An effective strategy to achieve deeper coherent light for LiB3O5

Abstract

LiB₃O₅ (LBO), although with high nonlinearity, is angular non-phase matched in deep ultraviolet second harmonic generation (SHG) processes due to its small birefringence. The structural configuration distortion is a promising way to improve the birefringence. By means of first principles computations, the effect of strain along the a, b and c-axes on the birefringence of LBO is systematically predicted in this work. We find that the birefringence can be effectively and considerably enhanced (to 0.075 at 266 nm) by applying a rather weak strain (0.42 GPa) along the c-axis. Such a strain-induced increase in the birefringence of LBO is favourable for extending the shortest wavelength that can be produced by means of the SHG process. The results indicate that strain-engineering is an effective strategy for enhancing birefringence, which behaves like a switch to control the generation of deeper coherent light output for some nonlinear optical crystals.