Second-harmonic conversion of laser radiation generated under free-oscillation conditions

An investigation was made of the energy dependence of the efficiency of the second-harmonic conversion of the radiation emitted by a neodymium laser operating under free-oscillation conditions. A conversion efficiency of 0.105% was obtained for an angular divergence of 20'' and an energy density of 75 J/cm². The conversion was performed in a KDP crystal whose damage threshold was found to be 1100 J/cm².