Optical forces on microparticles in an evanescent laser field.

We present a theory based on an exact calculation of the radiation forces on a microsized particle illuminated by evanescent waves created under total internal reflection in a flat substrate. The influence of the proximity of this interface to the particle is analyzed by a numerical simulation that addresses multiple scattering of light between the particle and the dielectric flat surface. We thus give an interpretation of the experimental results of Kawata and Sugiura [Opt. Lett. 17, 772 (1992)] and put forward a method that is capable of predicting new effects.