Abstract

We describe a fundamental laser system, the microlaser, in which a single atom in teracts with a single mode of the radiation field.¹ In the experiments a beam of ¹³⁸Ba atoms inverted on the ¹S₀ → ³P₁ transition at λ = 791 nm traverses an ultrahigh Q supercavity resonator. The excited atoms interact with the cavity one by one and emit photons into the resonator. Because of the long cavity storage time, a large number of photons can build up. As the average number of atoms in the cavity mode, N̄, increases from 0.1 to 1, the average number of photons in the cavity mode, $\overline{v}$, increases from 0.1 to 12. Anomalously large signals are observed when N̄ approaches unity and $\overline{v}$ is much larger than one. This behavior results from the standing-wave nature of the cavity mode, in combination with the saturation effect occurring at large cavity photon number. Spontaneous emission is negligible in the microlaser system. Therefore, unlike conventional lasers, it plays no role and amplification occurs via quantized Rabi oscillations,^2,3 which are the underlying manifestation of the stimulated emission process. The large energy and momentum associated with optical photons opens the possibility of studying new aspects of cavity QED, including the generation of photon-number trapped states and the study of entanglement of internal and mechanical degrees of freedom. This presentation shall review the current status of our microlaser research.

© 1995 Optical Society of America