Nondestructive detection of atoms bouncing on an evanescent wave

Abstract

A cloud of atoms reflecting from an evanescent-wave mirror produces a phase shift on the beam producing the evanescent wave. This shift can be used to detect the passage of the atoms. We give a physical discussion of this process and estimate the phase shift. The shift can be greatly increased by using a resonant planar waveguide. We also estimate the signal-to-noise ratio and show how to optimize the experimental parameters of such a measurement. Using the waveguide we find a signal-to-noise ratio of order of 300 in a realistic experimental situation.