REFRACTIVE-INDEX CHANGE IN PHOTOCHROMIC DIARYLETHENE DERIVATIVES AND ITS APPLICATION TO OPTICAL SWITCHING DEVICES

The refractive index change of photochromic diarylethene derivatives i n solid polymer was studied with a view to fabricating an optical swit ching device. The reaction time required for a symmetric diarylethene photochromic compound in a copolymer of fluoroethyl methacrylate and m ethyl 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, meas ured with a prism coupler, was 0.0005 per 10 wt.% of diarylethene phot ochromic compound. The iteration number of the photochromic reactions in the polymer film decreased in the following order: symmetric, asymm etric diarylethene and acid anhydride. We propose a new type of self-h olding optical switch combining a heat stable photochromic material wi th silica planar lightwave circuits. (C) 1997 Elsevier Science S.A.