Analysis of Si3N4 waveguides for on-chip gas sensing by optical absorption within the mid-infrared region between 2.7 and 3.4 µm

Abstract

We theoretically investigated the use of a Si3N4 on SiO2 waveguide as an optical interaction part with sensed molecules for multi-gas wideband on-chip spectroscopic sensing. From the analysis, we show that a simple strip Si3N4 waveguide can be employed to achieve acceptable values of performance in term of detection limit, compactness, polarization, and fabrication tolerance for the detection of water vapor (H2O), carbon dioxide (CO2), Nitrous oxide (N2O), Ammonia (NH3), Ethylene (C2H4), and Methane (CH4) gas molecules, with a wideband operation between 2.7 and 3.4 µm optical wavelength. The results show that a simple Si3N4 waveguide structure could attain competitive performance required for generic on-chip spectroscopic sensing for environmental and agricultural usage.