Theoretical research of chalcogenide waveguide CH4 sensor based on lift‐off method

Chalcogenide (ChG) waveguide gas sensor with good application prospect at mid‐infrared band can be fabricated by the lift‐off method with a simple process. However, the inclined sidewalls of the core layer caused by lift‐off are unavoidable. The TE and TM mode ChG rectangular waveguides were optimized and the influence of inclined angle on the sensing performance was studied. The performance of TE mode ChG waveguide is more affected by the fabrication error of the inclined angle. The relative variation of the external confinement factor and limit of detection of the TM mode waveguide are 10 and 23 times smaller than that of the TE mode waveguide. This work provides guidance for the design, fabrication, and application of the ChG waveguide gas sensors fabricated by the lift‐off method.