Analyzing the polarization distribution in poled polymer films by scanningKelvin microscopy

We present a method for analyzing the homogeneity of the chi((2)) distribut ion in poled nonlinear optical polymer films. The second-order nonlinear co efficient in these polymers is commonly induced by electric-field poling me thods which can lead to a chi((2)) distribution with poor spatial homogenei ty. In this letter, we analyze the chi((2)) distribution using scanning Kel vin microscopy. This allows us to detect the height and the direction of th e induced polarization through the probing of the countercharges that are p resent on the polymer surface. We compare the response to that obtained fro m the scanning second-harmonic microscopy method, in which the direction of the orientation, and thus the phase of chi((2)), cannot be seen. (C) 2000 American Institute of Physics. [S0003-6951(00)00905-0].