Details of a Researcher - Ishigure, Takaaki

Papers - Ishigure, Takaaki

Division display 21 - 40 of about 162 ／ All the affair displays >>

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

Access to Document (DOI)

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

Access to Document (DOI)

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.

Access to Document (DOI)

Polymer Optical Waveguide Coupler with Vertically Bent Cores

Itaru N., Kohmu N., Ishigure T.

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

Access to Document (DOI)

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

Access to Document (DOI)

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

Access to Document (DOI)

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.

Access to Document (DOI)

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.

Access to Document (DOI)

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.

Access to Document (DOI)

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.

Access to Document (DOI)

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.

Access to Document (DOI)

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.

Access to Document (DOI)

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.

Access to Document (DOI)

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

Access to Document (DOI)

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.

Access to Document (DOI)

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

Access to Document (DOI)

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.

Access to Document (DOI)

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

Access to Document (DOI)

　 Previous page - Next page 　