CO2 laser frequency doubling in a new nonlinear AgGaxIn1–xSe2 crystal

The optical properties of a new promising nonlinear mixed AgGa_xIn_1–xSe₂ crystal were investigated. Its absorption coefficients and refractive indices were determined at wavelengths 0.8 — 19 μm. For the first time the coefficients of the Sellmeier dispersion equations were determined for different indium contents. The corresponding phase-matching diagrams for second-harmonic generation and an optical parametric oscillator pumped by a Er³⁺:YAG laser were calculated and plotted. An experiment on the generation of the second harmonic of a TEA CO₂ laser and a Q-switched laser was carried out and a frequency doubling efficiency of 10.9% was obtained. AgGaSe₂ and ZnGeP₂ crystals were also investigated for comparison.