NEAR-FIELD OPTICAL MICROSCOPY OF NONLINEAR SUSCEPTIBILITIES

Local probing of second-order susceptibilities with a near-field optic al microscope is demonstrated for the first time. Using an uncoated fi ber tip as a light source, near-field images of a surface of y-cut LiN bO3 crystal and of a multilayer Langmuir-Blodgett film of 2-docosylami no-5-nitropyridine are obtained at the fundamental pump and second har monic wavelengths while simultaneously recording surface topography. I t:is shown that optical second-harmonic images for different polarizat ions of the pump light reflect the difference in magnitude of the corr esponding components of the second-order susceptibility tensor. Variou s degrees of correlation in contrast of optical (fundamental and secon d harmonic) and topographical images are observed and discussed. (C) 1 998 Elsevier Science B.V. All rights reserved.