Theoretical analysis of light-inductive forces in scanning probe microscopy

Abstract

When two objects of subwavelength size interact in the presence of a light beam, a spatially confined electromagnetic field arises in a small spatial region located at the immediate proximity of the particles. In scanning probe microscopy, such induced short-range interactions change the magnitude of the forces interacting between the probe tip and the substrate. Depending on the frequency of light excitation with respect to those of the gap modes associated with the tip-sample junction, these inductive forces act to pull the probe toward the surface. Such an effect can be used to record optical adsorption of various samples with an atomic-force microscope. In this paper we show that the accurate description of the physical processes responsible for these forces can be analyzed within the framework of the localized field-susceptibility method. Practical solutions for the light-inductive force were found by discretization of the probe apex in real space. All multiple interactions including reflections with a substrate of arbitrary profile were accounted for by self-consistent procedures. We can therefore present simulations performed on systems of experimental interest. © 1994 The American Physical Society.