Second-harmonic output at 4.6–5.5 μm of the order of 6 mW with a 0.12% external conversion efficiency has been obtained by pumping a AgGaSe<sub>2</sub> crystal with a low-power cw CO<sub>2</sub> laser. The surface damage threshold of AgGaSe<sub>2</sub> for cw radiation was found to be inside the limit of 33–45 kW/cm<sup>2</sup> in the 9.2–10.8-μm wavelength region. Another important limitation of the pump power connected with a thermal lensing effect in crystal was determined experimentally. A comparison was made of AgGaSe<sub>2</sub> and ZnGeP<sub>2</sub> crystals as materials suitable for the efficient generation of the second harmonic of cw CO<sub>2</sub> laser radiation.
© 1997 Optical Society of America
S. Ya. Tochitsky, V. O. Petukhov, V. A. Gorobets, V. V. Churakov, and V. N. Jakimovich, "Efficient continuous-wave frequency doubling of a tunable CO2 laser in AgGaSe2," Appl. Opt. 36, 1882-1888 (1997)