Quantum-dot microlaser operating on the whispering gallery mode - A source of squeezed (sub-Poissonian) light

The reduced density matrix method is used to calculate the quantum-statistical properties of the radiation of a quantum-dot laser operating on the whispering gallery mode of a dielectric microsphere. It is shown that under the conditions of strong coupling between the quantum dot and an electromagnetic field the radiation of such a laser can be in a nonclassical (sub-Poissonian) state. The laser scheme considered is characterized by an extremely low lasing threshold and a small number of saturation photons, as result of which lasing is possible with close to zero population inversion of the working levels, if g much greater than P much greater than gamma much greater than Gamma, where g is the field-matter interaction constant, P is the pumping rate, gamma is the loss rate of the resonator, and Gamma is the spontaneous emission rate. The largest squeezing inside the resonator-microsphere (the Fano factor F = 0.75) obtains for g much greater than P much greater than gamma much greater than Gamma, and the greatest squeezing in the fluctuation spectrum outside the resonator [V(omega = 0) approximate to 0.25] occurs for g similar to P similar to gamma much greater than Gamma, and in this case a substantial deviation of the photon number statistics of the radiation leaving the resonator from the Poissonian statistics is observed. (C) 2000 MAIK "Nauka/ Interperiodica".