Optical Dipole Noise of Two-Level Atoms

Abstract

We measure phase-dependent optical noise spectra for a simple system: long-lived coherently driven two-level atoms in an atomic beam. Very different noise spectra are measured for radiation which is in phase and out of phase with the driving field. The spectra and corresponding analysis afford clear insights into the roles played by three distinct sources of atomic noise. The measured noise spectra are in good agreement in magnitude and shape with results of a quantum treatment using no free parameters.