Counting Photons from a Laser Polariton Condensate

When the power of the light driving a laser exceeds the lasing threshold, the laser’s active medium enters a state in which the atoms sync their emission to produce coherent laser light. Researchers have studied this coherent state by counting the photons emitted from a laser, deriving a statistical distribution of the probability that 1, 2, or n photons are emitted at a given time. Martin Klaas at the University of Würzburg, Germany, and colleagues have now performed similar photon-counting experiments to shed light on another recently discovered coherent state of matter known as an exciton-polariton condensate.