Annealing induced variation in refractive index of Rhodamine B doped Poly (vinyl) alcohol films

The present paper reports the influence of fluorescent dye doping on the optical properties, in particular on the refractive index of Poly (vinyl) alcohol (PVA) host matrix. The dye (Rhodamine B) is doped in weight percent ranging from 0 to 2 wt%. It is found that at highest doping wt% (2%), dye molecules segregate to the surface breaking the bonds of the PVA matrix as well as simultaneously forming new bonds, thereby modifying the overall refractive index. Also, annealing of these samples produces a change in the refractive index. The refractive index shows a general decreasing trend with increasing wavelength but with modified values upon changing doping percentage or upon annealing. Overall results are interpreted in terms of bond modifications at the surface and interior of PVA due to the inclusion of Rhodamine B molecules.

► Polyvinyl alcohol films were doped with a range of Rhodamine B concentrations.
► At highest doping weight percent (2%), dye molecules break the bonds of PVA.
► New bonds are simultaneously formed, modifying the overall refractive index.
► Also, annealing of these samples produces change in the refractive index.
► Explained in terms of bond modifications at the surface and interior of PVA.