Analyzing the polarization distribution in poled polymer films by scanning Kelvin microscopy

Abstract

We present a method for analyzing the homogeneity of the χ(2) distribution in poled nonlinear optical polymer films. The second-order nonlinear coefficient in these polymers is commonly induced by electric-field poling methods which can lead to a χ(2) distribution with poor spatial homogeneity. In this letter, we analyze the χ(2) distribution using scanning Kelvin microscopy. This allows us to detect the height and the direction of the induced polarization through the probing of the countercharges that are present on the polymer surface. We compare the response to that obtained from the scanning second-harmonic microscopy method, in which the direction of the orientation, and thus the phase of χ(2), cannot be seen.