Mid-Infrared Trace Gas Sensor Technology Based on Intracavity Quartz-Enhanced Photoacoustic Spectroscopy

Abstract

The application of compact inexpensive trace gas sensor technology to a mid-infrared nitric oxide (NO) detectoion using intracavity quartz-enhanced photoacoustic spectroscopy (I-QEPAS) is reported. A minimum detection limit of 4.8 ppbv within a 30 ms integration time was demonstrated by using a room-temperature, continuous-wave, distributed-feedback quantum cascade laser (QCL) emitting at 5.263 µm (1900.08 cm−1) and a new compact design of a high-finesse bow-tie optical cavity with an integrated resonant quartz tuning fork (QTF). The optimum configuration of the bow-tie cavity was simulated using custom software. Measurements were performed with a wavelength modulation scheme (WM) using a 2f detection procedure.

Review of Recent Advances in QEPAS-Based Trace Gas Sensing

“…An intra-cavity QEPAS (I-QEPAS) sensor was first reported by Vincenzo Spagnolo [55] and was further developed for sensitive carbon dioxide (CO 2 ) and nitric oxide (NO) detection [56][57][58]. Due to the output coupling loss, the laser power intensity in the intra-cavity is much higher than outside.…”

Recent advances in quartz enhanced photoacoustic sensing

“…The improvement in terms of sensitivity with respect to conventional QEPAS setup (operating under the same conditions of molecular linewidth, pressure and laser output power) is equal to the power enhancement factor occurring in the optical resonator ($240 in Refs. 54 and 55) Recently, novel compact bow-tie cavities capable to reach power enhancement factors over 300 have been realized, 56,57 promising even further improvements in detection sensitivity. Since to-date a bare QTF was used in I-QEPAS based sensors.…”

Cavity-enhanced photoacoustic sensor based on a whispering-gallery-mode diode laser

“…A 1σ detection limit of 109 ppbV was achieved with a 1 s averaging time. An alternative method of achieving high power is to combine PAS with cavity-enhanced absorption spectroscopy (CEAS) (Hippler et al, 2010;Kachanov et al, 2013;Wojtas et al, 2017). In 2015, Patimisco et al (2015) proposed an intra-cavity QEPAS (I-QEPAS) sensor for CO 2 detection at 4.33 µm (Patimisco et al, 2015).…”