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Annalen der Physik

Radiation Properties of a Continuously Pumped Two‐Atom System

Heinz Steudel, Th. Richter

Published Jan 1, 1978• 27 citations
Publisher

Abstract

Abstract Radiation rate, angular distribution, spectrum, and intensity correlations of the radiation of a continuously pumped two‐atom system are calculated using Lehmberg's master equation and the fluctuation‐regression theorem. As one remarkable result we found that under certain conditions an increasing radiation rate can be accompanied by a spectral narrowing, see Fig. 4.

DOI
10.1002/andp.19784900205

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Physical Review•Dec 2, 1966•7 citations
Abstract Radiation rate, angular distribution, spectrum, and intensity correlations of the radiation of a continuously pumped two‐atom system are calculated using Lehmberg's master equation and the fluctuation‐regression theorem. As one remarkable result we found that under certain conditions an increasing radiation rate can be accompanied by a spectral narrowing, see Fig. 4.
Radiation properties of three atoms continuously pumped by an incoherent excitation mechanism are investigated by using Lehmberg's master equation (1970) and the quantum fluctuation-regression theorem. The main results are: (i) the radiation rate of three atoms within a volume of diameter very much less than lambda essentially depends on their arrangement; (ii) the effect for two atoms, i.e. that an increasing radiation rate can be accompanied by a decreasing spectral width, becomes even more pronounced for three atoms.
The intensity correlation function of the cooperative radiation from a continuously pumped three-atom system is calculated using Lehmberg's master equation supplemented by an incoherent-pumping term. Cooperative effects are found to change drastically the intensity fluctuations of the emitted radiation. Particularly, if the pumping rate is adjusted to three times the single-atom spontaneous decay rate, increased radiation, compared with that from three independently emitting atoms, should be observed, exhibiting a reduced intensity fluctuation.
We have solved a master equation to obtain the diagonal elements of the density matrix for laser light. The master equation represents a generalization of a master equation derived earlier for a single radiation mode interacting with NNN stationary two-level atoms. The generalization takes into account the pumping scheme which characterizes a three-level laser. For positive temperatures and a lossless cavity, the equilibrium solution of the master equation gives the correct statistical-mechanical description of the atoms and radiation. For negative temperatures, the distribution function for the number of photons in the mode is either exponential or peaked, depending on whether the laser is operating below or above threshold. The calculated intensity fluctuations are in good agreement with semiclassical results for lasers operating slightly above threshold.
Abstract The total radiation rate of the cooperative spontaneous emission from an initially single‐quantum excited three‐atom system is calculated using Lehmberg's master equation and taking into account dipole‐dipole near field interaction. We find a strong influence of the precise configuration of the atomic dipoles and of the position of the initially excited atom on the temporal behaviour of the total radiation rate, especially if the atoms are separated by distances much smaller than the resonance wavelength.
The steady-state intensity distribution for a laser operating somewhat above threshold is determined by solving a master equation. The master equation describes the interaction between a single radiation mode and NNN two-level atoms, it contains the effects of pumping and radiation loss from the cavity, and it is applicable to both homogeneous and Doppler broadening. Forms of the master equation applicable to both three- and four-level lasers are considered. Solutions are obtained under the assumption that the distribution of atoms and radiation intensity is a bivariate Gaussian. Fluctuations in the output of giant-pulse lasers are also considered.