Refractive index change in photochromic diarylethene derivatives and its application to optical switching devices

The refractive index change of photochromic diarylethene derivatives in solid polymer was studied with a view to fabricating an optical switching device. The reaction time required for a symmetric diarylethene photochromic compound in a copolymer of fluoroethyl methacrylate and methyl methacrylate (film thickness: 10 mu m) was 20-30 s when exposed to UV light (intensity: 5.3 mW cm(-2) at 350 nm) to form a closed ring and about 10 s with visible light (intensity: 3.7 mW cm(-2) at 500 nm) to form an open ring. The refractive index change at 1.30 mu m, measured with a prism coupler, was 0.0005 per 10 wt.% of diarylethene photochromic compound. The iteration number of the photochromic reactions in the polymer film decreased in the following order: symmetric, asymmetric diarylethene and acid anhydride. We propose a new type of self-holding optical switch combining a heat stable photochromic material with silica planar lightwave circuits. (C) 1997 Elsevier Science S.A.