Simple method of detecting ferroelectric domains with non-phase-matched second-harmonic generation

We demonstrate a new method of detecting the presence of ferroelectric domains based on non-phase-matched second-harmonic generation. If a domain boundary is tilted relative to the input and output faces of the crystal, the far-field second-harmonic light consists of multiple beams, in contrast to the single beam generated in a single-domain crystal. The angular separation of the beams provides a measure of the tilt of the domain wall if the refractive-index difference n(2omega) - n(omega) is known.