Polymeric thin films for integrated optics.
This thesis presents the results from the characterisation of the linear optical properties of various polymers and the energy transfer process between several dye pairs in polymeric waveguides. The polymers and dyes were considered for their use in solid state thin film wavelength tuneable light sources. The optical waveguiding properties of the polymers were investigated, and the results of the experiments are reported. Also the fundamental concepts of wave guiding in thin films are presented. The techniques of processing the thin films, input and output coupling of the light and analysis of the results is discussed. The mechanism of non-radiative energy transfer between dye pairs was investigated as a means of efficiently exciting the acceptor dye. The theory is discussed. Also the results of both the steady state and time resolved experiments, used to determine the efficiency of the process, are reported. Efficient energy transfer has been observed in a rhodamine dye system and also between newly developed BASF dyes. Several models are proposed to explain an up conversion observed in a dye doped polymer waveguide. Here fluorescence was observed by exciting the dye in the long wavelength tail of the absorption band. A model based on the thermal population of electrons to higher vibrational levels, from where they can be promoted to the first excited electronic state, is shown to best explain the phenomenon.