mutual diffusion between the core and cladding monomers, which is a feature unique to the Mosquito method when forming GI cores. The monomer diffusion effect depends on the initial core diameter that is dispensed by a microdispenser and the diffusion time before UV curing: in a small core the monomer diffuses more rapidly than in a large core. Using this diffusion dependence on the initially dispensed core diameter, it is theoretically found that a tapered polymer waveguide based SSC can adiabatically convert the mode-field diameter between 4.0 and 8.6 µm at a 1550-nm wavelength waveguide as short as 4 mm. Next, the tapered waveguide based SSC with the designed structure is experimentally fabricated using the Mosquito method, and we confirm an 8-mm long tapered waveguide with an insertion loss of 1.83dB functions as a SSC that converts the MFD from 4.7 µm to 7.5 µm at 1550-nm wavelength.

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Low loss single-mode polymer optical waveguide with circular cores

Yakabe S., Kobayashi Y., Matsui H., Saito Y., Manabe K., Ishigure T.

OSA Continuum (OSA Continuum) 4 ( 3 ) 1070 - 1085 2021.03

We experimentally demonstrate that the Mosquito method is capable of fabricating single-mode polymer optical waveguides with multiple cores while maintaining an identical mode-field diameter among them. The Mosquito method we developed is a technique to form circular cores in polymer waveguides using a commercially available microdispenser and multi-axis syringe scanning robot. However, the core shape tends to deteriorate from a circle because of the monomer flow due to the needle scan. We also demonstrate both theoretically and experimentally for the first time in this paper that the needles with a tapered outer form or just titled straight needles enable to form cores with a high circularity even if those cores are dispensed on any heights from the substrate surface.

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Multi-Channel Single-Mode Polymer Waveguide Fabricated Using the Mosquito Method

Yakabe S., Matsui H., Kobayashi Y., Saito Y., Manabe K., Ishigure T.

Journal of Lightwave Technology (Journal of Lightwave Technology) 39 ( 2 ) 547 - 556 2021.01

ISSN 07338724

We experimentally demonstrate that the Mosquito method is capable of fabricating polymer optical waveguides with single-mode cores. The Mosquito method we developed is a technique to form planar polymer waveguides using a commercially available microdispenser. In this article, the flow of the core monomer dispensed from the tip of the needle is simulated using fluid analysis software. The results show that the shape of the needle periphery significantly affects the fabrication of perfectly circular cross-sectional cores. In addition, we demonstrate that the Mosquito method is capable of reducing the MFD variation to 0.4 μm. We find such a small MFD fluctuation is comparable to that of typical single-mode optical fibers.

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Multiplexing Coupler Realized with Y-branched GI Core Polymer Optical Waveguide for Mode Division Multiplexing in a 50-μm Multimode Fiber

Hatai R., Ishigure T.

Proceedings - Electronic Components and Technology Conference 2021-June 1682 - 1688 2021

ISSN 05695503

In this paper, a novel structure for a multimode Y-branched polymer waveguide type multiplexer (MUX) device for mode division multiplexing (MDM) is proposed. Since the insertion loss of GI core Y-branched waveguides remains low even with the tilted launch beam or a small size of cross-sectional core, we have proposed asymmetric Y-branched MUX device which has different core size at the end of two-port arm. In this paper, we investigate the optimum structure of the asymmetric Y-branched waveguides MDM MUX device using a beam propagation simulation.

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Multimode Interference based Y-Branch Polymer Optical Waveguide Splitter: Design and Investigation

Alam M.K., Afsary N., Rasel M.O.F., Ishigure T.

Proceedings of International Conference on Electronics, Communications and Information Technology, ICECIT 2021 2021

We demonstrate multimode interference (MMI)-based Y-branch single-mode step-index (SI) core polymer optical waveguide splitter for the development of optical circuitry. This polymer waveguide splitter consists of a single input and multiple (six) outputs realized with organic-inorganic hybrid polymer materials. We set the core width for input and outputs of this polymer waveguide splitter as a single-mode, where the core width is particularly 6.5 mumathrm{m}. We design and demonstrate this Y-branch waveguide splitter using the beam propagation method at 1550-nm wavelength following the self-imaging principle. The power efficiency of this MMI-based Y-branch polymer waveguide splitter is 71%, and the excess loss is 1.4 dB.

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High-efficiency optical coupling between VCSEL and 90-degree-bent Graded-Index Core Polymer Waveguide with Numeral Aperture Optimization

Kohmu N., Ishii M., Ishigure T.

2021 IEEE CPMT Symposium Japan, ICSJ 2021 150 - 153 2021

In this paper, we propose a higher efficiency optical coupling technique using 90-degree-bent Graded-Index (GI) core polymer waveguide which replaces conventional optical assembly (mirrors and lenses) in vertical cavity surface emitting laser (VCSEL) based optical engines. The 90-degree-bent GI-core polymer waveguides are fabricated using the Mosquito method. However, high coupling loss could be caused by the VCSEL beam divergence due to diffraction in the lens free coupling. We theoretically confirm that total insertion loss including bending loss as well as coupling loss could remain low by the waveguide NA control. Fabricating the 90-degree-bent GI-core polymer waveguides with the optimized NA, a waveguide insertion loss as low as about 2 dB is experimentally achieved.

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Development of 3-Dimensional Single-mode Core Over-Crossing Polymer Optical Waveguides Using the Mosquito Method

Rasel M.O.F., Ishigure T.

2021 IEEE CPMT Symposium Japan, ICSJ 2021 188 - 191 2021

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Design and Fabrication of Y-branched Polymer Waveguide based Optical Coupler

Hatai R., Hama H., Ishigure T.

2021 IEEE CPMT Symposium Japan, ICSJ 2021 184 - 197 2021

We propose multiplexer devices in short wavelength range wavelength division multiplexing (SWDM) and mode division multiplexing (MDM) systems as applications of graded-index core Y-branched polymer waveguides. We demonstrate 25-Gbps optical signal transmissions at wavelengths of 850 nm and 1060 nm over an MMF via a Y-branched waveguide as an SWDM multiplexer (MUX) device. For an MDM MUX device, a few-mode scale asymmetric Y-branched waveguide is experimentally fabricated and the optical fields of multiple modes transmitted in the waveguide are confirmed.

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Guanine crystals regulated by chitin-based honeycomb frameworks for tunable structural colors of sapphirinid copepod, Sapphirina nigromaculata

Kimura T., Takasaki M., Hatai R., Nagai Y., Uematsu K., Oaki Y., Osada M., Tsuda H., Ishigure T., Toyofuku T., Shimode S., Imai H.

Scientific Reports (Scientific Reports) 10 ( 1 ) 2020.12

© 2020, The Author(s). Sapphirinid copepods, which are marine zooplankton, exhibit tunable structural colors originating from a layered structure of guanine crystal plates. In the present study, the coloring portion of adult male of a sapphirinid copepod, Sapphirina nigromaculata, under the dorsal body surface was characterized to clarify the regulation and actuation mechanism of the layered guanine crystals for spectral control. The coloring portions are separated into small domains 70–100 µm wide consisting of an ordered array of stacked hexagonal plates ~1.5 µm wide and ~80 nm thick. We found the presence of chitin-based honeycomb frameworks that are composed of flat compartments regulating the guanine crystal plates. The structural color is deduced to be tuned from blue to achromatic via yellow and purple by changing the interplate distance according to vital observation and optical simulation using a photonic array model. The framework structures are essential for the organization and actuation of the particular photonic arrays for the exhibition of the tunable structural color.

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Polarization Dependence of Optical Properties of Single-Mode Polymer Optical Waveguides Fabricated under Different Processes at 1310/1550 nm

Morimoto Y., Matsui H., Hikita M., Ishigure T.

Journal of Lightwave Technology (Journal of Lightwave Technology) 38 ( 14 ) 3670 - 3676 2020.07

ISSN 07338724

We experimentally investigate the polarization dependence of the optical properties of single-mode polymer optical waveguides. We compare two types of waveguides composed of the same polymer materials: Step-index square-core waveguides fabricated using the direct curing method and graded-index (GI) circular-core waveguides fabricated using the Mosquito method. We demonstrate that the GI circular-core single-mode waveguides exhibit remarkably small dependence of optical loss on the polarization angle, which is less than 0.1 dB polarization dependent loss (PDL) at both 1310 and 1550 nm wavelengths. This steady polarization property is attributed to the material stress free to the composing polymers during the fabrication process of the Mosquito method and to parabolic GI profile formed in symmetric circular core.

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Investigations on europium aluminum incorporated polymer composite optical waveguide amplifier

Najahatul Huda Saris N., Hamzah A., Sabri S., Ambran S., Mikami O., Ishigure T.

Journal of Physics: Conference Series (Journal of Physics: Conference Series) 1502 ( 1 ) 2020.06

ISSN 17426588

The gain performance of 50-iun core diameter graded-index (GI) multimode europium aluminum benzyl methacrylate (Eu-Al/BzMA) waveguide was investigated by numerically solving rate and propagation equations using MATLAB. At a fixed waveguide length of 10 cm and gain medium concentration of 13 wt.%, optical gain was found to be dependent on pump power and input signal power. This paper utilized a 532 nm wavelength pump with power varied from 100 mW to 500 mW, together with low (-30 dBm) and high (0 dBm) input signal powers, within the amplification range of 580 to 640 nm wavelength. With the highest pumping power of 500 mW and the lowest input signal power of -30 dBm, a 29-dB optical gain with wavelength of 617 nm was observed from forward pumping amplification. For comparison, an identical waveguide in terms of properties was fabricated through an innovative fabrication method for polymer waveguide - the Mosquito method. The fabricated waveguide was then experimentally tested for -30 dBm input signal power with 200 mW pump power in the attempt to realize future real-world applications of short reach networks such as in Local Area Network (LAN) and in-vehicle optical interconnects.

