Frequency conversion of mid-IR lasers into the long-wavelength domain of 12-20 µm with AgGaSe2, BaGa2GeSe6 and PbIn6Te10 nonlinear crystals.

Difference frequency generation under mixing of repetitively-pulsed CO- and CO2-laser radiation in AgGaSe2, BaGa2GeSe6 and PbIn6Te10 nonlinear crystals was studied. Efficiency and refractive indices were examined for this frequency conversion into the long-wave domain of ∼12-20 µm in the mid-IR. The highest frequency conversion efficiency of 10-4 was obtained for a relatively new PbIn6Te10 crystal, which is an order of magnitude higher than previous results.

Verification of an integral figure of merit for mid-IR nonlinear crystals.

The examination and verification of a simple integral figure of merit for nonlinear crystals, taking into account different crystal properties, was studied. The examination was carried out on the basis of experimental data on the broadband sum frequency generation of CO laser radiation in ZnGeP2, BaGa2GeSe6, AgGaSe2, GaSe, and PbIn6Te10 mid-IR nonlinear crystals. Taking into account spectral and angular phase-matching bandwidths, the figure of merit provides the best agreement with the experiment and can be applied for qualitative, and even quantitative, comparison of the nonlinear crystals.

Sum frequency generation of multi-line slab radio frequency discharge carbon monoxide laser system with intracavity nonlinear BaGa2GeSe6 crystal.

A compact repetitively pulsed broadband carbon monoxide (CO) laser system with intracavity frequency conversion, for which a nonlinear crystal was also used as an output coupler, was launched for the first time, to the best of our knowledge. The laser system simultaneously operated in two spectral ranges: CO laser fundamental band (4.9-6.0 µm) and its sum frequencies band (2.45-2.95 µm). Different designs of the laser cavity were considered. Peak powers of the fundamental and sum frequencies laser pulses were up to 2 kW and 10 W, respectively.