Abstract

We present initial results demonstrating operation of a "microlaser", a laser oscillator operating in the quantum limit with a small number of atoms in the resonator. This fundamental system should enable study of the quantum mechanical interaction of a single two-level atom with the single mode of an optical cavity in the regimes of stimulated emission and phase coherent gain. It is the optical analog of the micrornaser developed by Walther and his collaborators¹. The experiments employ the 1S₀-³P₁ barium transition (λ=791 nm, τ=3.5 µs). The atoms, inverted by means of π -pulse excitation, pass through a high-Q supercavity optical resonator (finesse ≈ 106). This system operates in the Rabi-oscillation regime, and the atoms have not reached a steady state as they exit the cavity. The rate of inflow of excited atoms can be made much larger than the loss rate, determined by cavity decay and atomic spontaneous emission. At present, operation has been obtained with 10-100 atoms in the cavity, with a mean number of photons ranging from 3-30. We have measured the output power as a function of the intensity and position of the pump laser and the flux of the excited atoms. The results indicate that single atom operation will be possible with a longer optical cavity with increased finesse, and improved pumping efficiency. Initial results on photon statistics will be presented.

© 1994 Optical Society of America