Characterization of photorefractive materials by spontaneous noncolinear frequency doubling

'Spontaneous' noncolinear frequency doubling (SNCFD) is a type of optical s econd-harmonic generation (SHG) that uses scattered light to provide additi onal fundamental beams in order to accomplish noncolinear phase matching. B ased on a novel algorithm for the automated evaluation of the resulting rin g patterns, we present an easy-to-apply, sensitive, and non-destructive met hod for the characterization of photorefractive materials, yielding two-dim ensional spatial resolution. As applications of the technique, examples for the characterization of lithium niobate crystals are presented.