Large and Stable Refractive Index Change in Photochromic Hybrid Materials

We have developed new transparent photochromic hybrid organic−inorganic materials in which the photochromic group belongs to the polymer network. These materials involving chemically bonded dithienylethene derivatives 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−gel films either at 633 or 785 nm were determined both in the colored and discolored state by using the attenuated total reflection (ATR) method. Functionalized sol−gel films showed a large refractive index change in a nonabsorbing spectral region: Δ n ≈ 4 × 10 - 2 at 785 nm. This important variation due to the high photochrome content allowed us to design optical components used in the field of wave guiding.