Theoretical and experimental investigation of chalcogenide suspended waveguide gas sensor

To address the issues of low ratio of evanescent field (& gamma;) and high reflectivity between waveguide cross-section and gas for the mid-infrared waveguide sensors, we propose a chalcogenide (ChG) suspended waveguide with Ge28Sb12Se60 as the core layer and silica (SiO2) as the buffer layer. The SiO2 beneath the waveguide core ridge structure is removed to create suspended structure. The waveguide sensing performance is obtained using a 10% methane (CH4) sample. The fabricated waveguide exhibits a & gamma; of 112%, which is a 10% improvement compared to a free-space optical sensor with the same optical path length. The good agreement between the theoretical and experimental results of & gamma; confirms the reliability of our theoretical investigation approach. The influences of fabrication error, environmental temperature, and pressure on sensing performances are discussed. This work provides theoretical guidance for designing waveguide structures with large & gamma;, contributing to the further enhancement of on-chip sensor performance.