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Acta Physica Sinica

DECISIVE INFLUENCE OF THE DYNAMIC BEHAVIOR OF THE ATOMIC DIPOLE MOMENT ON THE QUANTUM STATISTICAL PROPERTIES OF LASER FIELD

HUANG WEN-JIN, Huang Hu, Shiqun Li, 清华大学现代应用物理系，北京 100084

Published Jan 1, 1998• 1 citation
Publisher

Abstract

In this paper we derive the Fokker-Planck equation of a closed lasing system by using ordering techniques of operators, reduce it to an equation including merely field variables, and then obtain the Q function of the laser field. Through analyzing the Q function, we discover that,at the operating point, the dynamic behavior of the dipole moment between the lasing levels decisively influences the quantum statistical properties of the laser field. Under certain conditions we obtain a clear picture about the influence. The conclusion can be applied to a variety of laser systems, including those without inversion.

DOI
10.7498/aps.47.756

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In this paper we derive the Fokker-Planck equation of a closed lasing system by using ordering techniques of operators, reduce it to an equation including merely field variables, and then obtain the Q function of the laser field. Through analyzing the Q function, we discover that,at the operating point, the dynamic behavior of the dipole moment between the lasing levels decisively influences the quantum statistical properties of the laser field. Under certain conditions we obtain a clear picture about the influence. The conclusion can be applied to a variety of laser systems, including those without inversion.
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A recent analysis of the influence of the pump statistics on the laser output fluctuations is applied to the experimentally feasible case of a laser being pumped by light coming from a separate pump field cavity that is driven by a broad-band squeezed vacuum plus a coherent driving field. In contrast to the 'squeezed-reservoir laser', where a reservoir of squeezed modes coming from all directions coupled to the dipole moment of the lasing transition and leads to atomic phase decay inhibition and phase locking of the laser field, here the squeezed light merely pumps the gain atoms, that is gives rise to inversion of the laser transition. In analogy to photodetection theory the photon statistics of the laser output is calculated as a function of the photon statistics of the absorbed squeezed pump light. For the case of a squeezed pump field chosen to display sub-Poissonian statistics, it is demonstrated that the Mandel Q-parameter of the laser cavity output can theoretically reach the optimum value of Q=- 1 / 2 , similar to the case of a deterministic pumping mechanism.