Design of an on-chip integrated multi-channel comb filter based on the Bragg grating structure

We designed a multi-channel comb filter generation scheme with nearly consistent channel numbers and free spectral range (FSR) in standard 220-nm-thick silicon-on-insulator (SOI) technology. This scheme relies on the formation of optical microcavities using Bragg grating structures, which serve as reflectors. By precisely designing the optical path length of the microcavity, we can generate optical filters with a specific number of channels. Using this scheme, we developed and tested three devices to implement two-channel, three-channel, and four-channel comb filters, with FSRs of approximately 5.5 nm, 4 nm, and 3.3 nm, respectively. As an application, this three-channel filter can be used to implement a temperature sensor with a high temperature sensitivity of about 53 pm/K. The proposed multi-channel comb filter provides a novel, to the best of our knowledge, scheme to utilize Bragg gratings, offering a new perspective for future densely integrated silicon photonics.