Optical characterization of quasi-monomolecular layers of the nonlinear polymer polyDCHD-HS

Abstract

The nonlinear optical properties of quasi-monomolecular layers of polyDCHD-HS spun on silver-coated plates were measured using surface plasmon spectroscopy at 1064 nm and with ps pulses. A surprisingly large value of χ⁽³⁾ was obtained (|χ⁽³⁾| > 10⁻¹⁷ m² V⁻²). This value was related to 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. It is suggested that the experimental data can be accounted for by the existence of an interaction between the π-conjugated system of the polymer chain and the silver surface.