Multi-Objective Inverse Design of a Dual-Narrowband Thermal Emitter for Optical Gas Sensing

Spectrally selective narrowband thermal emitters with high-temperature stability are critical infrared sources for advanced gas sensing. However, conventional Tamm-plasmon narrowband thermal emitters are commonly implemented as distributed Bragg reflectors on thin metal layers, which can restrict spectral tunability and complementary metal-oxide-semiconductor (CMOS) compatibility. Here, we propose a cost-effective, CMOS-compatible, lithography-free, wafer-scale aperiodic dual-narrowband thermal emitter. Optimized via a multi-objective inverse design framework, the emitter consists of an aperiodic Si/SiO₂ dielectric multilayer deposited on a TiN refractory conductive ceramic film. Experimental results demonstrate that the fabricated sample exhibits two selective emission peaks at 3.26 and 6.30 μm, matching the characteristic absorption bands of CH₄ and NO₂, respectively. In addition, the emitter maintains its dual-narrowband spectral response after heating to 693 K. In practical gas-sensing tests, the dual-narrowband emitter achieved 12.2- and 13.5-fold improvements in relative sensitivity for CH₄ and NO₂ detection, respectively, compared with a conventional broadband blackbody source. This work provides a scalable refractory infrared source for spectrally selective optical gas sensing.