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Journal of Physics B Atomic Molecular and Optical Physics

Electromagnetically induced transparency of the medium composed of atoms in thermal motion

Tianhui Qiu, Guojian Yang

Published Oct 12, 2011• 0 citations
Publisher

Abstract

We investigate electromagnetically induced transparency of a medium composed of N Λ-type three-level atoms in thermal motion with an initial momentum distribution modelled by a Gaussian function. We treat atomic centre-of-mass motion as an independent degree of freedom and study the dependence of susceptibility on the thermal motion characterized by the width and centre of Gaussian momentum distribution. A larger width does not always lead to larger resonant absorption and if the probe and controlling fields copropagate in the degenerate and resonant cases, transparency can be obtained regardless of the thermal motion of the atoms.

DOI
10.1088/0953-4075/44/21/215503

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Electromagnetically induced transparency (EIT) in an inhomogenously broadened medium consisting of Λ-type three-level atoms has been analyzed. It is shown that the Λ system can induce a transparency of the medium when the probe laser and the coupling laser have the same frequency detunings (including zero). Across the EIT window, the radial variation of the strong coupling laser radiation may lead to electromagnetically induced focusing or defocusing of the weak probe laser at separate probe frequency detuning points.
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We studied the electromagnetically induced transparency, where the three-level atom of Λ-type is put in two statistically independent squeezed vacuums. We start from the master equation containing the decay of the atom to the squeezed vacuums, and solve the non-diagonal density matrix element analytically, finding that it is strongly dependent on the squeezing degree and the phase of the squeezed vacuum. There is also a dependence on the intensity and phase of the probe beam, which would not appear in the normal vacuum case. By coupling with squeezed vacuums, the atom would not only experience electromagnetically induced transparency and slow group velocity, but also induce a fast group velocity,backward group velocity and a gain in the probe light field. Besides, the absorption and gain can be modulated by the intensity of probe light.