Fabrication of surface relief grating with second-order nonlinearity using urethane-urea copolymer films

Surface relief gratings on azobenzene-substituted urethane-urea copolymer films with large second-order nonlinearity are fabricated by a laser-interferometric method. The surface relief structures are obtained upon exposure to an interference pattern of a polarized Ar+ laser beam, which mainly results from photoablation. The gratings are thermally stable at temperatures higher than glass transition temperature (T-g) of the copolymer. The surface relief gratings with second-order nonlinearity are fabricated after a corona poling process. We report what we believe to be the first experimental observation of the separated second-harmonic generation from the fundamental wave by the surface relief grating with second-order nonlinearity.