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Multi-Channel Single-mode Polymer Waveguide Fabricated by the Mosquito Method Realizing Low Connection Loss with Single-mode Optical Fiber Arrays

Yakabe S., Matsui H., Kobayashi Y., Ishigure T.

Proceedings - Electronic Components and Technology Conference (Proceedings - Electronic Components and Technology Conference) 2020-June 156 - 161 2020.06

ISSN 9781728161808

In this paper, we design a polymer waveguide to satisfy the single-mode condition and fabricate it using the Mosquito method. In order to apply the single-mode waveguides as a connection component with single-mode fibers (SMFs) or with other optical components such as laser / photodetector arrays, there are many issues such as the core shape, the mode-field diameter (MFD) variation, and the accuracy of the core position and pitch.Hence, we experimentally and theoretically demonstrate that the Mosquito method is capable of fabricating polymer optical waveguides with single-mode cores and the above issues on the single-mode connections are addressed in this paper.

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Integrated Optics Europium Aluminum Polymer Optical Waveguide with Graded Index Circular Core

Saris N.N.H., Kadir N.A.A., Hamzah A., Ambran S., Mikami O., Horie T., Ishigure T.

2020 IEEE 8th International Conference on Photonics, ICP 2020 (2020 IEEE 8th International Conference on Photonics, ICP 2020) 20 - 21 2020.05

ISSN 9781728105185

A Europium Aluminum Benzyl Methacrylate (Eu-Al/BzMA) integrated optical waveguide with 50 μm graded-index multimode circular core is fabricated by applying the Mosquito method for the potential application of optical interconnect. The parabolic index profile of the waveguide core is measured to confirm the profile exhibited by the waveguide. A preliminary experiment of the signal transmission is performed at 26 Gb/s to evaluate its capability in high dense and speed optical interconnections. According to the results, the waveguide successfully demonstrated free bit-error-rate through 5 cm waveguide transmission.

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Optical Amplification in Multiple Cores of Europium Aluminium Composite Incorporated Polymer-Based Optical Waveguide Amplifier by Using Mosquito Method

Saris N.N.H., Hamzah A., Ambran S., Mikami O., Ishigure T., Fukui T.

Lecture Notes in Electrical Engineering (Lecture Notes in Electrical Engineering) 619 25 - 34 2020

ISSN 9789811512889

© 2020, Springer Nature Singapore Pte Ltd. In this paper, Europium Aluminum Benzyl Methacrylate (Eu–Al/BzMA) optical waveguide amplifier is fabricated with multiple cores of 50 μm diameters by a unique procedure known as the Mosquito method which, utilized a micro-dispenser desktop machine. The waveguides which used the optimum dispensing criteria to fabricate desired core diameter with high precision are then optically tested. The highest optical gain of 1.08 dB/cm with 0.77 dBm/cm insertion loss has been demonstrated in this device at 617 nm amplification wavelength. Suppression of concentration quenching, high compatibility with other materials, ease of fabrication, and low cost make such rare-earth-metal ion-incorporated polymer waveguide amplifiers suitable for providing gain in many integrated optical devices in the communication area.

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Performance of europium Aluminium doped polymer optical waveguide amplifier

Saris N.N.H., Hamzah A., Ambran S., Mikami O., Ishigure T.

Bulletin of Electrical Engineering and Informatics (Bulletin of Electrical Engineering and Informatics) 8 ( 4 ) 1343 - 1350 2019.12

ISSN 20893191

© 2019 Institute of Advanced Engineering and Science. All rights reserved. In this paper, the graded index (GI) multimode rare-earth metal (RE-M) doped polymer optical waveguide amplifier has been prepared and tested optically. A 10-cm Europium Aluminum Benzyl Methacrylate (EuAl3O3/BzMA)was fabricated via a unique technique known as the “Mosquito Method” which utilizes a micro-dispenser machine. Optical gain from 75 to 150 μm circular core diameter waveguide of 13 wt.% concentration has been demonstrated and measured under forward pumping condition. The cladding monomer deployed in this research is Acrylate resin XCL01, which is a modified photocurable acrylate material. Fundamentally, -30 decibel (dBm) red light signal input and 23 dBm pump power of 532 nm green laser wavelength is implemented within the range of 580 to 640 nm optical amplification wavelength. A maximum gain of 12.96 dB at 617 nm wavelength has been obtained for a 100 μm core diameter of Eu-Al polymer optical waveguide. The effect of different coupler diameter for pumping and the comparison of insertion loss before and after amplification against the performance of the Eu-Al polymer waveguide amplifier are also studied. There exists an optimum core diameter of which the amplifier gain enhancement is at maximum value.

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Fabrication for Mode Coupling Optical Waveguide using the Mosquito Method

Kowatari T., Ishigure T.

2019 IEEE 2nd British and Irish Conference on Optics and Photonics, BICOP 2019 (2019 IEEE 2nd British and Irish Conference on Optics and Photonics, BICOP 2019) 2019.12

ISSN 9781728149486

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Fabrication for Single-Mode Core Fan-in/Out Polymer Optical Waveguide using the Mosquito Method

Matsui H., Yakabe S., Ishigure T.

2019 IEEE 2nd British and Irish Conference on Optics and Photonics, BICOP 2019 (2019 IEEE 2nd British and Irish Conference on Optics and Photonics, BICOP 2019) 2019.12

ISSN 9781728149486

© 2019 IEEE. We have developed the Mosquito method for fabricating polymer optical waveguides. By using the Mosquito method, three-dimensional array of circular cores with graded-index (GI) profile can be formed. In this paper, to realize an effective coupling element for multicore fibers (MCF) and singlemode fibers, fan-in/out polymer optical waveguides are focused. For low-loss fan-in/out waveguide, the Mosquito method is applied where the fabrication conditions are investigated to improve the optical properties in multiple cores. Furthermore, fan-in/out structure for 7-core MCF is successfully fabricated.

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Fabrication for Single-Mode Tapered Optical Waveguides for Spot-Size-Converter

Kobayashi Y., Sakaguchi Y., Ishigure T.

2019 IEEE 2nd British and Irish Conference on Optics and Photonics, BICOP 2019 (2019 IEEE 2nd British and Irish Conference on Optics and Photonics, BICOP 2019) 2019.12

ISSN 9781728149486

© 2019 IEEE. For low-loss connection between silicon waveguides and conventional single-mode fibers, single-mode tapered polymer optical waveguides are fabricated using the Mosquito method, which work as a spot-size converter (SSC). In this research, the axially tapered shaped core is formed by accelerating the needle scan during the core dispense. In addition, the degradation of cross-sectional core shape from circle to ellipse is addressed by using a curved needle. The fabricated 12-mm long tapered waveguide with perfect circular core cross section exhibits an effective MFD conversion from 4.1 μm to 8.1 μm.

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Simulation of refractive index profile formed in polymer optical waveguides fabricated using the Mosquito method

Sakaguchi Y., Ishigure T.

2019 IEEE CPMT Symposium Japan, ICSJ 2019 (2019 IEEE CPMT Symposium Japan, ICSJ 2019) 145 - 146 2019.11

ISSN 9781728109787

© 2019 IEEE. In polymer optical waveguides fabricated using the Mosquito method, the diffusion occurs between the core and cladding monomers during the interim time that is from the moment that the liquid core monomer is dispensed to when the UV curing begins, and a graded-index type refractive index profile is formed in the core. In this paper, the diffusion coefficient of monomer is measured. Then, a diffusion simulation model is created, which can calculate the concentration distribution of monomer using the diffusion coefficient that depends on the monomer concentration. Finally, the refractive index profiles formed in the cores are simulated and the output near-field patterns are theoretically estimated to evaluate the core diameter and numerical aperture dependences on the interim time.

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A 53-Gbit/s/ch Active Optical Cable Utilizing GI Polymer Waveguide for High-density On-board Optical Interconnects

Kohmu N., Ishii M., Ishigure T.

2019 IEEE CPMT Symposium Japan, ICSJ 2019 (2019 IEEE CPMT Symposium Japan, ICSJ 2019) 31 - 34 2019.11

ISSN 9781728109787

© 2019 IEEE. In this paper, we propose a low loss and cost-effective assembly in optical transceiver for on-board applications by applying graded-index (GI) core polymer waveguides to effectively couple the signal light between light sources/photodetectors and multimode fibers (MMFs). In order to satisfy the requirements for higher bandwidth data transmission, on-board optical interconnects have been anticipated in datacenter networks. When applying active optical cables (AOCs) to the on-board interconnects, the assembly density between optical devices and fibers is an important issue. Hence, polymer optical waveguides with densely aligned cores are one of the promising candidates to be an interface between the active components and fibers. In this paper, GI circular core polymer optical waveguides are applied to the onboard wiring. We demonstrate the ability of GI core waveguide to achieve low-loss coupling with optical transceivers due to tightly confined optical field in the core. Furthermore, we propose to utilize the lens function of GI core in the transceiver assembly. We theoretically demonstrate that the GI core enables to improve the coupling efficiency by 0.6 dB as a cylindrical lens. Meanwhile, by just inserting a perpendicularly bent GI core waveguide between an optical transmitter and an MMF, we successfully transmit a 53.125-Gbit/s PAM4 optical signals experimentally.

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Applicability of the Mosquito method to fabricate fan-in/out device for single-mode multicore fiber

Matsui H., Yakabe S., Ishigure T.

2019 IEEE CPMT Symposium Japan, ICSJ 2019 (2019 IEEE CPMT Symposium Japan, ICSJ 2019) 63 - 66 2019.11

ISSN 9781728109787

© 2019 IEEE. We have proposed the Mosquito method for fabricating polymer optical waveguides. By applying the Mosquito method, three-dimensional multimode and even single-mode graded-index (GI) circular cores can be formed. In this paper, for fabricating low-loss fan-in/out waveguide using the Mosquito method, the fabrication conditions are investigated to improve the uniformity of optical characteristics in multiple cores. Furthermore, the hexagonally arrayed single-mode cores are formed under a precise temperature control.

