Laser induced thermoelastic contributions from windows to signal background in a photoacoustic cell

Abstract

The existence of a signal baseline due to a variety of reasons in a photoacoustic (PA) gas measurement system is a common phenomenon. One major component is the absorption of optical windows in an enclosed PA cell. This work explores the relation between the background signal and the thermoelastic effect inside the windows by modelling the pressure and elastic wave field by means of a Green-function based method. The influence of laser incidence location, angle and radius is discussed based on a rigorous three-dimensional solid-to-fluid coupling model. The effects were theoretically demonstrated culminating in the determination of best (minimum background signal) performance using a collimated and expanded incident laser beam. The results were also validated through experiments.

Detectors for gas‐phase photoacoustic spectroscopy: A review

“…Compact and sensitive photoacoustic sensors based on different acoustic detectors have been demonstrated to be effective in numerous applications. 106 The capacitive microphone is widely used for acoustic signal acquisition of the various types of resonator due to its mature technology and low price. However, its electronic nature and structure constitutes an obstacle for the development of miniaturized and high sensitive sensors.…”

“…This article reviewed three different kinds of acoustic detectors used in PAS gas sensing including capacitive microphones, QTFs, and optical microphones. Compact and sensitive photoacoustic sensors based on different acoustic detectors have been demonstrated to be effective in numerous applications 106 . The capacitive microphone is widely used for acoustic signal acquisition of the various types of resonator due to its mature technology and low price.…”

Doubly resonant sub-ppt photoacoustic gas detection with eight decades dynamic range

“…4 (a) to (e). Note that the background signal is caused by unwanted absorption at the optical windows and resonator mirrors [31] . This background signal is not subtracted from the PAS-1f signal shown in Fig.…”

Wavelength-modulated photoacoustic spectroscopic instrumentation system for multiple greenhouse gas detection and in-field application in the Qinling mountainous region of China

“…Several photoacoustic systems addressing the detection of greenhouse gases have been reported with limits down to 65 pptv for CH 4 [10] , 10 ppb for carbon dioxide and 1.5 ppb for CO [16] . However, most of those reports used expensive high-power lasers or bulky laboratory systems and detection was performed under laboratory measurement conditions [17] , [18] , [19] , [20] , [21] .…”