We report the experimental results on the temperature-dependent phase-matching properties of BaGa2GeS6 for second-harmonic generation (SHG) and sum-frequency generation (SFG) of Nd:YAG laser-pumped KTiOPO4 (KTP) and HgGa2S4 (HGS) optical parametric oscillators (OPOs) and a CO2 laser in the 0.7674-10.5910 μm range. The experimental values for type-2 90° phase-matching SHG wavelengths in the short and long wavelength branches were measured to be λ1 = 2.0376 and 7.6740 μm, respectively. By using a BaGa2GeS6 crystal cut at θ = 48.1˚ and Φ = 0˚, we measured the type-1 and type-2 phase-matching angles for SHG and SFG of a Nd:YAG laser-pumped KTP OPO at λ = 3.1092 μm and HGS OPO at λ = 7.6740 μm as well as those for SHG and SFG of a waveguide CO2 laser. In addition, we derived the Sellmeier equations that provide a good reproduction of the experimental results for the phase-matching data. The temperature phase-matching bandwidths (FWHM) were also obtained in eight different phase-matching conditions by using the measured temperature variation of the pump wavelengths, the measured temperature dependence of the phase-matching angles (Δθext/ΔT) from 20℃ to 120℃ and the angular acceptance (Δθext‧l) calculated with our Sellmeier equations. Moreover, the temperature phase-matching bandwidth (FWHM) for type-2 90˚ phase-matching SHG was determined to be ΔT‧l = 12.2 ℃‧cm from the measured value of dλ1/dT = +0.3 nm/℃ and the calculated spectral bandwidth (Δλ1‧l). From these experimental results and the dn/dT measured at five wavelengths, we derived a thermo-optic dispersion formula valid in the 0.7674 − 10.5910 μm spectral range.
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