Optical Characterization of Quasi-monomolecular Layers of the Nonlinear Polymer polyDCHD-HS

The nonlinear optical properties of quasi-monomolecular layers of polyDCHD- HS spun on silver-coated plates were measured by Surface Plasmon spectroscopy at 1064 nm and with ps pulses. A surprisingly large value of chi(3) was obtained (Abs(Chi(3)) > 10-17 m2/V2). This value was related with the presence of the silver film, whose nanostructured surface provides an electromagnetic mechanism for the enhancement of the nonlinearity through local field effects. This point was confirmed by SERS experiments performed on-resonance (515 nm) and off-resonance (647 nm) on the same samples. The interaction of the p–conjugated system of the polymer chain with the silver surface is proposed to account for the experimental data.