Microlight: Lasing with Single Atoms

O. V. Astafiev, K. Inomata, A. O. Niskanen +4 more

Jaw-Shen Tsai, O. V. Astafiev, K. Inomata +4 more

H. J. Carmichael, Luis A. Orozco

Kyungwon An

Contrary to the conventional approach of maximizing the so-called beta factor for thresholdless lasing, we utilized collective interaction of phase-aligned atomic dipoles in a high-Q cavity to demonstrate thresholdless lasing even with a beta factor of 0.03 in the setting of the single-atom superradiance.

Sahel Ashhab, J. R. Johansson, Alexandre M. Zagoskin +1 more

We consider a system composed of a single artificial atom coupled to a cavity mode. The artificial atom is biased such that the most dominant relaxation process in the system takes the atom from its ground state to its excited state, thus ensuring population inversion. A recent experimental manifestation of this situation was achieved using a voltage-biased superconducting charge qubit. Even under the condition of 'inverted relaxation', lasing action can be suppressed if the 'relaxation' rate is larger than a certain threshold value. Using simple transition-rate arguments and a semiclassical calculation, we derive analytic expressions for the lasing suppression condition and the state of the cavity in both the lasing and suppressed-lasing regimes. The results of numerical calculations agree very well with the analytically derived results. We start by analyzing a simplified two-level-atom model, and we then analyze a three-level-atom model that should describe accurately the recently realized superconducting artificial-atom laser.

Sheng-Wen Li, Moochan B. Kim, G. S. Agarwal +1 more

We study the statistics of the lasing output from a single atom quantum heat engine, which was originally proposed by Scovil and Schulz-DuBios (SSDB). In this heat engine model, a single three-level atom is strongly coupled with an optical cavity, and contacted with a hot and a cold heat bath together. We derive a fully quantum laser equation for this heat engine model, and obtain the photon number distribution for both below and above the lasing threshold. With the increase of the hot bath temperature, the population is inverted and lasing light comes out. However, we notice that if the hot bath temperature keeps increasing, the atomic decay rate is also enhanced, which weakens the lasing gain. As a result, another critical point appears at a very high temperature of the hot bath, after which the output light become thermal radiation again. To avoid this double-threshold behavior, we introduce a four-level heat engine model, where the atomic decay rate does not depend on the hot bath temperature. In this case, the lasing threshold is much easier to achieve, and the double-threshold behavior disappears.