Observation of multiple thresholds in the many-atom cavity QED microlaser

We report the observation of multiple laser thresholds in the many-atom cavity QED microlaser. Traveling-wave coupling and a supersonic atom beam are used to create a well-defined atom-cavity interaction. Multiple thresholds are observed as jumps in photon number due to oscillatory gain. Although the number of intracavity atoms is large, up to $N\sim {10}^3$, the dynamics of the microlaser agree with a single-atom theory. This agreement is supported by quantum trajectory simulations of a many-atom microlaser and a semiclassical microlaser theory. We discuss the relation of the microlaser with the micromaser and conventional lasers.

Figure 1

Schematic of cavity QED microlaser. M: Cavity mirrors, C: Cavity mode, AB: Atomic beam from oven, A: Collimating aperture, P: Pump field (into page), $\theta$: Cavity tilt angle, LP: Locking probe beam. Dashed line is normal to cavity axis.

Figure 2

Gain (solid line) and loss (dashed line) per atom transit in the rate equation analysis [left and right sides of Eq. (1), respectively] including effects of velocity distribution, nonuniform coupling, and detuning, with $N_{\mathrm{eff}}=1000$. Closed circles: Stable solutions. Open circles: Unstable solutions.

Figure 3

Photon number $n$ versus effective atom number $N_{\mathrm{eff}}$ for cavity locking experiment. Circles $(엯)$: “Unseeded” data; Crosses $(\times )$: “Seeded” data. Solid line: Rate equation model, solution of Eq. (1) for experimental parameters.

Figure 4

Cavity tuning line shapes. Estimated photon number $n$ versus atom-cavity detuning ${\Delta }_{\mathrm{cav}}$. Solid lines, positive frequency scan. Dashed lines, negative frequency scan. Estimated effective intracavity atoms: (a) $N_{\mathrm{eff}}=18$, (b) $N_{\mathrm{eff}}=526$, (c) $N_{\mathrm{eff}}=657$, and (d) $N_{\mathrm{eff}}=755$.