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

摘要

Second harmonic generation of 9 μm 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}xGa{sub}xGe{sub}(1-x)S{sub}2, or AgGaGe{sub}xS{sub}(2(1+x)) at x=0.5) and uniaxial HgGa{sub}2S{sub}4, Cd{sub}0.35Hg{sub}0.65Ga{sub}2S{sub}4 (solid solution HgGa{sub}2S{sub}4:CdGa{sub}2S{sub}4 with mixing ratio x=0.35). For LiInSe{sub}2 and AgGaGeS{sub}4 it is first type of frequency conversion realized some time or other. Main feature of this crystals is wide range transparency from 0.4-0.6 to 12.5-16.2 μm. Their damage thresholds for 30 ns TEA CO{sub}2 laser pulses at 9.55 μm 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}2S{sub}4 crystal at such pump 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 damage threshold. Its were determined phase-matching angles, spectral dependence of second harmonic generation efficiencies, so as angular and spectral phase-matching widths that are investigated in details.