Synthesis and characterization of dye-containing fluorinated polyimide thin films

Abstract Lightguiding polyimide based thin films have been extensively studied for their good optical properties. By doping the polyimide matrix with different concentrations of dye molecules, active structures can be produced. In this work, thin films of fluorinated polyimide containing rhodamine B (RB) have been obtained by a two-step solvent based method. The precursor resin has been spin coated on silica substrates and cured at temperatures ranging from 80 to 250°C, providing about 5 μm thick films. 4,4′-Hexafluoroisopropylidene bis diphthalic anhydride (6FDA) and 4,4′-diaminobenzophenone (DAB) have been used as precursor monomers. Dye concentration ranging from 0.5 to 1.5 wt.% has been chosen. Optical emission and absorption spectra have been collected in order to study spectroscopic and aggregation characteristics of rhodamine as a function of doping and curing parameters. The waveguiding properties and the refractive index of the films have been analyzed by prism coupling method.