Second-harmonic imaging from a modulated domain structure

We present a new second-harmonic (SH) imaging technique to study the domains in a hexagonally poled LiTaO3 nonlinear photonic crystal by using a femtosecond laser. By detecting the SH images at different planes, the distribution of the 180 degrees-inverted ferroelectric domains can be characterized, and the contributions of different nonlinear tensor components, modulated differently in the domain structure, can be selectively determined. Fundamental understanding and potential applications of such SH imaging techniques for the inverted nonlinear domain structures are presented and discussed. (C) 2010 Optical Society of America