Spectroscopy of dressed-atom states

Abstract

Gain arising from the interaction of intense laser fields and atoms has attracted recent attention because it has been found, for example, that two-photon lasing1 and lasing without inversion2 occurs in these systems. Physical and intuitive models of these interactions can be developed by using the dressed-atom states, which, unfortunately, tend to be difficult to detect directly with high precision. We will report on a new modulation spectroscopy for the quantum limited detection of gain in dressed-atom systems. The spectroscopy involves weak modulation of the dressed-state splitting and lockin detection of the intensity of the probing beam. It differs from classic frequency-modulation spectroscopies in that the probe beam is not modulated before it interacts with the sample of strongly driven atoms and hence does not suffer from the effects of residual amplitude modulation.