Refractive Index Change of an Amorphous Bisbenzothienylethene

A bisbenzothieneylethene exhibiting a photochromic behavior in the amorphous bulk solid state was synthesized. Upon alternate ultraviolet (UV) and visible light irradiation the amorphous thin film underwent a reversible color change and modulation of the refractive index. The refractive index change was determined at 632.8 nm and 817 nm using a prism coupling method. The difference in the refractive index value between the open- and closed-ring isomers was as high as 0.064 at 817 nm.