LINEAR-POLYMERS FOR NONLINEAR OPTICS .4. SYNTHESIS AND NONLINEAR-OPTICAL PROPERTIES OF SIDE-CHAIN POLY(METHACRYLATES) WITH VINYLCYANOSULFONYL GROUPS

Several polymers containing amino-azobenzene-vinylcyanosulfonyl chromophores were synthesized by free-radical polymerization of methacrylate-functionalized monomers. The polymers were soluble and could be spin-coated into somewhat brittle but acceptable quality films. After poling, one sample displayed a large electrooptic coefficient, r(33), of 22 pm/V (measured off-resonance at 830 nm). Also, the electrooptic response of this sample was quite stable, retaining approximately 90% of its original r(33) after storage for 2 months at 80 degrees C. Light at 1064 nm could be successfully propagated in thin-film waveguides, but polymers containing a high concentration of the chromophore had unacceptable absorption losses at 830 nm. The absorption at 830 nm was attributed to a small amount of chromophore-aggregate in the solid film that led to a broadening of the absorption spectrum of the chromophore. Attempts to suppress the formation of the aggregated species using variations in terminal groups, spacer lengths, and comonomer identity were unsuccessful. Only rather large dilution of the chromophore gave a material capable of waveguiding 830 nn light, with a proportional decrease in nonlinear optical susceptibility.