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Journal of the Optical Society of America B

Phase-dependent properties for absorption and dispersion by spontaneously generated coherence in a four-level atomic system

Wei-Hua Xu, Huifang Zhang, Jin-Yue Gao, Bing Zhang

Published Nov 1, 2003• 27 citations
Publisher

Abstract

A four-level atomic system with two closely lying upper levels driven by two coherent fields is considered. We show that, in the presence of a weak incoherent pump, steady-state gain can be achieved as a result of quantum interference from spontaneous emission. The gain depends on the relative phase between the two fields, so it can be modulated by control of the relative phase. Also, by controlling the relative phase, one can always obtain a large index of refraction with zero absorption.

DOI
10.1364/josab.20.002377

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A four-level atomic system with two closely lying upper levels driven by two coherent fields is considered. We show that, in the presence of a weak incoherent pump, steady-state gain can be achieved as a result of quantum interference from spontaneous emission. The gain depends on the relative phase between the two fields, so it can be modulated by control of the relative phase. Also, by controlling the relative phase, one can always obtain a large index of refraction with zero absorption.
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We studied a closed three-level V-type system with two near-degenerate excited levels in the presence of an incoherent pumping field. Quantum interferences of the two-decay channels lead to the achievement of the high index of refraction without absorption via spontaneously generated coherence. We use the exact analytical formula of the refractive index derived by us in a recent paper. We found that the high refractive index varies very much with the angle between the two dipole moments and evidently with the detuning of the coupling field.
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