Combined optical parametric oscillator with continuous tuning of radiation wavelength in the spectral range 2.5 – 10.8 μm

A combined optical parametric oscillator (OPO) with continuous tuning of the radiation wavelength in the spectral range 2.5 – 10.8 μm, optically pumped with the radiation from a Q-switched Nd : YLF laser (1.053 μm), is developed and tested. The oscillation is provided by an OPO1 based on a MgO : PPLN 'fanout' structure in the spectral region 2.5 – 4.5 μm and by an OPO2 based on HgGa₂S₄ nonlinear crystals in the spectral region 4.18 – 10.8 μm, respectively. The angles of phase matching are measured for the HgGa₂S₄ crystals in the spectral range 4.18 – 10.8 μm for the type II conversion (eo-e), which virtually coincide with the calculated ones. The experimental absorption spectra of a gas mixture in the range 2.5 – 10.8 μm obtained using a gas-filled sealed-off photoacoustic cell are presented.