Quartz Enhanced Photoacoustic Sensors for Trace Gas Detection in the IR and THz Spectral Range

Abstract

Quartz-enhanced photo-acoustic spectroscopy (QEPAS) is one of the most robust and sensitive trace-gas detection techniques, which in the mid-IR range offers the advantage of high sensitivity, compactness and fast time-response. One of the main features of the photoacoustic techniques is that no optical detection is required. Thus, the use of the QEPAS technique in THz range would allow to avoid the use of low-noise but expensive, bulky and cryogenic bolometers. The results obtained in the development of QEPAS sensors for trace gas detection of several chemical species, employing mid-IR and THz laser sources will be reviewed. Normalized noise equivalent absorption coefficients (NNEA) down to 10−10 cm−1 W/Hz½ and part per trillion concentration detection ranges have been attained.