SM2E.5.pdf CLEO:2014 © 2014 OSA Intracavity Quartz-Enhanced Photoacoustic Sensor for Mid- Infrared Trace-Gas Detection

Abstract: Quartz-enhanced photoacoustic spectroscopy (QEPAS) and cavity-ehnanced spectroscopy are merged in a novel gas sensor. Thanks to the intracavity power build up, sensitivity is increased by more than a factor 100 with respect to standard QEPAS. OCIS codes: (300.6360) Spectroscopy, laser; (140.5965) Semiconductor lasers, quantum cascade The development of cost-effective, compact optical sensors for trace chemical species in the gas phase is, for our present society, a challenge in a wide variety of applications, including climate changes, homeland security, industrial processes control, workplace surveillance, and medical diagnostics. Since the advent of lasers, the development of high-sensitivity optical sensors followed three main criteria: i) selection of optimal molecular transition in terms of absorption strength and absence of possible interfering gases; ii) long optical absorption length and/or use of buildup optical cavity; iii) efficient spectroscopic detection schemes. Quartz-enhanced photo-acoustic spectroscopy (QEPAS) is one of the most robust and sensitive trace-gas detection techniques. It is based on the use of tiny quartz tuning forks (QTF) with a resonant frequency f0 ~ 32 kHz as a transducer to detect laser absorption by a gas sample in a compact and relatively low-cost detection module [1]. Combined with quantum cascade laser (QCL) sources has demonstrated record sensitivities down to 50 part-per-trillion (ppt) concentration levels in 1 s for SF6 [2]. Very recently the possibility of high-sensitivity gas detection i