Silicon Photonics Wavelength Selective Switch With Unlimited Free Spectral Range

We propose a novel silicon photonics wavelength selective switch (WSS) with sidewall-corrugated contra-directional couplers (C-DCs), which has an unlimited free spectral range and is suitable for broadband operation. Fabricated 2 x 2 1-ch and 2-ch WSSs demonstrate the expected operation with channel wavelengths of 1532 and 1553 nm, a 3-dB bandwidth of similar to 3 nm, a flattop spectral shape, and an outband extinction ratio larger than 30 dB over a wavelength range wider than C-band. We discuss a limiting factor for the lower inband extinction of similar to 15 dB, which is a leakage to the bar port in the Mach-Zehnder (MZ) switch. Matching the center wavelength of each MZ switch to the Bragg wavelength of the corresponding C-DCs will improve the inband extinction ratio to be larger than 30 dB.