Abstract

Manipulating the coupling coefficient at subwavelength scales provides an additional degree of freedom in designing integrated Bragg gratings. We demonstrate asymmetric contradirectional couplers (contra-DCs) using sidewall-corrugated subwavelength grating (SWG) waveguides for broadband add–drop Bragg filters. We show that a SWG can effectively increase the overlap of coupled modes and thus the photonic band gap. The measured spectra show good agreement with the prediction of photonic band structure simulations. A record bandwidth of 4.07 THz (33.4 nm) has been achieved experimentally. A four-port Bragg resonating filter made of a phase-shifted Bragg grating SWG contra-DC is also demonstrated for narrow-band (near 100 GHz) filtering. All these devices are achieved on the 220-nm silicon-on-insulator platform with a compact length of less than 150 μm. These large stopband filters may find important applications such as band splitting, reconfigurable channel band switching, bandwidth-tunable filtering, and dispersion engineering.

© 2018 Optical Society of America

Broadband flat-top SOI add–drop filters using apodized sub-wavelength grating contradirectional couplers

Han Yun, Mustafa Hammood, Stephen Lin, Lukas Chrostowski, and Nicolas A. F. Jaeger
Opt. Lett. 44(20) 4929-4932 (2019)

Spectral engineering of subwavelength-grating-based contradirectional couplers

Behnam Naghdi and Lawrence R. Chen
Opt. Express 25(21) 25310-25317 (2017)

FSR-free add–drop filter based on silicon grating-assisted contradirectional couplers

Huiye Qiu, Guomin Jiang, Ting Hu, Haifeng Shao, Ping Yu, Jianyi Yang, and Xiaoqing Jiang
Opt. Lett. 38(1) 1-3 (2013)

Polymer/silica hybrid integration add-drop filter based on grating-assisted contradirectional coupler

Liang Tian, Fei Wang, Yuanda Wu, Yunji Yi, Xiaoqiang Sun, and Daming Zhang
Opt. Lett. 43(10) 2348-2351 (2018)

Silicon photonic contradirectional couplers using subwavelength grating waveguides

Behnam Naghdi and Lawrence R. Chen
Opt. Express 24(20) 23429-23438 (2016)