The intensity fluctuation distribution of laser light

Observation of grand-canonical number statistics in a photon Bose-Einstein condensate

We report measurements of particle number correlations and fluctuations of a photon Bose-Einstein condensate in a dye microcavity using a Hanbury Brown-Twiss experiment. The photon gas is coupled to a reservoir of molecular excitations, which serve as both heat bath and particle reservoir to realize grand-canonical conditions. For large reservoirs, we observe strong number fluctuations of the order of the total particle number extending deep into the condensed phase. Our results demonstrate that Bose-Einstein condensation under grand-canonical ensemble conditions does not imply second-order coherence.

Photon number distributions from a diode laser

We use balanced homodyne detection to characterize light from a diode laser as it crosses the threshold. We measure the single-time second-order correlation function g(2), and also extract the photon number distribution. Just above the laser threshold, we find that the measured g(2) exceeds the prediction of the semiclassical single-mode laser model. From the reconstructed photon number distributions, we conclude that this excess is due to emission from nonlasing modes. For higher pumping current, the light noise increases due to a different mechanism, possibly mode competition or mode partition noise.

Squeezed light from conventionally pumped multilevel lasers

We calculate amplitude squeezing spectra for the light from a variety of conventionally pumped three- and four-level lasers. Hence we extend a recent prediction that a certain three-level laser can generate nonclassical light without the need for rigged pumping.