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Fabrication and Evaluation for Polymer Waveguide Optical Amplifier Incorporated with Rare Earth-Metal Polymer Composite

Horie T., Fukui T., Ishigure T.

2019 IEEE CPMT Symposium Japan, ICSJ 2019 (2019 IEEE CPMT Symposium Japan, ICSJ 2019) 167 - 168 2019.11

ISSN 9781728109787

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Fabrication for polymer microchannels with circular cross-section using photo-curable PDMS

Nakazawa R., Ishigure T.

2019 IEEE CPMT Symposium Japan, ICSJ 2019 (2019 IEEE CPMT Symposium Japan, ICSJ 2019) 119 - 122 2019.11

ISSN 9781728109787

© 2019 IEEE. In this paper, microchannels with circular cross-sections are fabricated using the Mosquito method in order to mimic microvascular networks. We experimentally confirm that microchannels with straight and Y-branched channel patterns are fabricated by applying photo curable PDMS(poly dimethyl siloxane) to the Mosquito method. Compared to our previous trials with heat-curable PDMS, the photo-curable PDMS allows to fabricate the microchannels in one-third of curing time. Finally, liquid flow in the fabricated Y-branched microchannels is confirmed by flowing water with red-colored pigment: the water with pigment is injected to a channel from the two-port side and the state of the liquid flow in the microchannel is observed.

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MMF Exciter Composed of Graded-Index Core Polymer Optical Waveguide Fabricated Applying the Mosquito Method and the Imprint Method

Hatai R., Nakazaki F., Nakayama T., Ishigure T.

2019 IEEE CPMT Symposium Japan, ICSJ 2019 (2019 IEEE CPMT Symposium Japan, ICSJ 2019) 133 - 134 2019.11

ISSN 9781728109787

© 2019 IEEE. In this paper, we evaluate the optical properties of low-loss Y-branched multimode polymer optical waveguide couplers with graded-index (GI) cores fabricated by different methods: the Mosquito method and the imprint method in order to apply them to coarse wavelength division multiplexing (CWDM) transmission. We confirm the low insertion loss of those waveguides regardless of fabrication method in a wavelength range from 850 to 1060 nm for CWDM. Furthermore, we succeeded in transmitting a 26 Gbps signal through the GI waveguide at 850-nm wavelength.

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Polarization dependence analysis of polymer optical waveguides

Morimoto Y., Matsui H., Hikita M., Ishigure T.

2019 IEEE CPMT Symposium Japan, ICSJ 2019 (2019 IEEE CPMT Symposium Japan, ICSJ 2019) 183 - 186 2019.11

ISSN 9781728109787

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Y-branched multimode/single-mode polymer optical waveguides for low-loss WDM MUX device: Fabrication and characterization

Ishigure T., Nakayama T., Nakazaki F., Hama H.

Proceedings - Electronic Components and Technology Conference (Proceedings - Electronic Components and Technology Conference) 2019-May 550 - 555 2019.05

ISSN 9781728114989

© 2019 IEEE. In this paper, we represent low-loss Y-branched multimode polymer optical waveguides with graded-index (GI) cores applicable to an optical coupler as a MUX device in coarse wavelength division multiplexing links. We apply the Mosquito method as well as the imprint method to form the Y-branched structures in polymers. We experimentally confirm that the insertion loss (including the coupling, propagation, bending, and multiplexing losses) in the multimode GI-core Y-branched waveguide is approximately 1-dB lower than the same Y-branched waveguide with step-index (SI) core. In addition, we also succeeded in fabricating Y-branched single-mode polymer waveguides applying the Mosquito method. In order to satisfy the single-mode condition, the core diameter needs to decrease to 10 mm and less.

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Design for polymer optical waveguides realizing efficient light coupling via 45-degree mirrors

Morimoto Y., Ishigure T.

Optics Express (Optics Express) 27 ( 8 ) 10839 - 10853 2019.04

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement We design graded-index (GI) circular-core waveguides to realize low-loss light coupling via 45-degree mirrors using a ray-trace simulator. The waveguide’s structural parameters, which determine the insertion loss of the waveguides with 45-degree mirrors, are the cladding thickness, the core size, the refractive index of materials, and the mirror angle. The optimum waveguide structural parameters are determined, and the GI circular-core waveguide with the appropriate structural parameters which is actually fabricated exhibits much lower total link loss than step-index (SI) core waveguides. The tight optical confinement of the GI-core contributes to the reduction of loss increment due to the mirror structure.

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Structural Design and Fabrication for Low Loss Y-branched Polymer Waveguide Coupler Devices

Nakazaki F., Ishigure T.

2018 British and Irish Conference on Optics and Photonics, BICOP 2018 - Proceedings (2018 British and Irish Conference on Optics and Photonics, BICOP 2018 - Proceedings) 2019.03

ISSN 9781538673614

© 2018 IEEE. Along with the wide deployment of cloud computing services, the introduction of optical interconnect technology has supported the rapid growth of data throughput in datacenter over the last couple of years. So far, multimode fiber (MMF) links have been widely installed in datacenter networks, hence the limitation of bandwidth distance product of MMF links is a current issue. In the future, wavelength division multiplexing (WDM) transmission technology could be applied even to the MMF links, by which the transmission capacity could increase because multiple optical signals with different wavelengths are multiplexed in one fiber.In, this paper, Y-branched polymer optical waveguide couplers with SI and GI square cores are fabricated using the imprint method in order to apply to a multiplexing (MUX) device in the MMF WDM links. To fabricate low loss MUX devices, three different Y-branch structures are designed and actually fabricated. Then, their optical characteristics are compared. It is confirmed that the loss of GI waveguide is lower than that of SI waveguide, independent of the multiplexing structure, because the light leakage at the multiplexing region (two-cores junction) could be reduced due to the strong light confinement effect.

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Application of GI polymer optical waveguide to coupling devices between multimode fiber and VCSEL

Hatai R., Ishigure T.

2018 British and Irish Conference on Optics and Photonics, BICOP 2018 - Proceedings (2018 British and Irish Conference on Optics and Photonics, BICOP 2018 - Proceedings) 2019.03

ISSN 9781538673614

© 2018 IEEE. In this paper, required specifications to a polymer waveguide based compact restricted mode launch (RML) device for multimode fibers are investigated. We confirm that a smaller spot size on the MMF launch end is necessary to enhance the effective modal bandwidth (EMBc), whereas a lower numerical aperture does not always allow the high EMBc. In addition, we determine the design guideline of polymer waveguide based RML exciters using the beam propagation method simulation.

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Application of the Mosquito Method to Polymer Optical Coupling Devices

Nakamura J., Ishigure T.

2018 British and Irish Conference on Optics and Photonics, BICOP 2018 - Proceedings (2018 British and Irish Conference on Optics and Photonics, BICOP 2018 - Proceedings) 2019.03

ISSN 9781538673614

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3-Dimensional channel-shuffling single-mode polymer waveguides: Design and fabrication

Rasel O., Ishigure T.

2018 IEEE CPMT Symposium Japan, ICSJ 2018 (2018 IEEE CPMT Symposium Japan, ICSJ 2018) 143 - 144 2019.01

ISSN 9781538654422

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Low-loss single-mode polymer optical waveguides: Comparison between direct-curing and the mosquito methods

Morimoto Y., Hikita M., Matsui H., Fujihara Y., Ishigure T.

2018 IEEE CPMT Symposium Japan, ICSJ 2018 (2018 IEEE CPMT Symposium Japan, ICSJ 2018) 145 - 146 2019.01

ISSN 9781538654422

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Application of the mosquito method for implementing waveguides on surface emitting light sources

Nakamura J., Ishigure T.

2018 IEEE CPMT Symposium Japan, ICSJ 2018 (2018 IEEE CPMT Symposium Japan, ICSJ 2018) 123 - 124 2019.01

ISSN 9781538654422

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Direct fabrication for multimode/single-mode polymer optical waveguides on printed circuit board using the mosquito method

Marushima C., Ishigure T.

2018 IEEE CPMT Symposium Japan, ICSJ 2018 (2018 IEEE CPMT Symposium Japan, ICSJ 2018) 159 - 162 2019.01

ISSN 9781538654422

© 2018 IEEE. We have proposed the Mosquito method to fabricate polymer optical waveguides with graded-index (GI) circular cores and demonstrated their excellent optical property. We have employed glass substrate which has a smooth surface for the waveguide fabrication using the Mosquito method. However, waveguides integrated on PCBs are expected for the on-board optical interconnection applications. The Mosquito method have a capability to directly fabricate waveguides on PCBs.In this paper, optical waveguides are fabricated on PCBs directly using FR-4 substrates which are a standard PCB. Here, the waveguide facet termination process is very important. Generally, waveguide ends are cut with the PCB using a dicing saw or polished after fabricating the waveguides separately from PCBs. In this paper, we propose a new waveguide facet termination process, which could be involved in the Mosquito method, and report the improvement of coupling efficiency to other optical components because the waveguide ends have sufficiently smooth surfaces.

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Fabrication and evaluation for polymer waveguide coupler devices using the imprint method

Nakazaki F., Ishigure T.

2018 IEEE CPMT Symposium Japan, ICSJ 2018 (2018 IEEE CPMT Symposium Japan, ICSJ 2018) 175 - 178 2019.01

ISSN 9781538654422

© 2018 IEEE. For further increase of data rate in multimode fiber (MMF) links widely deployed in datacenters, wavelength division multiplexing (WDM) transmission technology is expected to be introduced. In this paper, we propose a Y-branched polymer waveguide with graded-index core for optical coupler in the MMF WDM links. The low loss structure of the Y-branched polymer waveguide is designed applying BPM simulation, and designed waveguide structures are actually fabricated using an imprint method to confirm their applicability to a low-loss optical coupler in MMF WDM links.

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Fabrication for organic-inorganic hybrid resin based single-mode polymer optical waveguides using the imprinting method for high density optical circuit

Fujihara Y., Ishigure T.

