Mid-infrared intracavity quartz-enhanced photoacoustic spectroscopy with pptv – Level sensitivity using a T-shaped custom tuning fork

Abstract

Resonant optical power buildup inside a high finesse cavity is exploited to boost the sensitivity in quartz-enhanced photoacoustic spectroscopy (QEPAS) for CO, N2O and H2O detection, operating at a wavelength of 4.59 µm. A quartz tuning fork with T-shaped prongs optimized for QEPAS has been employed. Exploiting the high signal-to-noise ratio attainable with this tuning fork together with an optical power amplification of ~100 enabled by efficient optical feedback locking, limits of detection (3σ, 10 s integration) of 260 ppt and 750 ppt for CO and N2O have been reached.

Keywords

• QEPAS
• Cavity enhanced spectroscopy
• Trace gas sensing
• Costum quartz tuning fork
• Quantum cascade laser