Tunable Optical Parametric Oscillator Based on MgO:PPLN and HgGa₂S₄ Crystals Pumped by an Nd:YAG Laser with Increased Energy Characteristics

We report the development of a combined optical parametric oscillator based on a fan-out MgO:PPLN crystal and a HgGa₂S₄ crystal, providing smooth wavelength tuning in the spectral range from 2.5 to 10.8 μm. A transversely pumped Nd:YAG laser with a pulse energy of ∼4 mJ and a spatial beam distribution described by a second-order Gaussian function along the x axis and a fourth-order Gaussian function along the y axis is used as a pump source. A maximum achievable radiation energy of the optical parametric oscillator is at a level of 360 μJ for a wavelength of 3.3 μm, 130 μJ for a wavelength of 4.73 μm, and 110 μJ for a wavelength of 7.40 μm. The developed radiation source is used to record absorption spectra of gas mixtures of methane, propane and nitrogen dioxide.