Noncolinear Second-Harmonic Generation Pairs and Their Scatterings in Nd^3+:SBN Crystals with Needle-Like Ferroelectric Domains

Second-harmonic generation in Nd^3+:SBN crystal with needle-like ferroelectric with aperiodic domain structures is investigated. Two pairs of second harmonic (SH) waves appearing in lines are observed in unpoled Nd^3+:SBN crystals with aperiodic needle-like domains. A pair of SH waves emit from the exit face, whose intensities are angle-dependent. The angular dependence is corresponding to the spatial frequency spectrum of the aperiodic domain structure. Another pair of SH waves emit from both the side surfaces, which are mainly the scattered SH waves by needle-like domain walls and obey the theory of Rayleigh scattering.