Determination of Linear and Nonlinear Optical Properties of a Polymer Thin Film

The second- and third-order nonlinear susceptibilities gC(2) and gC(3) of a polymer thin film are determined for three wavelengths (543.Snm, 632.8nm and 1523nm) using a method based on the linear and quadratic electro-optic effect. The frequency dependences of gC(2) and gC(3), deduced from a simple two-level electron-spring model, are consistent with our experimental results. Using this frequency dependence the intensitydependent refractive index, determined by nonlinear grating coupling, is transformed to a gC(3) value for the quadratic electro-optic effect. This value is in good agreement with our experiments. The layer structure used is simple and consists basically of a polymer layer sandwiched between thin metal electrodes.