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 chromo phores 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 polin g, one sample displayed a large electrooptic coefficient, r(33), of 22 pm/V (measured off-resonance at 830 nm). Also, the electrooptic respo nse of this sample was quite stable, retaining approximately 90% of it s 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 unacce ptable absorption losses at 830 nm. The absorption at 830 nm was attri buted to a small amount of chromophore-aggregate in the solid film tha t led to a broadening of the absorption spectrum of the chromophore. A ttempts to suppress the formation of the aggregated species using vari ations in terminal groups, spacer lengths, and comonomer identity were unsuccessful. Only rather large dilution of the chromophore gave a ma terial capable of waveguiding 830 nn light, with a proportional decrea se in nonlinear optical susceptibility.