An HGS Optical Parametric Oscillator Tunable in the 4.75–9.07-μm Wavelength Range

An optical circuit is designed for the ring cavity of an optical parametric oscillator (OPO) based on two series-mounted active elements—mercury thiogallate crystals (HgGa2S4) with the radiation tunable in the near- and mid-IR ranges (4.75–9.07 μm). The dependences of the radiation idler wavelength on the phase-matching angle and of the distribution of the IR OPO output radiation intensity on the idler wavelength are derived. The possibility of narrowing the spectral width of the output radiation by introducing a dispersing element (Fabry–Perot etalon) into the cavity is considered.