Thermal-pulse investigation of poled nonlinear optical polymers

Poled nonlinear optical (NLO) polymer films are usually supported by substrates. This leaves two possibilities for investigating polarization and electric-field profiles in such samples with the thermal-pulse-technique: Thermal-pulse generation in the front electrode on the film or in the rear electrode between film and substrate. The influence of the substrate on the amplitude and on the long-time behavior of the thermal-pulse signal is theoretically treated. Experiments were performed on a poled double-layer sample consisting of a polymer film with NLO chromophores adhered to a similar polymer without chromophores, the latter film adhered to the substrate. The results demonstrate the validity of the proposed experimental approach.