Cavity-enhanced high-speed mid-infrared trace gas measurement system using a narrowband-filtered InAs detector and a quantum interband cascade LED

A compact mid-infrared (MIR) cavity-enhanced measurement system for trace gas analysis of methane was developed based on a quantum interband cascade light-emitting diode (IC-LED) emitting at a center wavelength of 3.3 µm. The setup integrates a low-noise indium arsenide (InAs) detector equipped with an integrated narrowband optical filter featuring a full width at half maximum (FWHM) of 35 nm, along with a customdesigned amplifier circuit capable of detecting modulation frequencies up to 30 kHz. A short coupling distance between the IC-LED and a cavity mirror was implemented to enhance optical feedback and maximize signal throughput, while maintaining a compact and mechanically stable geometry optimized for high-speed operation. The IC-LED was operated in pulsed overdrive mode at 30 kHz to achieve sixteen times higher peak optical power compared to continuous-wave (CW) operation, while compensating for increased thermal load. The integrated narrowband detector filter enables precise spectral selection around the methane absorption peak at 3.315 µm, improving measurement selectivity and signal-to-noise ratio. The short light-source-to-mirror coupling distance was experimentally optimized to maximize coupling efficiency and minimize optical losses. Initial results demonstrate stable, low-noise MIR signal acquisition and efficient modulation response up to 30 kHz, confirming the suitability of the presented architecture for fast gas detection and spectroscopic sensing. The compact and energy-efficient design provides a scalable foundation for portable MIR sensing platforms. In environmental applications, such systems can support emission control by enabling localized detection of unintended methane releases.