Details of a Researcher - Ishigure, Takaaki

Papers - Ishigure, Takaaki

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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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