Fundamental walkoff compensated SHG in KTP and LBO

本文分析了一种基本的离差补偿型SHG方案，并通过实验证明了该方案对KTP和LBO的有效性。在1064nm基波长下，KTP晶体切割角为28.5°，入射角为7°时获得了最大SH功率，与传统的24°切割晶体相比，12尼米长的KTP晶体的功率提高了20%。对于LBO，发现FWC II型SHG位于从Z (b)到Y(c)轴40度的晶体中。在最佳聚焦条件下，10mm长的FWC II型LBO的功率比传统的II型LBO（20度切割）提高了一倍，并且与LBO I型SHG功率几乎一致。这证明了在II型SHG中，两根基束间走偏补偿的重要性。该方案也适用于非线性器件应用，因为入射角是有限的（不垂直于SHG晶体），并且不会反向反射，这将导致不稳定的激光振荡。

A fundamental walkoff-compensated type II SHG scheme has been analyzed and its usefulness has been experimentally demonstrated for KTP and LBO.Maximum SH power was obtained at a crystal cut angle of 28.5 deg and an incident angle of 7 deg for KTP at a 1064nm fundamental wavelength, and a 20% power enhancement was observed in 12 nun long KTP compared with a conventional 24 deg cut crystal. For LBO, FWC type II SHG was found to ke place in the crystal cut at 40 deg from the Z (b) to the Y(-c) axes. Double power enhancement was observed for 10mm-long FWC type II LBO than for conventional type II LBO (20-deg cut) and almost coincides with LBO type I SHG power at an optimum focusing condition. this proves the importance of walkoff compensation between two fundamental beams in type II SHG.This scheme is also suitable for nonlinear device application because incident angles are finite (not normal to the SHG crystal) and do not retroreflect, which would result in unstable laser oscillation.