Photoinduced reversible refractive index changes in doped poly(methyl methacrylate) lightguides

Planar polymer lightguides of poly(methyl methacrylate)(PMMA) doped with the azo dye, N,N-dihexyl-4-amino-4′-nitro-azobenzene (DHANA) were fabricated on a suitable glass substrate or on one surface of a regular prism. The absorption of this azo dye is strong in the green spectral region. With the red light of a HeNe laser (633 nm) these polymer films may be used as lightguides. However, in this spectral region, the guided light influences the waveguiding properties of the polymer film, making this combination a possible candidate for an all optical device material. The observed refractive index changes are intensity dependent and the response time is of the order of 100ms.