  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.
