LARGE AND STABLE REFRACTIVE-INDEX CHANGE IN PHOTOCHROMIC HYBRID MATERIALS

We have developed new transparent photochromic hybrid organic-inorgani c materials in which the photochromic group belongs to the polymer net work. These materials involving chemically bonded dithienylethene deri vatives were prepared by the sol-gel process in the form of thin films a few microns thick. The thickness and refractive index of the sol-ge l films either at 633 or 785 nm were determined both in the colored an d discolored state by using the attenuated total reflection (ATR) meth od. Functionalized sol-gel films showed a large refractive index chang e in a nonabsorbing spectral region: Delta n approximate to 4 x 10(-2) at 785 nm. This important variation due to the high photochrome conte nt allowed us to design optical components used in the field of wave g uiding.