Sub-ppb-level CH<sub>4</sub> detection by exploiting a low-noise differential photoacoustic resonator with a room-temperature interband cascade laser
Huadan Zheng, Yihua Liu, Haoyang Lin, Ruifeng Kan, Pietro Patimisco, Angelo Sampaolo, Marilena Giglio, Wenguo Zhu, Jianhui Yu, Frank K. Tittel, Vincenzo Spagnolo, Zhe Chen
Abstract
An ultra-highly sensitive and robust CH 4 sensor is reported based on a 3.3 µm interband cascade laser (ICL) and a low-noise differential photoacoustic (PAS) cell. The ICL emission wavelength targeted a fundamental absorption line of CH 4 at 2988.795 cm −1 with an intensity of 1.08 × 10 −19 cm/molecule. The double-pass and differential design of the PAS cell effectively enhanced the PAS signal amplitude and decreased its background noise. The wavelength modulation depth, operating pressure and V-T relaxation promotion were optimized to maximize the sensor detection limit. With an integration time of 90 s, a detection limit of 0.6 ppb was achieved. No additional water or air laser cooling were required and thereby allowing the realization of a compact and robust CH 4 sensor.