Widely Tunable Automatic System for Multiple Gas Detection

Multiple gas detection is an appropriate decision for a lot of applications such as atmospheric and environmental monitoring, oil and gas exploration, industrial process control and chemical reactions, security and biomedicine. Laser photoacoustic spectroscopy is universal method for local gas analysis due to its fast response, high sensitivity and overall selectivity. The widely tunable automatic system for gas analysis based on combined optical parametric oscillators (OPOs) is demonstrated in this work. It can be tuned from 2.5 $\mu$ m to 10.8 $\mu$m. The full width at half maximum is $\sim 5.5 \pm 0.5$ cm$^{-1}$ from 2.5 to $4.5 {\mu} \mathrm{m}$ and $\sim 2 \pm 0.5$ cm$^{-1}$ from 4.5 to $10.8 {\mu} \mathrm{m}$. Using the software on the computer, the controller performs all the necessary actions for pumping, analyzing and removing a gas sample in the measuring complex. The experimental absorption spectra of a gas mixture obtained using a gas-filled sealed-off photoacoustic cell are presented. All measurements using HgGa$_{2} S_{4}$ crystals were carried out at half of the longitudinal resonance of the acoustic resonator, which led to decrease in the average power and sensitivity. In the future, it is planned to install an amplifier stage to increase the average power of the OPO radiation in $4.5- 10.8 \mu \mathrm{m}$.