Stable surface relief grating with second-order nonlinearity on urethane–urea copolymer film

Abstract Surface relief gratings (SRGs) on azobenzene-contained urethane–urea copolymer film with second-order nonlinearity are fabricated by laser-interferometric method. The surface relief structures are obtained upon exposure an interference pattern of a CW Ar+ laser and a single-pulse UV laser. The SRG is thermally stable even at Tg of the copolymer. The mechanism of the stability is investigated by comparing the pulse UV laser inscribed SRG. It is suggested that laser ablation of the copolymer surface by the high-power laser irradiation is taken into account. Second-order nonlinearity is induced by corona-poling process after grating formation. Diffraction of second-harmonic generation (SHG) is observed by inserting a fundamental beam, which is in agreement with vector diagram.