Ultracompact bandwidth-tunable filter based on subwavelength grating-assisted contra-directional couplers

Abstract

An ultracompact, bandwidth-tunable filter has been demonstrated using a silicon-on-insulator (SOI) wafer. The device is based on cascaded grating-assisted contra-directional couplers (GACDCs). It also involves the use of a subwavelength grating (SWG) structure. By heating one of the heaters on GACDCs, a bandwidth tunability of ~6 nm is achieved. Owing to the benefit of having a large coupling coefficient between SWG and strip waveguides, the length of the coupling region is only 100 μm. Moreover, the combination of the curved SWG and the tapered strip waveguides effectively suppresses the sidelobes. The filter possesses features of simultaneous wavelength tuning with no free spectral range (FSR) limitation. A maximum bandwidth of 10 nm was experimentally measured with a high out-of-band contrast of 25 dB. Similarly, the minimum bandwidth recorded is 4 nm with an out-of-band contrast of 15 dB.

Graphical abstract

Keywords

silicon-based devices / tunable filter / subwavelength / grating waveguide / grating-assisted contra-directional coupler (GACDC)

References

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Acknowledgements

This work was supported in part by the National Key R&D Program of China (No. 2019YFB2203101), in part by the National Natural Science Foundation of China (Grant Nos. 61805137 and 61835008), in part by the Natural Science Foundation of Shanghai, China (No. 19ZR1475400), Shanghai Sailing Program (No. 18YF1411900), and Open Project Program of Wuhan National Laboratory for Optoelectronics (No. 2018WNLOKF012).

The authors acknowledge the support of the device fabrication by the Center for Advanced Electronic Materials and Devices of Shanghai Jiao Tong University, China.

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