Frequency conversion of CO laser radiation was experimentally studied in ZnGeP(2) and GaSe nonlinear crystals. To enhance conversion efficiency, we applied a CO laser system "master oscillator power amplifier" with concurrent mode locking and Q switching. The laser system emitted ∼1-μs train of ns pulses. Internal efficiency of frequency doubling reached 37% in ZnGeP(2) crystal and 5% in GaSe crystal. Two-stage frequency conversion (including second-harmonic and difference-frequency generation) in ZnGeP(2) crystal under optical pumping by a selective two-spectral line CO laser was studied.
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