Gaussian beam scattering by a particle above a plane surface

We derive a theory to calculate light scattering from a particle above an infinite plane surface and with Gaussian beam illumination. The incident Gaussian beam is expanded in series of cylindrical vector wave functions, and the scattered as well as internal fields in series of spherical ones. The integral representation of spherical vector wave functions over cylindrical waves is used to compute the reflection of the scattered field by the surface. By applying the boundary conditions and the projection technique, the unknown expansion coefficients of the scattered field are determined. For a localized beam model, numerical results of the normalized differential scattering cross sections are presented, and the scattering characteristics are discussed concisely.