Theoretical research of chalcogenide pedestal waveguide gas sensor

A rectangular waveguide with a small external confinement factor (γ) limits the gas sensing performance. The fabrication process of a suspended waveguide with large γ is complex. Pedestal waveguide can be fabricated by wet etching on the basis of a rectangular waveguide, which makes full use of the target analyte area under the core layer and increases γ. The TM mode chalcogenide pedestal waveguide was optimized to obtain a large γ. The γ of the optimized TM mode pedestal waveguide is 55.7% and the limit of detection of methane (CH4) for a 1 cm‐long waveguide is 1.67%. The fabrication tolerance of the pedestal waveguide was analyzed. The pedestal radius error has a great influence on sensing performance. This work provides a method for the design and performance analysis of a pedestal waveguide sensor.