Photooptical Switching of Polymer Film Waveguide Containing Photochromic Diarylethenes

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.