2018 IEEE CPMT Symposium Japan, ICSJ 2018 (2018 IEEE CPMT Symposium Japan, ICSJ 2018) 125 - 126 2019.01

ISSN 9781538654422

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Fabrication for Y-branched multimode polymer optical waveguides using the Mosquito method

Nakayama T., Ishigure T.

2018 IEEE CPMT Symposium Japan, ICSJ 2018 (2018 IEEE CPMT Symposium Japan, ICSJ 2018) 155 - 158 2019.01

ISSN 9781538654422

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Graded-index polymer optical waveguide for restricted mode launch device enabling high-bandwidth, longer-reach multimode fiber link

Hatai R., Ishigure T.

2018 IEEE CPMT Symposium Japan, ICSJ 2018 (2018 IEEE CPMT Symposium Japan, ICSJ 2018) 71 - 74 2019.01

ISSN 9781538654422

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Directly inscribed multimode polymer waveguide and 3D device for high-speed and high-density optical interconnects

Xu X., Ma L., Shi Y., Ishigure T., He Z.

Optics Express (Optics Express) 27 ( 16 ) 22419 - 22428 2019

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement A 75-cm-long circular-core polymer waveguide compatible with standard 50-µm-core multimode fibers (MMFs) is designed and fabricated by using a direct inscribing method for high-speed and high-density optical interconnects. The fabricated waveguide has low loss (<0.044 dB/cm at 850 nm) and low crosstalk (<-34 dB with a core pitch of 62.5 µm) with a negligible coupling loss with the MMFs. It also exhibits a low bending loss (<0.08 dB/mm with a bending radius of 4 mm), which agrees well with calculated results. Error-free NRZ data transmission over the 75-cm-long waveguide at 25 Gb/s is demonstrated, and 4 × 25 Gb/s short wavelength division multiplexing (SWDM) is realized on a straight waveguide. Moreover, a two-layer waveguide and a 3-dimensional (3D) Y-splitter/combiner are also fabricated for 3D integration.

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Circular core single-mode 3-dimensional crossover polymer waveguides fabricated with the Mosquito method

Rasel O., Ishigure T.

Optics Express (Optics Express) 27 ( 22 ) 32465 - 32479 2019

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement We experimentally fabricate circular core 3-dimensional (3D) crossover single-mode polymer optical waveguides using a photomask free unique fabrication technique named the Mosquito method for realizing channel shuffling. The 3D crossover structure is accomplished by forming four cores (2 ch. × 2 ch.) with different heights: the last two channels cross over the first two channels with horizontal and vertical core bending. We compare the insertion losses between the fabricated 3D single-mode crossover waveguide and 3D S-bend core waveguides fabricated separately, which correspond to the lower and upper channels in the crossover waveguide. Then, we investigate the effect of the core crossover on the loss, and find that almost negligible additional loss is observed. The average insertion losses of this 6-cm long 3D crossover single-mode waveguide are 3.95 and 3.81 dB at 1310 nm, and 5.74 and 4.80 dB at 1550-nm wavelength, for the lower and upper channels, respectively. The interchannel crosstalk in this crossover waveguide is observed to be lower than −40 dB, while the 1 dB radial alignment tolerance is ± 1.7 and ± 2.1 µm at 1310 and 1550 nm, respectively. These results suggest that the fabricated circular core single-mode 3D crossover polymer waveguides could have a great impact for high-bandwidth-density on-board and inter-chip optical interconnect applications.

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Design and Fabrication of Broadband Polymer Mode (De)Multiplexer Using a Direct Inscribing Method

Xu X., Ma L., Marushima C., Ishigure T., He Z.

IEEE Photonics Journal (IEEE Photonics Journal) 10 ( 6 ) 2018.12

© 2009-2012 IEEE. We demonstrate the design and fabrication of a mode (de)multiplexer based on the tapered mode-selective coupler. The proposed device is directly inscribed in the substrate material by a needle-type liquid micro-dispenser and a three-axis robot stage using commercially available UV-curable resins. The fabricated mode (de)multiplexer has an excess loss less than 0.3 dB, a coupling ratio higher than 0.93, and an extinction ratio higher than 23 dB within a broadband of 100 nm around 1550 nm. The near field patterns of LP{11} mode at different wavelengths were successfully observed using an infrared charge-coupled-device camera. The fabrication tolerance on the spacing, core diameter deviation, and core circularity were investigated and the results imply that our fabrication process can satisfy the requirements on it. The proposed method is capable of fabricating functional devices for high-speed on-board optical interconnects.

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Direct Fabrication for Polymer Optical Waveguide in PMT Ferrule Using the Mosquito Method

Ishigure T., Masuda H., Date K., Marushima C., Enomoto T.

Proceedings - Electronic Components and Technology Conference (Proceedings - Electronic Components and Technology Conference) 2018-May 1103 - 1108 2018.08

ISSN 9781538649985

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Accurate core alignment for polymer optical waveguide in the mosquito method for high-efficient coupling

Morimoto Y., Date K., Ishigure T.

Proceedings - Electronic Components and Technology Conference (Proceedings - Electronic Components and Technology Conference) 2018-May 2444 - 2449 2018.08

ISSN 9781538649985

© 2018 IEEE. We demonstrate the importance of vertical position accuracy of formed core in the polymer optical waveguides fabricated using the Mosquito method for 3-dimensional wiring. We theoretically confirm the core vertical position deviation from the designed position is caused by the several fabrication parameters, the needle size and the needle-scanning speed. As an example of 3-dimensional wiring, we focus on the optical path conversion by 45-degree mirrors, and experimentally investigate the influence of the core vertical position on the coupling efficiency to other components via a 45-degree mirror. By forming the cores on appropriate height in the cladding, graded-index core optical waveguides exhibit a slight loss increment as low as 0.2 dB due to mirror structure, realizing the high efficient coupling via a 45-degree mirror.

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Low-Loss 3-Dimensional Shuffling Grand-Index Polymer Optical Wave-guide for Optical Printed Circuit Boards

Md. Omar Faruk Rasel, Akira Yamauchi, Takaaki Ishigure

IEICE Transactions on Electronics (電子情報通信学会) E101-c ( 7 ) 2018.07

Research paper (scientific journal), Joint Work, Accepted

Low-loss 3-dimensional shuffling graded-index polymer optical waveguides for optical printed circuit boards

Rasel O., Yamauchi A., Ishigure T.

IEICE Transactions on Electronics (IEICE Transactions on Electronics) E101C ( 7 ) 509 - 517 2018.07

ISSN 09168524

© Copyright 2018 The Institute of Electronics, Information and Communication Engineers. This paper introduces a formation method for 3- dimensional 6 ch. ×6 ch. shuffling structures with graded-index (GI) circular core in a multimode polymer optical waveguide for optical printed circuit boards (OPCBs) using a unique photomask-free fabrication technique named the Mosquito method. The interchannel pitch of the fabricated waveguides is 250 μm, where all the channels consist of both horizontal and vertical bending structures and the last 6 channels in parallel cross over the first 6 channels. We also report 3-dimensional S-shaped polymer waveguides. In the S-shaped waveguides, the first and last 6 channels with both horizontal and vertical core bending composing the above 3-dimensional shuffling waveguide are separated, in order to evaluate the effect of over-crossing on the loss. It is experimentally confirmed that there is no excess insertion loss due to the shuffling structure in the 3-D shuffling waveguide. The evaluated crosstalk of the 3-D shuffling waveguide is lower than -30 dB. The 3-D shuffling waveguide proposed in this paper will be a promising component to achieve high bandwidth density wiring for on-board optical interconnects.

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Core position alignment in polymer optical waveguides fabricated using the Mosquito method

Date K., Fukagata K., Ishigure T.

Optics Express (Optics Express) 26 ( 12 ) 15632 - 15641 2018.06

© 2018 Optical Society of America. We fabricate multimode polymer optical waveguides with circular graded-index (GI) cores which are aligned in parallel at desired positions using the Mosquito method. In the Mosquito method, three-dimensional wiring patterns can be formed with a simple process. However, the core position is likely to deviate from the designed position because of multiple fabrication factors. Hence, in this paper, the dominant parameters to influence on the core height in the cladding are investigated both theoretically and experimentally. In particular, a linear relationship between the core height and the needle-tip height is confirmed with theoretical fluid analysis. Using this relationship, we succeeded in fabricating a waveguide in which the maximum variation of the core height from the designed value is controlled to be less than 10 µm.

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Precise core alignment in fabrication of polymer optical waveguides using the mosquito method for three-dimensional optical circuits

Kumi Date, Koji, Fukagata, and Takaaki Ishigure

Proceeding of SPIE (Proceedings of SPIE - The International Society for Optical Engineering) 10535 105351Y-1 - 105351Y-8 2018.02

Research paper (international conference proceedings), Joint Work, ISSN 9781510615557

Polymer optical waveguides fabricated using the Mosquito method are expected to realize high bandwidth density 3-
dimensional (3-D) on-board wiring. In the Mosquito method, the waveguides are fabricated by dispensing a liquid core
monomer into a liquid cladding monomer using a microdispenser. Hence, for the on-board applications particularly 3-D
wiring, the core position and alignment accuracies are important to couple the waveguides with the other optical
components with high efficiency. We already succeeded in fabricating graded-index core multimode polymer optical
waveguides with low propagation loss using the Mosquito method. However, the positions of the formed cores tended to
deviate from the original design, since both the core and cladding monomers are in the liquid state during the Mosquito
process.
In this paper, we apply a fluid analysis simulation using a COMSOL Multiphysics® in order to theoretically
simulate the influence of several fabrication parameters on the core position. The calculated core height deviation from the
designed height is dependent on the needle-tip height, because the core positions are influenced by the pressure distribution
of cladding monomer caused by the monomer flow. Meanwhile, we find that the monomer wetting on the needle outer
wall also affects the core height. When the effect of monomer wetting is taken into account, the simulated core heights are
different from the results without the effect of monomer wetting and we can theoretically predict the height of the formed
core. Finally, we confirm that the core height can be controlled by adjusting the needle-tip height setting in which the
effect of the monomer flow and wetting theoretically calculated is taken into account in the Mosquito method.

