Type-I walk-off compensated second and fourth harmonic generation of Nd: YAG laser radiation from a Li

Abstract

A type-I walk-off compensation (WOC) arrangement has been made for the second harmonic generation (SHG) and the fourth harmonic generation (FOHG) of commercially available Q-switched Nd: YAG laser radiation, for the first time, using two identically cut Li2B4O7 crystals. The enhancement of the conversion efficiencies has been realized in the WOC arrangement by a factor of 2.71 for the SHG and 2.65 for the FOHG relative to the double-crystal non-walk-off arrangement. The absolute values of the conversion efficiencies obtained for WOC SHG and FOHG are 3.52% and 3.56% respectively, applying input power densities for the fundamental and second harmonic of the Nd: YAG laser beam at only 28.3 MW cm-2 and 11.7 MW cm-2, respectively. © 2001 IOP Publishing Ltd.