# Versatile photoacoustic spectrometer based on a mid-infrared pulsed optical parametric oscillator

## TL;DR

This paper presents a versatile mid-infrared photoacoustic spectrometer utilizing a pulsed optical parametric oscillator, capable of real-time trace gas detection with high sensitivity and spectral resolution, suitable for environmental and breath analysis.

## Contribution

The study introduces a novel MIR OPO-based photoacoustic spectrometer with broad wavelength tunability and high detection sensitivity for multiple trace gases.

## Key findings

- Achieved detection limit of 8 ppbV for methane.
- Demonstrated real-time measurement capability with 300 ml/min flow rate.
- Spectral measurements closely match HITRAN database data.

## Abstract

We demonstrate the usefulness of a nanosecond pulsed single-mode mid-infrared (MIR) optical parametric oscillator (OPO) for Photoacoustic (PA) spectroscopic measurements. The maximum wavelength ranges for the signal and idler are 1.4 um to 1.7 um and 2.8 um to 4.6 um, respectively, and with a MIR output power of up to 500 mW. Making the OPO useful for different spectroscopic PA trace-gas measurements targeting the major market opportunity of environmental monitoring and breath gas analysis. We perform spectroscopic measurements of methane (CH4) nitrogen dioxide (NO2) and ammonia (NH3) in the 2.8 um to 3.7 um wavelength region. The measurements were conducted with a constant flow rate of 300 ml/min, thus demonstrating the suitability of the gas sensor for real time trace gas measurements. The acquired spectra are compared with data from the Hitran database and good agreement is found. Demonstrating a resolution bandwidth of 1.5 1/cm. An Allan deviation analysis shows that the detection limit for methane at optimum integration time for the PA sensor is 8 ppbV (nmol/mol) at 105 seconds of integration time.