OPTICAL-PHASE GRATINGS MADE FROM PHOTOREFRACTIVE POLYMERS

Based on a combination of surface structure and refractive index modifications, an optical phase grating was fabricated from a thin film of photoreactive polymers, which had been synthesized from methyl methacrylate and a methacrylic ester including nonconjugate carbon-carbon double bonds, and doped with an aromatic ketone. After exposure to ultraviolet light beams through a photomask with a grating pattern, the exposed portion of the polymer film was up to ˜110% thicker and ˜3% higher in refractive index than the unexposed portion. Diffraction efficiencies of light beams passing through the optical phase grating varied with its cross-sectional shape. © 1990 Optical Society of America.