Possibilities and experimental investigation of parametric frequency converters with LiInSe/sub 2/, AgGaGeS/sub 4/, HgGa/sub 2/S/sub 4/ and Hg/sub 0.65/Cd/sub 0.35/Ga/sub 2/S/sub 4/ crystals

Second harmonic generation of 9 /spl mu/m emission band of CO/sub 2/ laser is for the first time realized with a number of new nonlinear crystals: biaxial LiInSe/sub 2/, AgGaGeS/sub 4/ (that is solid solution AgGaS/sub 2/:GeS/sub 2/ or Ag/sub x/Ga/sub x/Ge/sub (1-x)/S/sub 2/, or AgGaGe/sub x/S/sub 2(1+x)/ at x=0.5) and uniaxial HgGa/sub 2/S/sub 4/, Cd/sub 0.35/Hg/sub 0.65/Ga/sub 2/S/sub 4/ (solid solution HgGa/sub 2/S/sub 4/:CdGa/sub 2/S/sub 4/ with mixing ratio x=0.35). For LiInSe/sub 2/ and AgGaGeS/sub 4/ it is first type of frequency conversion realized at some time or other. The main feature of these crystals is a wide range transparency from 0.4-0.6 to 12.5-16.2 /spl mu/m. Their damage thresholds for 30 ns TEA CO/sub 2/ laser pulses at 9.55 /spl mu/m is determined as 1.7 to 2.3 times higher than for popular middle IR crystals such as ZnGeP/sub 2/ or AgGaSe/sub 2/. Parameters of second harmonic generation were determined correctly in comparison with ZnGeP/sub 2/ crystals at 33 ns pump pulses and intensities that are about 28.5% (40 MW/cm/sup 2/) of damage thresholds of ZnGeP/sub 2/. As high as 7% external peak power efficiencies (4.7% in energy) is typical for orange and yellow phases of 3.1 mm HgGa/sub 2/S/sub 4/ crystal such pumping that is only 13% of its damage threshold. Efficiencies as high as 0.45% and 0.3% are realized in 2.1 mm AgGaGeS/sub 4/ crystal at pump intensities-that is only 11% of the damage threshold. Phase-matching angles, spectral dependence of second harmonic generation efficiencies, and angular and spectral phase-matching widths are investigated in detail.