EXPERIMENTAL INVESTIGATION OF SINGLE AND TWIN AGGASE2 CRYSTALS FOR CW 10.2-MU-M SHG

Two twin AgGaSe2 crystals (l(c)=20 mm) cut for the second-harmonic generation (SHG) of 10.2 mu m radiation have been submitted to up to 1.3 W single-mode continuous-wave (CW) output of a CO2 laser focused to a decreasing beam radius w(0). For a power density exceeding 1.6 kW/cm(2), corresponding to a focusing parameter l=l(c)/z(R) far under the theoretical optimum one, the second-harmonic (SH) generated power starts to saturate due to thermal effects. The study of the conversion efficiency versus the focusing parameter for the walkoff-compensated twin device reveals that this two-crystal device is more efficient than would be a single crystal of length 2l(c), despite the small walkoff angle in this material.