Conversion of radiation in nonlinear photonic crystals of strontium tetraborate

Strontium tetraborate (SBO) possesses transparency in the VUV that allows nonlinear generaton to the wavelengths as short as 125 nm. The existence of domain structures consisting of alternating oppositely poled domains is found in as grown crystals of SBO. Domain walls are perpendicular to a crystallographic axis. In this paper non-collinear generation (nonlinear diffraction) of the second and third harmonics of nanosecond Nd:YAG laser is used for the investigation of reciprocal superlattice vectors (RSV) spectrum of the domain structures. When fundamental radiation propagates in the vicinity of direction perpendicular to the domain walls, random quasi phase matching (RQPM) was observed in the process of generation of 266 nm radiation via doubling of the second harmonic of nanosecond Nd:YAG laser. Maximum efficiency of conversion is 0.5% and exceeds that obtained for 2D nonlinear photonic crystal based on strontium barium niobate.