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Design and Fabrication of Restricted Mode Launching Device for High-Speed Multimode Fiber Link

Ryosuke Hatai, Takaaki Ishigure

Proceeding of SPIE (Proceedings of SPIE - The International Society for Optical Engineering) 10560 105600V-1 - 105600V-7 2018.02

Research paper (international conference proceedings), Joint Work, ISSN 9781510616059

The IP traffic in datacenter has rapidly increased over the last couple of years because of the wide deployment of cloud
computing services. Hence, multimode fiber (MMF) links are already deployed in the rack-to-rack networks particularly
in large-scale datacenters to sustain the rapid growth of data traffic. In recent years, the network topology in datacenters
shifts from the legacy tree-type to fabric-type: the leaf and spine structure is requiring higher-bandwidth distant product
for the MMF links to maintain low latency. However, the modal dispersion has been a large issue to realize high bandwidth
links.To address the problem, we focus on the restricted mode launch (RML) approach, by which optical power is coupled
to limited numbers of propagating modes in MMFs. Key parameters for the RML are the numerical aperture (NA) and the
spot size on the MMF launch end: both of them should be small to reduce the modal dispersion. These are difficult to
achieve with small-size launch systems composed of microlenses. Thus, in this paper, a new compact RML device without
using microlenses is designed and fabricated: an axially tapered graded-index (GI) core polymer optical waveguide is
applied to the RML exciter.
Firstly, the launch condition for a 1000-m long OM3 fiber is investigated by calculating the effective modal
bandwidth (EMBc). To realize OM4-grade EMBc, we find that the NA and the spot size of the launching beam should be
lower than 0.118 and 33.2 m, respectively. Also, the polymer waveguides are designed to meet the above conditions. The
optimum refractive index profile of the tapered core is calculated by solving the Fick’s diffusion equation, and then using
the beam propagation method (BPM), the spot sizes and NAs from the tapered polymer waveguides are simulated. Finally,
we fabricate GI core tapered waveguides using the imprint method.

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Low-loss graded-index polymer crossed optical waveguide with high thermal resistance

Kohei Abe, Yutaro Oizumi, and Takaaki Ishigure

Optics Express (OSA) 26 ( 8 ) 4512 - 4521 2018.02

Research paper (scientific journal), Joint Work, Accepted

In this paper, crossed polymer waveguides with graded-index (GI) square cores are
fabricated using the soft-lithography method. We experimentally demonstrate that the
fabricated GI-core crossed waveguides exhibit
a much lower insertion loss than conventional
step index (SI)-core counterparts, which is almost independent of the cross angle. We also
show in this paper that the crossed waveguides fabricated applying organic-inorganic hybrid
resins show remarkably high thermal resist
ance compared to the waveguides fabricated
utilizing an acrylate resin and a dopant system we previously reported.

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Competitive Evaluation of Planar Embedded Glass and Polymer Waveguides in Data Center Environments

Richard Pitwon,, Kai Wang,Akira Yamauchi, Takaaki Ishigure,Henning Schröder,Marcel Neitz, and Mayank Singh

Applied Science (MDPI) 7 940 2017.09

Research paper (scientific journal), Joint Work, Accepted

Optical printed circuit board (OPCB) waveguide materials and fabrication methods have
advanced considerably over the past 15 years, giving rise to two classes of embedded planar graded
index waveguide based on polymer and glass. We consider the performance of these two emerging
waveguide classes in view of the anticipated deployment in data center environments of optical
transceivers based on directly modulated multimode short wavelength VCSELs against those based
on longer wavelength single-mode photonic integrated circuits. We describe the fabrication of graded
index polymer waveguides, using the Mosquito and photo-addressing methods, and graded index
glass waveguides, using ion diffusion on thin glass foils. A comparative characterization was carried
out on the waveguide classes to show a clear reciprocal dependence of the performance of different
waveguide classes on wavelength. Furthermore, the different waveguide types were connected into
an optically disaggregated data switch and storage system to evaluate and validate their suitability
for deployment in future data center environments.

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Circular core single-mode polymer optical waveguide fabricated using the Mosquito method with low loss at 1310/1550 nm

Kazuki Yasuhara, Feng Yu, and Takaaki Ishigure

Optics Express (OSA) 25 ( 8 ) 8524 - 8533 2017.03

Research paper (scientific journal), Joint Work, Accepted

We fabricate low-loss single-mode (SM) polymer optical waveguides using a
photomask-free simple technique named the Mosquito method. The insertion losses of a 5-cm
long SM polymer waveguide fabricated are 2.52 dB and 4.03 dB at 1310- and 1550-nm
wavelengths, respectively. The coupling loss between a single-mode fiber and the waveguide
is as low as 0.5 dB including the Fresnel reflection. The 0.5-dB misalignment tolerance in the
radial direction is ± 2.0
μ
m at 1550 nm. The Mosquito method is promising for fabricating
SM polymer optical waveguides compatible with silicon photonics chips.

Planar polymer and glass graded index waveguides for data center applications

Richard Pitwon, Akira Yamauchi, Lars Brusberg, Kai Wang, Takaaki Ishigure, Henning Schröder, Marcel Neitz, Alex Worrall I

Proceeding of SPIE 9753 97530I-1 - 97530I-11 2016.03

Research paper (international conference proceedings), Joint Work

Embedded optical waveguide technology for optical printed circuit boards (OPCBs) has advanced considerably over the
past decade both in terms of materials and achievable waveguide structures. Two distinct classes of planar graded index
multimode waveguide have recently emerged based on polymer and glass materials. We report on the suitability of
graded index polymer waveguides, fabricated using the Mosquito method, and graded index glass waveguides, fabricated
using ion diffusion on thin glass foils, for deployment within future data center environments as part of an optically
disaggregated architecture. To this end, we first characterize the wavelength dependent performance of different
waveguide types to assess their suitability with respect to two dominant emerging multimode transceiver classes based
on directly modulated 850 nm VCSELs and 1310 silicon photonics devices. Furthermore we connect the different
waveguide types into an optically disaggregated data storage system and characterize their performance with respect to
different common high speed data protocols used at the intra and inter rack level including 10 Gb Ethernet and Serial
Attached SCSI.

Low-loss polymer optical waveguides with graded-index perfect circular cores for on-board interconnection

Yuki Saito,Koji Fukagata, and Takaaki Ishigure

Proceeding of SPIE 9750 975005-1 - 975005-6 2016.03

Research paper (international conference proceedings), Joint Work

Using the Mosquito method, we fabricate low-loss multimode polymer optical waveguides with graded-index (GI) perfect circular cores for the applications to on-board optical interconnection. We already developed the Mosquito method utilizing a microdispenser, as a fabrication technique for GI circular core polymer waveguides. In the Mosquito method, a liquid-state core monomer is dispensed from a syringe needle into a liquid-state cladding monomer while the needle horizontally scans. Originally we used siloxane based monomers. In this paper, novel organic-inorganic hybrid materials (SUNCONNECT®) are selected to confirm the applicability of wide-range polymers to the Mosquito method. Here, a dip is observed on the upper perimeter of the obtained core cross-sections particularly when using a straight needle. Such a core-shape deformation increases the coupling loss with circular-core optical fibers. So, the flow of core and cladding monomers while dispensing the core with the needle scan is visually observed. It is confirmed that the edge of the straight needle chips off the upper perimeter of the core when the core monomer is dispensed, leading to the dip. Therefore, the straight needle is replaced for a curved one to change the dispensing direction for eliminating the dip. It is experimentally found that an almost circular core (50-μm diameter with 1.09 vertical to horizontal ratio of diameter) is formed when a curved needle is used. Finally, we successfully demonstrate a 1.73-dB lower loss in a 5-cm long waveguide compared to the one having the core with a dip.

Low-loss light coupling with graded-index core polymer optical waveguides via 45-degree mirrors

Yoshie Morimoto and Takaaki Ishigure

Optics Express (OSA) 24 ( 4 ) 3550 - 3561 2016.02

Research paper (scientific journal), Joint Work, Accepted

We experimentally investigate
the optical loss of graded-index
(GI) core polymer optical waveguides with a 45-degree mirror on their one
end fabricated using the photo-addre
ssing method. In addition, we also
theoretically analyze the loss of GI
square-core waveguides with mirrors
using a ray-trace simulation tool. Then, in the waveguide based optical link
including the optical path conversions
via 45-degree mirrors, we show that
GI waveguides realize lower total optical loss than conventional step-index
(SI) core waveguides. The lower loss in the GI waveguide link is attributed
to the tight optical confinement at the co
re center even after reflection at the
mirrors.

Index-profile design for low-loss crossed multimode waveguide for optical printed circuit board

Takaaki Ishigure, Keishiro Shitanda, and Yutaro Oizmi

Optics Express (OSA) 23 ( 17 ) 22262 - 22273 2015.08

Research paper (scientific journal), Joint Work, Accepted

We present an index profile design for remarkably low loss
multimode optical crossed waveguide.
In this paper, we theoretically
calculate the light propagation loss in crossed waveguides with step-index
(SI) and graded-index (GI) square co
res utilizing a ray tracing simulation.
In this simulation, we focus on the index exponent values for the GI profile,
which allows low crossing loss even if the number of crossing is as large as
50 or even if the crossing angle is as low as 20°. It is revealed that an index
exponent of 2.0 for the GI core strongly contributes to exhibit 35 times
lower loss (0.072 dB after 50-perpendicula
r crosses) compared to the loss of
the SI-core counterpart (2.58 dB after the same crossings). The GI cores
with a smaller index exponent exhibit better loss in crossed waveguides
with a wide range of crossing angles from 30° to 90°. Furthermore, we
discuss the effect of the refractive i
ndex profile at the intersection on the
optical loss of crossed waveguides.

