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Refractive indices of organic photochromic dye-amorphous polymer composites and their changes upon photo- irradiation were measured. The packing coefficients of the dyes in amorphous polymers were determined, and it becomes possible to estimate the refractive indices of the polymer composites containing various amounts of dyes. Molar refractions [R] at 633 nm were also determined for both isomers of the dyes.

Fabrication of a photooptical switching device based on the photo-induced refractive index change of polymer film doped with photochromic compounds is described. 1,2-bis(2-methylbenzo[b]thiophen-3-yl) perfluorocyclopentene (BFCP) and 1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene (CMTE) were used as the photochromic compounds. A transformation in the compounds from the opened-ring to closed-ring form was induced by irradiation with a He–Cd laser (325 nm) and the reverse reaction with an Ar ion laser (488 nm). The polymer films containing BFCP and CMTE showed a refractive index change, Δn, as large as 5×10-4/ wt% photoisomerized chromophores. Photooptical switching of a prism-coupling device was demonstrated by alternate irradiation with Ar ion and He–Cd lasers, and also by irradiation with a pulsed YAG laser.

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Graded-index plastic optical fiber whose transmission attenuation is 143 dB/km at 651-nm wavelength was fabricated by heat-drawing the corresponding GI preform rod. This rod is prepared by the interfacial-gel copolymerization technique of methyl methacrylate (MMA) and vinyl phenylacetate (VPAc). The total scattering loss of the GI preform rod is ~60 dB/km at 633 nm. The graded-index profiles of the optical fibers are almost the same as those of the corresponding preforms with cladding sheaths. The index distributions of their core regions are quadratic against the distance from the center axis. The numerical aperture estimated from the index difference is ~0.20.