Frequency doubling in SBN crystals with random ferroelectric domains in the thermal focusing regime

Abstract

We consider the femtosecond phase-matched noncollinear second-harmonic generation (SHG) in Strontium Barium Niobate (SBN) crystals with random ferroelectric domains. We study both planar and radial second-harmonic (SH) radiation for the average input power Pf up to 600 mW. We show that the effect of thermal self-focusing of the fundamental wave occurring at Pf > 250 mW results in novel effects including the spatial localization of SHG, a change of the SH efficiency slope, and significant spectral broadening of both fundamental and SH beams.