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High-performance grating couplers by inverse design for perfectly vertical coupling.pdf (676.58 kB)

High-performance grating couplers by inverse design for perfectly vertical coupling

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posted on 2023-03-03, 14:06 authored by Mingshan Zhao, Mingxiang Yang, YUNJIE YAN, Zhenlin Wu, Geert Morthier
In the application of free-space optical (FSO) communication, grating couplers (GCs) are the key components, enabling the coupling of the vertically incident optical beam to optical waveguides. This paper presents the design and experimental characterization of apodized grating couplers for perfectly-vertical coupling to 220 nm thick silicon-on-insulator (SOI) waveguides in the C-band. We also designed and characterized uniform grating couplers to demonstrate the superior performance of apodized grating couplers. We used a gradient-based inverse design method to optimize apodized grating couplers. The design and measurement results show that apodized grating couplers have a 3dB lower coupling loss than uniform grating couplers. We fabricated focusing apodized grating couplers by electron beam lithography with a 70 nm shallow etch and a minimum feature size of 100 nm, which is compatible with CMOS technology. They achieved an excellent coupling loss of 5.86 dB for perfectly vertical coupling.

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Funder Name

China Scholarship Council

Preprint ID

103064

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