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. 2020 Oct 31;14(3):374–380. doi: 10.1007/s12200-020-1056-5

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

Kangnian Wang 1, Yuan Wang 1, Xuhan Guo 1,✉, Yong Zhang 1, An He 1, Yikai Su 1
PMCID: PMC9743839  PMID: 36637729

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.

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

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.

Footnotes

Kangnian Wang received the B.S. degree of Applied Physics from Nanjing University of Posts and Telecommunications, China. In September 2017, he was admitted as a postgraduate in Shanghai Jiao Tong University, China and then he joined State Key Laboratory of Advanced Optical Communication Systems and Networks for relative research.

Yuan Wang received the B.S. degree from School of Electronic Information, Wuhan University, China. In September 2018, he was admitted as a doctoral student in Shanghai Jiao Tong University, China, and then he joined State Key Laboratory of Advanced Optical Communication Systems and Networks for relative research.

Xuhan Guo received the Ph.D. degree in Photonics from Department of Engineering, University of Cambridge, UK in 2014. He worked at University of Cambridge, UK as a Research Associate and he joined Shanghai Jiao Tong University, China as an Associate Professor in 2017. His research interests include silicon photonics, hybrid silicon laser and neuromorphic photonics.

Yong Zhang received the Ph.D. degree from Huazhong University of Science and Technology, China in 2015. He joined Shanghai Jiao Tong University, China as a Research Faculty Member in July 2015. His research interests include silicon photonics devices and circuit, microcavity devices, E-beam, lithography and ICP etching process.

An He received the B.S. degree in Applied Physics from Suzhou University of Science and Technology, China and M.S. degree from Wenzhou University, China. In September 2018, he was admitted as a doctoral student in Shanghai Jiao Tong University, China, and then he joined State Key Laboratory of Advanced Optical Communication Systems and Networks for relative research.

Yikai Su received the Ph.D. degree in Electronic Engineering from Northwestern University, Evanston, IL, USA in 2001. He worked at Crawford Hill Laboratory of Bell Laboratories and he joined Shanghai Jiao Tong University as a Full Professor in 2004. His research areas cover silicon photonic devices for information transmission and switching.

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