Tunable quasi-phase matching using dynamic ferroelectric domain gratings induced by photorefractive space-charge fields

Abstract
We demonstrate a method of dynamic, tunable quasi‐phase matched second‐harmonic generation using optically induced polarization gratings with periods equal to twice the coherence length. These gratings increase the peak second‐harmonic conversion efficiency by a factor of 17 above a poled strontium barium niobate crystal, to 0.01% for fundamental beam intensities of 0.8 MW cm−2. We generate quasi‐phase matching spectral response peaks as narrow as 0.175 nm and tailor the response by writing an ensemble of gratings in the same volume, each of which enhances the second‐harmonic generation at a predetermined wavelength.