Novel Photoactive Nonlinear Optical Polymers for Use in Optical Waveguides

Photoactive polymers were developed for use in waveguide delineation, which affords the opportunity to laterally define a waveguide through lowering the refractive index in optically exposed areas. Synthesis of a series of photosensitive polymers was reported and their photochemical kinetic behavior characterized. The photoactive group was a dinitrostilbene chromophore which was incorporated as a side chain pendant on a methacrylate backbone. Results obtained revealed that, on irradiation, the chromophore electronic absorption maximum underwent both a hypsochromic shift and oscillator strength reduction which was shown to manifest as a refractive index reduction of more than 0.05 at 1.3 μm. A full investigation of the photochemical kinetic behavior was completed along with analysis of both electronic absorption and infrared spectral data of the bleached polymers. As a comparison, the kinetic behavior of current chromophores utilized in nonlinear optical devices, the nitrostilbene and (dicyanovinyl)hexatriene, as well as the o-nitro-p cyanostilbene, was also evaluated. For all chromophores, the donor group was an amine. Kinetic experiments confirmed that the dinitrostilbene chromophore was indeed, quantitatively, the most sensitive and that, in solution, a quantum efficiency as high as 0.11 was measured. The polymers synthesized exhibited promising photochemical properties which would make them interesting waveguide cladding materials, either incorporated in the active layer as lateral cladding or imposing a dielectric loading as the upper cladding layer.