Design and Simulation Investigation of SiN Photonics Circuits for Wideband On-Chip Optical Gas Sensing around 2 µm Optical Wavelength.

We theoretically explore the potential of SiN on SiO waveguide platform toward a wideband spectroscopic detection around the optical wavelength of 2 μm. The design of SiN on SiO waveguide architectures consisting of a SiN slot waveguide for a wideband on-chip spectroscopic sensing around 2 μm, and a SiN multi-mode interferometer (MMI)-based coupler for light coupling from classical strip waveguide into the identified SiN slot waveguides over a wide spectral range are investigated. We found that a SiN on SiO slot waveguide structure can be designed for using as optical interaction part over a spectral range of interest, and the MMI structure can be used to enable broadband optical coupling from a strip to the slot waveguide for wideband multi-gas on-chip spectroscopic sensing. Reasons for the operating spectral range of the system are discussed.