Substantial scattering of a weak coherent beam by a single atom

In order to observe substantial interaction between single atoms and photons, cavities with a high finesse can be used to enhance the field at the location of an atom. Alternatively, an attempt can be made to tailor the spatial mode of a photon to closely match the mode corresponding to an electrical dipole transition of an atom by strong focusing. In this paper, we present our experimental work on measurements of extinction and phase shift of a weak coherent beam due to the presence of an atom in the strongly focused part of a Gaussian light beam.