Inverse design of refractory mid-wave infrared narrowband thermal emitters for optical gas sensing

Spectrally selective thermal emitters with narrow bandwidth and high temperature stability are of great interest for a variety of applications in the mid-infrared region, ranging from thermal imaging and infrared sensing to high-temperature thermophotovoltaics. Herein, a lithography-free, wafer-scale, aperiodic mid-wave infrared narrowband thermal emitter is proposed and optimized by inverse design. Experimental results show that a fabricated prototype emitter exhibits a narrowband thermal emissivity peak of 90% around 3.82 mm with high temperature stability up to 1,200 K. Numerical simulation analyses are employed to corroborate the experimental results. Infrared formaldehyde-gas-sensing tests are further conducted to verify the versatile functionality of the proposed emitters, and an order-of-magnitude improvement in relative sensitivity is obtained compared with that of a conventional blackbody emitter. The proposed approach can be implemented in refractory infrared light sources, allowing applications in thermal imaging and optical gas sensing.