Fan-in/out polymer optical waveguide for a multicore fiber fabricated using the Mosquito method

ISHIGURE TAKAAKI,SUGNUMA DAISUKE

Optics Express 23 ( 2 ) 1585 - 1593 2015.01

Research paper (scientific journal), Joint Work

超高速光通信の実現に向けて，1本の光ファイバ内に複数コアを集積したマルチコアファイバの研究が盛んに行われている．本論文は，この各コアに信号光を入射する/各コアからの信号光を取り出す技術の一つして，ポリマー製のFan-in/out導波路を独自の方法で作製し，その光学特性について明らかにしたものである．作製法として用いたモスキート法は，3次元のコア配線を可能にし，これまでのポリマー光導波路では困難であったFan-in/out構造が得られることを示した．

Analysis of interchannel crosstalk in multimode parallel optical waveguides using the beam propagation method

Takuya Kudo and Takaaki Ishigure

Optics Express 22 ( 8 ) 9675 - 9686 2014.04

Research paper (scientific journal), Joint Work, Accepted

We theoretically analyze the origin of inter-channel crosstalk in
densely aligned multimode parallel optical waveguides for on-board
interconnects using the Beam Propagation Method. In this paper, we
demonstrate that the inter-channel crosstalk due to mode coupling is very
low in graded-index (GI) circular-core waveguides because the propagation
constants of the propagating modes are discrete. Additionally, it is also
found that the waveguides with GI-type circular cores is sensitive to the
optical confinement in the cladding: low-power cladding modes largely
decrease the mode conversion.

Accurate interchannel pitch control in graded-index circular-core polymer parallel optical waveguide using the Mosquito method

Ryota Kinoshita, Daisuke Suganuma, and Takaaki Ishigure

Optics Express 22 ( 7 ) 8426 - 8437 2014.04

Research paper (scientific journal), Joint Work, Accepted

We successfully fabricate polymer optical waveguides with graded-index (GI) circular cores whose diameter and interchannel pitch are accurately controlled using the Mosquito method: GI-core waveguides with 250-, 125- and 62.5-μm pitches are successfully obtained. The Mosquito method utilizing a microdispenser is a very simple technique for fabricating GI-circular-core polymer optical waveguides. The accurately controlled pitch is confirmed by a high connectivity with a commercially available multimode fiber (MMF) ribbon with a 125-μm pitch. Furthermore, by inserting the waveguide between two 12-channel MMF ribbons, we experimentally demonstrate 11.3 Gbps × 12 Ch. parallel signal transmission through a GI-core waveguide with a 125-μm pitch for the first time to the best of our knowledge.

Polymer Optical Waveguides With GI and W-Shaped Cores for High-Bandwidth-Density On-Board Interconnects

Ryota Kinosita, Kimio Moriya, Koji Choki, and Takaaki Ishigure

Journal of Lightwave Technology (IEEE/OSA) 31 ( 24 ) 4004-4015 2013.12

Research paper (scientific journal), Joint Work

We fabricate polynorbornene-based graded-index
(GI) core polymer optical waveguides using the photoaddressing method, and demonstrate that the GI-core polymer waveguides are capable of realizing high-bandwidth-density on-board optical interconnects. Because of the tight optical confinement effect of the parabolic refractive index profile, the fabricated GI-core polymer waveguides exhibit superior optical properties compared to stepindex (SI) core polymer waveguides: low propagation loss, low connection loss with GI multimode fiber (MMF) with wide misalignment tolerance, and low interchannel crosstalk even under a small pitch size are experimentally confirmed. Furthermore, interchannel crosstalk due to multicore operation is experimentally evaluated, and a method to estimate the interchannel crosstalk in multimode polymer parallel optical waveguides under multicore
operation is proposed for the first time, to the best of our knowledge. The photoaddressing method capable of fabricating even low-loss GI-core polymer waveguide circuits will pave the way for realizing low-cost and high-bandwidth-density optical printed circuit boards.

Photonic bandgap Bragg fiber sensors for bending/displacement detection

Hang Qu, Tiberius Brastaviceanu, Francois Bergeron, Jonathan Olesik, Ivan Pavlov, Takaaki Ishigure, and Maksim Skorobogatiy

Applied Optics (OSA) 52 ( 25 ) 6344-6349 2013.09

Research paper (scientific journal), Joint Work, Accepted

We demonstrate an amplitude-based bending/displacement sensor that uses a plastic photonic bandgap
Bragg fiber with one end coated with a silver layer. The reflection intensity of the Bragg fiber is
characterized in response to different displacements (or bending curvatures). We note that the Bragg
reflector of the fiber acts as an efficient mode stripper for the wavelengths near the edge of the fiber
bandgap, which makes the sensor extremely sensitive to bending or displacements at these wavelengths.
Besides, by comparison of the Bragg fiber sensor to a sensor based on a standard multimode fiber
with similar outer diameter and length, we find that the Bragg fiber sensor is more sensitive to bending
due to the presence of a mode stripper in the form of a multilayer reflector. Experimental results show
that the minimum detection limit of the Bragg fiber sensor can be as small as 3 μm for displacement
sensing.

Analysis of Connection Loss for a GI Waveguide Based Optical Link Using the Finite Difference Beam Propagation Method

HSU HSIANG-HAN, ISHIGURE TAKAAKI, NAKAGAWA SHIGERU

Journal of Lightwave Technology (IEEE/OSA) 31 ( 12 ) 2036-2042 2013.06

Research paper (scientific journal), Joint Work, Accepted

The connection loss which occurs when light transfers
from one medium to another attracts additional attention in highspeed and low-power optical links. In this paper, we not only experimentally apply graded index polymer optical waveguide (GIPOW) in the optical link, but also theoretically address some key parameters which largely influence on the connection loss. The experimental setup of this optical link is composed of a VCSEL module, a GI polymer optical waveguide for the transmitter side(WGTx), a GI multimode fiber (GI-MMF), a GI polymer optical waveguide for the receiver side (WGRx), and a detector. We assume that WGTx is launched by a single mode fiber and then measure the connection losses at the interface between any two components. The results show the connection loss between the GI-MMF and the WGRx is approximately 0.4 dB higher than that of the WGTxto theGI-MMF. For the theoreticalmodeling, we start from the fundamental scalar wave equation, and apply the finite difference beam propagation method (FD-BPM) to simulate the behavior of light inside the waveguide. Furthermore, Fresnel reflection between two media and the scattering effect within polymer optical waveguides are also taken into account. The simulated results show a similar trend to the measured values. Finally, we conclude that the scattering effect could be one of the key issues of GI-POW for maintaining low connection losses with other waveguides
and fibers.

Fabrication of a Graded-Index Circular-Core Polymer Parallel Optical Waveguide Using a Microdispenser for a High-Density Optical Printed Circuit Board

SOMA KAZUTOMO 　ISHIGURE TAKAAKI

IEEE Selected Topics in Quantum Electronics (IEEE) 19 ( 2 ) 3600310 2013.04

Research paper (scientific journal), Joint Work, Accepted

A simple fabrication method for multimode polymer optical waveguides with graded-index (GI) circular cores is introduced for use in optical printed circuit boards (O-PCBs). The new method, named “Mosquito method,” utilizes a microdispenser to dispense a viscous monomer directly onto the substrates. By optimizing the dispensing conditions, 12-channel parallel waveguides with circular GI-cores (core diameter of 40 μm) are successfully fabricated using the Mosquito method. The advantages of GI-core waveguides for O-PCB applications are discussed by comparing the optical characteristics of the fabricated waveguides with those of conventional step-index (SI) square-core polymer waveguides, and even with those of silica-based GI multimode fibers (MMFs), as an ideal case. To the best of our knowledge, this is the first comparison of SI- and GI-core multimode polymer waveguides that are composed of the same polymer materials and that have similar core and pitch sizes. We experimentally demonstrate that the GI circular-core polymer waveguides fabricated by the Mosquito method have sufficiently low propagation loss (0.033 dB/cm at 850 nm), low connection loss with GI-MMFs, and low interchannel crosstalk. We observe approximately −50 dB of interchannel crosstalk in the 250-μm pitch GI-core waveguide fabricated, which is almost 10 dB lower than in the SI counterpart. Furthermore, sufficiently low crosstalk is maintained in a half-pitch GI-core waveguide fabricated by the Mosquito method.

Carbon nanotube/polymer composite coated tapered fiber for four wave mixing based wavelength conversion

Bo Xu, Mika Omura, Masato Takiguchi, Amos Martinez, Takaaki Ishigure, Shinji Yamashita, and Takahiro Kuga

Optics Express (OSA) 21 ( 3 ) 3651-3657 2013.02

Research paper (scientific journal), Joint Work, Accepted

Brillouin Gain Spectrum Characteriza-tion in Perfluorinated Graded-Index Polymer Optical Fiber with 62.5-μm Core Diameter

MIZUNO YOSUKE, ISHIGURE TAKAAKI，NAKAMURA KENTARO

IEEE Photon. Technol. Lett., (IEEE) 23 ( 24 ) 1863-1865 2011.11

Research paper (scientific journal), Joint Work, Accepted

We characterize the Brillouin gain spectra (BGS) in perfluorinated graded-index polymer optical fibers (PFGI-POFs) with 62.5-μm core diameter. First, we show that the Stokes power is extremely high compared to that of a standard PFGI-POF with 120-μm core, and discuss the Brillouin threshold power. Then, we demonstrate that the PFGI-POF length has little influence on the BGS when the length is longer than 50 m. We also predict that, at 1.55-μm wavelength, it is difficult to reduce the Brillouin threshold power of PFGI-POFs below that of long silica single-mode fibers even if their core diameter is sufficiently reduced to satisfy the single-mode condition. Finally, we confirm the Brillouin linewidth narrowing effect.

