TUNABLE QUASI-PHASE MATCHING USING DYNAMIC FERROELECTRIC DOMAIN GRATINGS INDUCED BY PHOTOREFRACTIVE SPACE-CHARGE FIELDS

We demonstrate a method of dynamic, tunable quasi-phase matched second -harmonic generation using optically induced polarization gratings wit h periods equal to twice the coherence length. These gratings increase the peak second-harmonic conversion efficiency by a factor of 17 abov e a poled strontium barium niobate crystal, to 0.01% for fundamental b eam intensities of 0.8 MW cm-2. We generate quasi-phase matching spect ral response peaks as narrow as 0.175 nm and tailor the response by wr iting an ensemble of gratings in the same volume, each of which enhanc es the second-harmonic generation at a predetermined wavelength.