Nonlinear optical properties of oligothiophene self-assembled monolayers on gold substrate

Liner and nonlinear-optical proper-ties of oligothiophenes self-assembled monolayers (SAM) are studied by optical second harmonic interference technique. Linear polarizability and first hyperpolarizability as functions of the number of thiophene rings are calculated using a self-consistent approach for linear and nonlinear optical properties. Both of these dependencies can be described by a power law; a nonzero first hyperpolarizability points to the asymmetry of delocalized electron system that might be due to an adsorption of thiophene molecules on a metal substrate.