Large photoinduced refractive index change in a polyimide film by charge-transfer complex formation with a polymer-bound phenylazide fragment

A large photo-induced refractive index change as large as 0.014 at 632.8 nm in thermostable transparent polymer films has been realized for the first time by using photoirradiation of polyimide precursor films containing a ph enylazide and successive imidization. The phenylazide fragment forms a char ge-transfer complex with imide moiety. The films maintained high transmitta nce in a wide visible region in contrast to usual polyimide films. This val ue of refractive index change is sufficient to make thermostable channel wa veguides and other optical devices.