Fabrication and inter-channel crosstalk analysis of polymer optical waveguides with W-shaped index profile for high-density optical interconnections

HSU HSIANG-HAN, HIROBE YUSUKE, ISHIGURE TAKAAKI

Optics Express (Optical Society (OSA)) 19 ( 15 ) 14018-14030 2011.07

Research paper (scientific journal), Joint Work, Accepted

For applications in high-density and high-speed optical interconnections, we propose to utilize polymer parallel optical waveguides (PPOWs) with so-called W-shaped refractive index profile in the core area. A W-shaped index profile is composed of a parabolic index distribution surrounded by a narrow index valley, followed by a cladding with a uniform refractive index. We expect that W-shaped index profiles contribute to decreasing the inter-channel crosstalk due to mode conversion in the waveguides. In this paper, we investigate how much the index difference of the index valley improves the crosstalk value. First, we fabricate polymer waveguides with various index profiles by changing the composition of the copolymer for cladding. We show the results that a 1-m long W-shaped profile PPOW has not only low propagation loss (0.027 dB/cm), but an inter-channel crosstalk (~-40 dB) lower than those of graded index (GI) core PPOW we previously fabricated. Next, we theoretically analyze the propagation loss and inter-channel crosstalk in polymer waveguides with different index profiles by means of a ray tracing model in which the light scattering effect is included. The calculation results indicate that the index valley surrounding each core works properly for preventing the power coupling from the cladding modes to the propagation modes, and consequently, very low inter-channel crosstalk is realized with W-shaped index profiles.

Observation of stimulated Brillouin scattering in polymer optical fiber with pump-probe technique

MIZUNO YOSUKE，KISHI MASATO， HOTATE KAZUO,　ISHIGURE TAKAAKI NAKAMURA KENTARO

Optics Letters (Optical Society （OSA)) 36 ( 12 ) 2378-2380 2011.06

Research paper (scientific journal), Joint Work

Stimulated Brillouin scattering (SBS) in a perfluorinated graded-index polymer optical fiber (POF) with 120 μm
core diameter was experimentally observed for the first time, to the best of our knowledge, at 1:55 μm wavelength
with the pump–probe technique. Compared to spontaneous Brillouin scattering previously reported, the Brillouin
gain spectrum (BGS) was detected with an extremely high signal-to-noise ratio, even with a short POF (1m) and
scrambled polarization state. We also investigated the BGS dependences on probe power and temperature, which
indicate that SBS in a POF measured with this technique can be utilized to develop high-accuracy temperature
sensing systems.

GI-core polymer parallel optical waveguide with high-loss, carbon-black-doped cladding for extra low inter-channel crosstalk

UNO HISASHI　/ISHIGURE TAKAAKI

Optics Express (Optical Society (OSA)) 19 ( 11 ) 10931-10939 2011.05

Research paper (scientific journal), Joint Work, Accepted

Graded-index (GI) polymer parallel optical waveguides with high-absorption, carbon-black-doped cladding are fabricated using the preform method in order to reduce the inter-channel crosstalk. The waveguides exhibit a lower inter-channel crosstalk (<-69.3dB) than optically-transparent-clad waveguides (~-33.7 dB) and maintain low propagation loss (0.029dB/cm). We characterize the waveguides with different concentration of carbon black in order to confirm the required concentration (required absorption loss) for keeping the inter-channel crosstalk low enough. In addition, carbon-black-doped waveguides are fabricated directly on a substrate by means of a soft-lithography method. Crosstalk is sufficiently decreased despite the high scattering loss of the core material, while insertion loss is not increased. Furthermore, we fabricate a waveguide with a high-scattering-loss cladding to confirm the origin of low crosstalk in carbon-black-doped waveguides. We confirm that high scattering loss of cladding is not necessarily as effective for crosstalk reduction as high absorption loss of cladding.

Polymer optical waveguide with multiple graded-index cores for on-board interconnects fabricated using soft-lithography

ISHIGURE TAKAAKI　/　NITTA YOSUKE

Optics Express (Optical Society (OSA)) 18 ( 13 ) 14191-14201 2010.06

Research paper (scientific journal), Joint Work

We successfully fabricate a polymer optical waveguide with
multiple graded-index (GI) cores directly on a substrate utilizing the softlithography method. A UV-curable polymer (TPIR-202) supplied from Tokyo Ohka Kogyo Co., Ltd. is used, and the GI cores are formed during the curing process of the core region, which is similar to the preform process we previously reported. We experimentally confirm that near
parabolic refractive index profiles are formed in the parallel cores (more than 50 channels) with 40 μm x 40 μm size at 250-μm pitch. Although the loss is still as high as 0.1 ~0.3 dB/cm at 850 nm, which is mainly due to scattering loss inherent to the polymer matrix, the scattering loss attributed to the waveguide’s structural irregularity could be sufficiently reduced by a graded refractive index profile. For comparison, we fabricate step-index (SI)-core waveguides with the same materials by means of the same process. Then, we evaluate the inter-channel crosstalk in the SI- and GI-core waveguides under almost the same conditions. It is noteworthy that remarkable crosstalk reduction (5 dB and beyond) is confirmed in the GI core waveguides, since the propagating modes in GI-cores are tightly confined near the core center and less optical power is found near the core-cladding boundary. This significant improvement in the inter-channel
crosstalk allows the GI-core waveguides to be utilized for extra high-density on-board optical interconnections.

High-density channel alignment of graded index core polymer optical waveguide and its crosstalk analysis with ray tracing method

HSU HSIANG-HAN, ISHIGURE TAKAAKI

Optics Express (Optical Society (OSA)) 18 ( 13 ) 13368-13378 2010.06

Research paper (scientific journal), Joint Work

We fabricate graded index (GI) multi-channel polymer optical
waveguides comprised of poly methyl methacrylate(PMMA)-poly benzyl methacrylate copolymer for the purpose of achieving high thermal stability
in the GI profiles. The waveguides obtained show slightly higher propagation loss (0.033 dB/cm at 850 nm) than doped PMMA based GI core polymer waveguides we have reported, due to the excess scattering loss inherent to the mixture of copolymer and homo-polymer in the core area. In this paper, we focus on the influence of the excess scattering loss on mode conversion and inter-channel crosstalk. We simulate the behavior of light propagating inside the core with and without the scattering effect.
Using the simulation, the excess loss experimentally observed in the copolymer-core waveguide is successfully reproduced, and then, we find that the excess scattering loss of 0.008 dB/cm could increase the inter channel crosstalk from −30 dB to −23 dB which agrees with the
experimentally observed value. Although the simulation of the inter channel crosstalk was performed only on our GI-core polymer optical waveguides, it is capable of modeling the conventional SI rectangular-core waveguides. Some amount of excess scattering is generally observed in the conventional SI-core waveguides, and thus, the application of this simulation to SI-core waveguides allows a feasible design for high-density alignment of the waveguides.

Carbon Nanotube-Doped Polymer Optical Fiber

UCHIDA　SHO,　AMOZ MALTINEZ,　SONG　YON　DON, ISHIGURE TAKAAKI,　YAMASHITA SHINJI

Optics Letters (Optical Society (OSA)) 34 ( 20 ) 3077-3079 2009.10

Research paper (scientific journal), Joint Work, Accepted

Polymer parallel optical waveguide with graded-index rectangular cores and its dispersion analysis

KOSUGI　TOMOYA, ISHIGURE TAKAAKI

Optics　Express (Optical Society (OSA)) 17 ( 18 ) 15959-15968 2009.08

Research paper (scientific journal), Joint Work, Accepted

High-Density 2 X 4 Channel Polymer Optical Waveguide with Graded-Index Circular Cores

YUSUKE TAKEYOSHI, ISHIGURE TAKAAKI

Journal of Lightwave Technology (IEEE/OSA) 27 ( 14 ) 2852-2861 2009

Research paper (scientific journal), Joint Work, Accepted

Fabrication of Carbon nanotube poly-methyl-methacrylate composites for nonlinear photonic devices

ISHIGURE TAKAAKI

Optics Express (Optical Society of America) 16 ( 15 ) 11337-11343 2008.07

Research paper (scientific journal), Joint Work, Accepted

Polymer Parallel Waveguide with Circular W-shaped Index Profile Cores

TAKEYOSHI YUSUKE / ISHIGURE TAKAAKI

IEEE Photonics Technology Letters (IEEE) 19 ( 22 ) 1795-1797 2007.11

Research paper (scientific journal), Joint Work, Accepted

Densely Aligned Multichannel Polymer Waveguide With Low Inter-Channel Crosstalk

TAKEYOSHI YUSUKE　/　ISHIGURE TAKAAKI

IEEE Photonics Technology Letters (IEEE) 19 ( 19 ) 1430-1432 2007.10

Research paper (scientific journal), Joint Work

屈折率分布型円形コアを有するポリマー並列導波路は，従来の均一屈折率コア型導波路に比べて，屈折率分布によりコア部への光の閉じ込め効果が強く，従って，より高密度に並列配線を施しても，チャネル間のクロストークが十分に低減できることを実験的に明らかにした．また，コア部への光の入射位置ずれに対しても許容が大きく，低クロストークを保てることを確認した．

Polymer waveguide with 4-channel graded-index circular cores for parallel optical interconnects

ISHIGURE TAKAAKI　/ 　TAKEYOSHI YUSUKE

Optics Express (Optical Society of America) 15 ( 9 ) 5843-5850 2007.04

Research paper (scientific journal), Joint Work, Accepted

ハイエンドルータやサーバ，HPCなどの筐体内光インターコネクションを実現する低損失で高密度・高速伝送ポリマー並列光導波路を初めて提案した論文である．従来型のポリマー導波路は半導体プロセスによる作製法をベースとしているため，コア部が矩形で均一屈折率コアを有するが，本提案の導波路は，円形で屈折率分布型コアを有する．このため，従来導波路に比べ，十分な低損失性と広帯域性，さらに，強いコア部への光閉じ込め効果を有することを示した．

Propagating Mode Analysis and Design of Waveguide Parameters of GI POF for Very Short-Reach Network Use

