Real-time ultrasensitive detection of ammonia gas using a compact CRDS spectrometer

Abstract

Trace-level ammonia gas in air was analyzed using a fiber-based compact cavity ring-down spectrometer (CRDS). For the compact spectrometer, a 20 cm linear cavity with two high reflectivity (>99.999%) mirrors was employed. The laser frequency was locked to the cavity resonance by using frequency shifted (160 MHz) optical feedback. For NH3 detection, a strong absorption band at 1513.98 nm with an absorption cross section of 3.3 middot 10-21 cm/molecule was used. As a result, a detection sensitivity of similar to 0.1 ppb (3-Sigma) was achieved for NH3 within 10 s.(c) 2023 Optica Publishing Group