Compact optical parametric oscillator based tunable mid-IR difference frequency laser spectrometer for intracavity photoacoustic trace gas sensing

摘要

We have developed a nanosecond pulsed optical parametric oscillator (OPO) based difference frequency generation (DFG) photoacoustic (PA) spectrometer for sensitive trace gas monitoring. By mixing the residual fundamental of the Nd:YAG pump laser with the idler output of the commercial OPO (1.41.85 μm) in bulk LiNbO{sub}3 the wavelength range from 2.5-4.5 μm is covered with considerable pulse energies. This very broad tuning range combined with the yet narrow emission linewidth of ≤0.3 cm{sup}(-1) accounts for the selectivity of the system. Absorption spectra of multi-component mixtures consisting of up to seven gases at concentration levels in the lower ppm-range and with strongly interfering spectral characteristics have been recorded and analyzed.