ISHIGURE TAKAAKI

IEEE Photonics Technology Letters (IEEE) 17 ( 1 ) 2005.01

Research paper (scientific journal), Joint Work, Accepted

High-Bandwidth Plastic Optical Fiber with W-Refractive Index Pro-file

ISHIGURE TAKAAKI

IEEE Photonics Tech-nology Letters (IEEE) 16 ( 9 ) 2081-2083 2004.09

Research paper (scientific journal), Joint Work, Accepted

A Large-Core, High-Bandwidth Graded-Index Plastic Optical Fiber with High Mechanical Flexibility that Enables an Easy Installation of Optical Data Links: 2

ISHIGURE TAKAAKI

Journal of Applied Polymer Science 91 ( 1 ) 410-416 2004.01

Research paper (scientific journal), Joint Work, Accepted

A Large-Core, High-Bandwidth Graded-Index Plastic Optical Fiber with High Mechanical Flexibility that Enables an Easy Installation of Optical Data Links: 1

ISHIGURE TAKAAKI

Journal of Applied Polymer Science 91 ( 1 ) 404-409 2004.01

Research paper (scientific journal), Joint Work, Accepted

High-Bandwidth Graded-Index Plastic Optical Fiber Enabling Power Penalty-Free Gigabit Data Transmission

ISHIGURE TAKAAKI

IEEE Journal of Lightwave Technology 21 ( 11 ) 2923-2930 2003.11

Research paper (scientific journal), Joint Work

Data transmission over polymer op-tical fibers

Monroy TI, Boom HPAV, Koonen AMJ, Khoe GD, 渡邊勇仁, 小池康博,石榑崇明(/)-#HR

Optical Fiber Technology 9 ( 3 ) 159-171 2003.07

Research paper (scientific journal), Joint Work, Accepted

Graded-Index Polymer Optical Fiber with High Temperature and High Humidity Stability

石榑崇明、佐藤真隆、近藤篤志、月森康之、小池康博

IEEE Journal of Lightwave Technology 20 ( 10 ) 1815-1825 2002.10

Research paper (scientific journal), Joint Work

Accurate Refractive Index Profiling in Graded-Index Plastic Optical Fiber Exceeding Gigabit Transmission　Rates

石榑崇明、田中奨、小林英嗣、小池康博

IEEE J. Lightwave Technol. 20 ( 8 ) 1449-1456 2002.08

Joint Work

PMMA系GI型POFの屈折率分布形状を最適に制御するための新規作製法を提案し、実際に試作した。得られたGI型POFは、150mで3GHzを超える広い帯域を有しており、この結果は理論的にWKB法を用いて計算されたシミュレーション結果と非常によい一致を示した。石英系のマルチモードファイバーにおいても制御が困難とされてきた理想屈折率分布を形成することに始めて成功した報告である。

High-Bandwidth Graded-Index Polymer Optical Fiber with High Temperature Stability

石榑崇明、佐藤真隆、近藤篤志、小池康博

IEEE Journal of Lightwave Technology 20 ( 8 ) 1443-1448 2002.08

Research paper (scientific journal), Joint Work

ポリマー光ファイバーが拓くブロードバンドネットワーク

石榑　崇明、小池　康博

高分子学会誌 2002.06

Joint Work

高速POFによるブロードバンドネットワーク

小池　康博、石榑　崇明

JEITA Review 　 vol.3 ( no.1 ) 28- 2002.01

Joint Work

広帯域プラスチック光ファイバー

小池　康博、佐藤　真隆、石榑　崇明

応用物理学会誌　（2001）第70巻 ( 第11号 ) 1287-1293 2001.10

Joint Work

世界最高速を可能にするGI型ポリマー光ファイバ　　

小池康博, 石榑崇明, 大津信弘　

レーザー研究(496) 第29巻 ( 8号( ) 2001.08

Joint Work

プラスチック光ファイバの新展開

石榑崇明、小池康博　

電子情報通信学会誌 2001

Joint Work

Thermally Stable High-Bandwidth Graded-Index Polymer Optical Fiber

佐藤真隆、平井美季、石榑崇明、小池康博　

IEEE J. Lightwave Technol., 18(12) 2139-2145 2000.12

Joint Work

プラスチック光ファイバ最近の話題

石榑崇明、小池康博　

光産業技術振興協会オプトニューズ, 5　 38-42 2000.09

Joint Work

Novel Photonics Polymers in High-Speed Telecommunication

Mole. Crystl. and Liq. Crystl.,353 451-469 (2000) 2000.08

Joint Work

High-Speed Plastic Optical Fibers

佐藤真隆、石榑崇明、小池康博　

Science and Technology in Japan, 19 (74) 15-27 2000.07

Joint Work

Thermally Stable High　Bandwidth Graded　Index Polymer Optical Fiber

佐藤真隆、石榑崇明、小池康博　

IEEE J. Lightwave Technol., 18 (7) 952-958 2000.07

Joint Work

Which Is More Serious Factor to the Bandwidth of GI POF: Differential Mode Attenuation or Mode Coupling?

石榑崇明、叶真理子、小池康博　

IEEE J. Lightwave 18 (7) 　959-966 2000.07

Joint Work

世界最高速ポリマー光ファイバー

小池康博、石榑崇明　

高分子学会誌, 49 (7) 431-434 2000.07

Joint Work

高速ポリマー光ファイバー（POF）の現状と将来展望

石榑崇明、小池康博　

信学技報、LQE99-135 31-36 2000.03

Joint Work

Optimum index profile of the perfluorinated polymer based GI polymer optical fiber and its dispersion properties

石榑崇明、小池康博、James W. Fleming

IEEE J. Lightwave Technol., 18 (2) 　178-184 2000.02

Joint Work

光通信と情報家電の動向

小池康博、石榑崇明　

機械振興　通巻-2000 ( 380号 ) 65-71 2000.01

Joint Work

屈折率傾斜ポリマー光ファイバ

小池康博、石榑崇明　　

マテリアル　インテグレーション　第12巻　 ( 第10号 ) 33-38 1999.09

Joint Work

マルチメディアのためのフォトニクスポリマー

小池康博、多加谷明広、石榑崇明

プラスチック成形加工学会誌 Vol.11 ( No.8　 ) 680-684 1999.08

Joint Work

Bandwidth and Transmission Distance Achieved by POF

小池康博、石榑崇明　

IEICE Trans. Electron., E82-C (8) 　 1287-1295 1999.08

Joint Work

Graded-Index Polymer Optical Fiber with High Thermal Stability of Bandwidth

石榑崇明、佐藤真隆、二瓶栄輔、小池康博　

Jpn. J. of Appl. Phys. 37 3986 - 3991 1998.07

Joint Work

High-Speed Photonics Polymer and Its Application

小池康博、石榑崇明、佐藤真隆、二瓶栄輔　低損失、

Pure and Appl. Opt., 7, 201-210 1998.03

Joint Work

Gigabit Transmission by Perdeuterated PMMA Graded Index Polymer Optical Fiber

石榑崇明、二瓶栄輔、小池康博　

繊維学会誌（投稿論文） 12 Vol.53 520-525 1997.12

Joint Work

Formation of the Refractive Index Profile in the Graded Index Polymer Optical Fiber for Gigabit Data Transmission

石榑崇明、佐藤真隆、高梨紀、二瓶栄輔、丹生隆之、山崎俊太郎、小池康博　

IEEE J. Lightwave Technol.,15, (11) 2095-2100 1997.11

Joint Work

Present Prospect of Graded　Index Plastic Optical Fiber in Telecommunication

二瓶栄輔、石榑崇明、谷尾宣久、小池康博　

IEICE Trans. Electron., 　E80-C (1) 117-122 1997.01

Joint Work

High-Bandwidth Graded-index Polymer Optical Fiber for Near Infra-Red Use

二瓶栄輔、石榑崇明、小池康博　

Appl. Opt., 35　(36) 7085-7090 1996.12

Joint Work

Optimum Refractive Index Profile of the Graded-Index Polymer Optical Fiber, toward Gigabit Data Links

石榑崇明、二瓶栄輔、小池康博　

Appl. Opt., 35 (12) 2048-2053 1996.04

Joint Work

Optimization of the Refractive-index Distribution of High-Bandwidth GI Polymer Optical Fiber based on Both Modal and Material Dispersions

石榑崇明、二瓶栄輔、小池康博　

Polymer J., 28 (3) 272-275 1996.03

Joint Work

High-Bandwidth, High-Numerical Aperture Graded-Index Polymer Optical Fiber

石榑崇明、堀部晃啓、二瓶栄輔、小池康博

IEEE J. Lightwave Technol.,13(8) 1686-1691 1995.08

Joint Work

High-Bandwidth Graded-Index Polymer Optical Fiber

小池康博、石榑崇明、二瓶栄輔　

IEEE J. Lightwave 　Technol., 13 (7) 1475-1489 1995.07

Joint Work

Large-Core, High-Bandwidth Polymer Optical Fiber for Near　Infrared Use

石榑崇明、二瓶栄輔、小池康博、

IEEE Photon. Technol. Lett.,7(4) 403-405 1995.04

Joint Work

2.5Gb/s 100m Data Transmission Using Graded-Index Polymer Optical Fiber and High-Speed Laser 　Diode at 650nm wavelength

石榑崇明、二瓶栄輔、小林建一、山崎俊太郎、小池康博　

Electron. Lett., 31(6) 467-468 1995.03

Joint Work

Graded-Index Polymer Optical Fiber for High Speed Data Communication

石榑崇明、二瓶栄輔、小池康博　

Appl. Opt., 33 　(19), 4261-4266 1994.07

Joint Work

High-Bandwidth and High Numerical Aperture Graded-Index Polymer Optical Fiber

石榑崇明、堀部晃啓、二瓶栄輔、小池康博、

Electron. Lett., 30(14) 1169-1170 1994.07

Joint Work

high-Speed Multimedia Network by Polymer Optical Fiber

小池康博、石榑崇明、二瓶栄輔

Technical Digest of 4th Iketani Conference 1993.05

Joint Work

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