Abstract
The interaction of laser cooled atoms with resonant light is determined by the natural linewidth of the excited state. An optical cavity is another optically resonant system where the loss from the cavity determines the resonant optical response of the system. The near resonant combination of an optical Fabry-Pérot cavity with laser cooled and trapped atoms couples two distinct optical resonators via light and has great potential for precision measurements and the creation of versatile quantum optics systems. Here we show how driven magneto-optically trapped atoms in collective strong coupling regime with the cavity leads to lasing at a frequency red detuned from the atomic transition. Lasing is demonstrated experimentally by the observation of a lasing threshold accompanied by polarization and spatial mode purity, and line-narrowing in the outcoupled light. Spontaneous emission into the cavity mode by the driven atoms stimulates lasing action, which is capable of operating as a continuous wave laser in steady state, without a seed laser. The system is modeled theoretically, and qualitative agreement with experimentally observed lasing is seen. Our result opens up a range of new measurement possibilities with this system.
Highlights
While both cold atoms[1, 2] and cavity physics[3, 4] are central to atomic physics, few experiments combine an intra-cavity ensemble of cold atoms with a cavity[5,6,7,8,9,10,11,12,13]
In the experiments here we demonstrate that continuous lasing seeded by spontaneous emission from the driven, non-inverted population of atoms in the cavity mode is possible and robust under reasonable experimental conditions
The atomic ensemble is constantly illuminated by the six magneto-optical trap (MOT) light beams of 10 mm diameter and frequency red detuned by 13 MHz from the atomic transition (3-4′ transition of D2 line33)
Summary
While both cold atoms[1, 2] and cavity physics[3, 4] are central to atomic physics, few experiments combine an intra-cavity ensemble of cold atoms with a cavity[5,6,7,8,9,10,11,12,13]. The threshold behavior seen only in the red detuned peak in Fig. 2(c) is suggestive of lasing in this driven atomic system coupled to the cavity mode.
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