チーバくんのぬいぐるみ / Chi-ba-kun plush toy

Keisuke Kawahara (川原 啓輔)

Assistant Professor （助教）

Department of Electrical and Electronic Engineering, School of Engineering, Institute of Science Tokyo

東京科学大学 工学院 電気電子系

CV (researchmap)

Research Topics

My research focuses on electronic–photonic co-design for integrated circuits. My work combines transistor-level design of high-speed analog circuits, photonic device and circuit design, and digital signal processing. By bridging electronics and photonics and harnessing the strengths of both, I aim to create hardware that enables next-generation communications and computing. I also develop device models and simulation environments to expand these design possibilities.

Optical Transceivers for Data Centers

Co-design of optical modulators and their electronic drivers enables high-speed, low-power optical transceivers. The research spans silicon, thin-film lithium niobate, and EML (EA-DFB) devices, drawing on slow light and traveling-wave electrodes. View more

Broadband D/A and A/D Conversion and Sampling

The goal is to generate and measure broadband signals beyond the speed limits of electronic devices. The approach combines photonic devices and electronic circuits for multiplexing and frequency conversion. View more

Electronic Circuits on Silicon Photonics

Electronic circuits built in silicon photonics processes provide local measurement and control for photonic circuits. This reduces external wiring and supports larger-scale photonic integration. View more

AI-Friendly Electronic–Photonic Co-Design Platform

This work develops an EDA platform for co-design that makes photonic and electronic device models and simulation environments readily usable by AI tools. The goal is to streamline and improve the design of integrated electronic–photonic circuits. View more

Selected Publications

My research has been published in leading journals from IEEE, Optica, and Springer Nature, and presented at major international conferences including OFC, ECOC, OECC, ISCAS, and RWW. I am the first and corresponding author of all papers listed below.

Silicon photonic crystal slow-light optical modulator

High-Speed, Low-Voltage, Low-Bit-Energy Silicon Photonic Crystal Slow-Light Modulator With Impedance-Engineered Distributed Electrodes

K. Kawahara, T. Tsuchizawa, N. Yamamoto, Y. Maegami, K. Yamada, S. Hara, and T. Baba

Optica, vol. 11, no. 9, pp. 1212–1219, Sep. 2024. PDF

Related presentation: OFC 2024Slide

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Chip micrograph of the fabricated inductor-less CMOS active balun

A 0.0058-mm² Inductor-Less CMOS Active Balun With Gain and Phase Errors Within −0.1 ± 0.2 dB and −0.18 ± 1.17° From DC to 8 GHz

K. Kawahara, Y. Umeda, K. Takano, and S. Hara

IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 70, no. 6, pp. 2317–2330, Jun. 2023. PDF

Related presentation: IEEE MWSCAS 2021Slide

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Chip micrograph of the image-rejection analog multiplexer

Bandwidth Tripler: Broadband Signal Generation With an Image-Rejection Analog Multiplexer for Fiber Optic Transmitters

K. Kawahara, J. Sawada, T. Kamo, Y. Umeda, K. Takano, and S. Hara

IEEE Transactions on Microwave Theory and Techniques, vol. 71, no. 1, pp. 22–34, Jan. 2023. PDF

Related presentation: IEEE RWS 2022Slide

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For a complete record of my work, please see Google Scholar or researchmap.