Room-temperature 1.06- to 0.53-μm second-harmonic generation in LiNbO 3 with 0.6-mol % MgO doping

Abstract

Second harmonic generation (SHG) of 532-nm radiation from 1064-nm radiation in LiNbO 3 doped with 0.6 mol% MgO has been investigated by using pulsed Nd:YAG lasers whose pulse duration is less than 25 nanoseconds. Efficient and noncritically phase-matched SHG has been achieved at room temperature without any severe photorefractive problem. SHG conversion efficiency of 50% was typically obtained with a 9.5-mm-long crystal and a fundamental peak-power density of 22 MW/cm 2 and 0.8 GW/cm 2 when the pulse duration of Nd:YAG laser are 25 ns and 40 ps, respectively. It was found that thermal heating due to a linear optical absorption and nonlinear intensity-dependent absorption cause a saturation of conversion efficiency for SHG with nanosecond and picosecond pulses, respectively. It is also observed that photorefraction occurs when the intensity of a fundamental laser is higher than 4 GW/cm 2 only for SHG with picosecond pulses. These experimental results show that LiNbO 3 doped with 0.6 mol% MgO is one of the best nonlinear optical crystal for an application to SHG with pulsed Nd:YAG lasers.