Nonlinear frequency conversion of copper vapor laser radiation

An investigation was made of nonlinear frequency conversion of copper vapor laser radiation in a KDP crystal. Powers of 600mW were obtained at the 271 nm wavelength (sum frequency) and 120 mW at 289 nm (second harmonic of the yellow line). In both cases the conversion efficiency was ~3%. Taking into account the losses of ultraviolet radiation in the selector, the efficiency was 5%. It was observed that thermal effects, known to be related to the average power level, did not cause any drop in the conversion efficiency. The measurements were made using different degrees of focusing of the beam in the crystal. The average power of the fundamental-frequency radiation varied between 0 and 20 W under frequency summation conditions and between 0 and 5 W when the yellow line was doubled.