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COHERENTLY PUMPED MICROMASER AS A MASER WITHOUT INVERSION

M. Soltanolkotabi, M. H. Naderi

Published Jan 1, 2001• 0 citations
OpenAlex

Abstract

In this paper, we use microscopic maser theory developed by Filipovicz, Javanaien and Meystre [Phys. Rev. A 34, 3077 (1986)] to investigate the properties of the coherently pumped two-level micromasers. We flnd that under right conditions, the initial atomic coherence locks the fleld phase and unlike ordinary lasers and masers there is no longer threshold. Consequently, the population inversion is not necessary.

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Physical Review A•Jan 1, 1992•5 citations
In this paper, we use microscopic maser theory developed by Filipovicz, Javanaien and Meystre [Phys. Rev. A 34, 3077 (1986)] to investigate the properties of the coherently pumped two-level micromasers. We flnd that under right conditions, the initial atomic coherence locks the fleld phase and unlike ordinary lasers and masers there is no longer threshold. Consequently, the population inversion is not necessary.
When pumping produces atomic coherence on working levels or atomic polarization two-level atom can generate the light without inversion. In such systems one- and two-photon generation of the light is considered for the laser and micromaser operation. Using Lamb-Scully model generalized for coherent pumping statistics of the light is considered. Two-photon laser operation is found to be phase squeezed and perfect noise reduction can be achieved. In maser a set of steady state of subpoissian photon statistics is found. For these states the noise reduction up to 60 percent can be obtained if inversion is zero. Phase squeezing in micromaser is found.
We present the theory of a truly microscopic maser consisting of a single-mode high-Q resonator in which a monoenergetic beam of excited two-level atoms is injected at such a low flux that at most one atom at a time is present inside the cavity. Both a microscopic theory and a heuristic Fokker-Planck approach are presented. We show that the micromaser exhibits a number of novel features that are averaged out in usual masers and lasers. First, the field is in general sub-Poissonian, which reflects the quantization of both the field and its sources. Second, the onset of maser oscillations may be followed by a succession of abrupt transitions in the state of the field. Finally, as the atomic flux through the resonator is increased, the maser threshold acquires characteristics of a continuous phase transition, whereas the subsequent changes in the field distribution become analogous to first-order phase transitions.
We show that the problem of a \ensuremath{\Lambda}-type (and also a V-type) three-level single-mode laser (maser) is isomorphic to that of a two-level single-mode laser (maser) under the conditions of energy-level degeneracy and equal decay rates. This correspondence reveals that lasing without population inversion can occur in the \ensuremath{\Lambda}-type system with or without an initial atomic coherence, and also gives immediately the master equation of the laser (maser) field. We analyze in detail the operational and noise properties of a \ensuremath{\Lambda}-type laser using a Fokker-Planck approach. We also present a vector model to visualize the population trapping and the absorption and emission processes in such a laser (maser) system.
We present the quantum theory of a microscopic maser operating on a degenerate two-photon transition between levels of the same parity. We derive both a master equation and a Fokker-Planck equation for this system, and show that quantum effects may have a substantial influence on the behavior of the maser. They modify the oscillation threshold and make external triggering of this maser unnecessary, whereas, according to semiclassical theory, such a triggering is required to start up the maser oscillation. We derive the phase-diffusion properties of the field and show that the diffusion coefficient is complex in this case, its imaginary part being associated with a frequency shift of the field inside the cavity. We show that, in steady state, the photon-number statistics is sub-Poissonian for a wide range of pumping rates.
The lifetimes of Rydberg atoms have been considered in micromaser theory. The difference from the usual micromaser theory [P. Filipowicz, J. Javanainen, and P. Meystre, Phys. Rev. A 34, 3077 (1986)] without level decay rates is discussed. It is shown that when the atom-field interaction time is large, the quantum collapse and revival are significantly different from the prediction of the usual micromaser theory. The relation between the photon fluctuation and the fluctuation of the population of the lower level after interacting with a maser field is also discussed. We found that the consistency of the sub-Poisson statistics of the lower-level population and photon number is violated.