It has been widely accepted that the conventional lasing threshold, occurring around unity intracavity photon number, can be eliminated by making the so-called $\beta$ parameter approach unity. Recently, it has been shown that the photon statistics become incoherent when the intracavity mean photon number is decreased below unity even for $\beta \approx 1$ . Here, we report systematic measurement of the photon statistics in a superradiant laser as a function of the intracavity photon number. Our superradiant laser was based on the single-atom superradiance driven by twolevel atoms in a quantum superposition state traversing a high-Q cavity one by one. The lasing did not exhibit the conventional threshold and the photon statistics remained near coherent even well below unity photon number. Moreover, the coherence got better as the excited-state population in the initial superposition state was made smaller.It has been widely accepted that the conventional lasing threshold, occurring around unity intracavity photon number, can be eliminated by making the so-called $\beta$ parameter approach unity. Recently, it has been shown that the photon statistics become incoherent when the intracavity mean photon number is decreased below unity even for $\beta \approx 1$. Here, we report systematic measurement of the photon statistics in a superradiant laser as a function of the intracavity photon number. Our superradiant laser was based on the single-atom superradiance driven by twolevel atoms in a quantum superposition state traversing a high-Q cavity one by one. The lasing did not exhibit the conventional threshold and the photon statistics remained near coherent even well below unity photon number. Moreover, the coherence got better as the excited-state population in the initial superposition state was made smaller.

International Conference on Transparent Optical NetworksJul 14, 20240 citations

A quasi-continuous superradiant Raman laser with < 1 intracavity photon

Justin Bohnet, Zilong Chen, Joshua M. Weiner +4 more

Steady-state collective emission from ensembles of laser cooled atoms has been proposed as a method for generating sub-millihertz linewidth optical lasers, with potential for broad impacts across science and technology. We have built a model system that tests key predictions for such active oscillators using a Raman laser with laser cooled atoms as the gain medium. The laser operates deep in the bad-cavity, or superradiant, regime of laser physics, where the cavity decay rate is much greater than the atomic coherence decay rate. Specifically, we demonstrate that a system of 106 87Rb atoms trapped in a 1D standing wave optical lattice can spontaneously synchronize and collectively emit a quasi-continuous coherent optical output, even when the intracavity field contains on average < 1 photon.Steady-state collective emission from ensembles of laser cooled atoms has been proposed as a method for generating sub-millihertz linewidth optical lasers, with potential for broad impacts across science and technology. We have built a model system that tests key predictions for such active oscillators using a Raman laser with laser cooled atoms as the gain medium. The laser operates deep in the bad-cavity, or superradiant, regime of laser physics, where the cavity decay rate is much greater than the atomic coherence decay rate. Specifically, we demonstrate that a system of 106 87Rb atoms trapped in a 1D standing wave optical lattice can spontaneously synchronize and collectively emit a quasi-continuous coherent optical output, even when the intracavity field contains on average < 1 photon.

EPJ Web of ConferencesJan 1, 20135 citations

A superradiant laser with

<1

intracavity photon

It has been widely accepted that the conventional lasing threshold, occurring around unity intracavity photon number, can be eliminated by making the so-called

\beta

parameter approach unity. Recently, it has been shown that the photon statistics become incoherent when the intracavity mean photon number is decreased below unity even for

\beta \approx 1

. Here, we report systematic measurement of the photon statistics in a superradiant laser as a function of the intracavity photon number. Our superradiant laser was based on the single-atom superradiance driven by twolevel atoms in a quantum superposition state traversing a high-Q cavity one by one. The lasing did not exhibit the conventional threshold and the photon statistics remained near coherent even well below unity photon number. Moreover, the coherence got better as the excited-state population in the initial superposition state was made smaller.