Revivals and Oscillations of the Momentum of Light in a Planar Multimode Waveguide

The evolution of the transverse momentum of monochromatic light entering a multimode planar waveguide at large angle is investigated. We report on oscillations of the momentum caused by the beatings between the adjacent populated modes of the waveguide and their periodic collapses and revivals. A new type of an interferometer based on this effect with fringe spacing as small as $\lambda /9\mathrm{}$ is demonstrated experimentally, and periods as small as $\lambda /1000\mathrm{}$ seem to be feasible.