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Journal of Modern Optics

Magneto-optical control of the group velocity of light in an inhomogeneously broadened medium

Paul S. Hsu, Sukesh Roy, James R. Gord, Anil K. Patnaik

Published Apr 8, 2010• 3 citations
Publisher

Abstract

We investigate the use of a magnetic field, in conjunction with an elliptically polarized laser field, to control the group velocity of light in an inhomogeneously broadened medium. We show both theoretically and experimentally that the dispersion and hence, the speed of light in an atomic system, having V-configuration with Zeeman sublevels as their excited states, can be effectively controlled magneto-optically. We present approximate analytical solutions for a homogeneously broadened medium and numerical solutions for both a homogeneously and an inhomogeneously broadened medium. We show that while one can tune the speed of light from subluminal to superluminal with the magnetic field in a static or cooled medium with V-type atoms, in hot atoms one can achieve an efficient magneto-optical tunability in the subluminal regime. We experimentally demonstrate such control of light speed using a single elliptically polarized light and a moderately strong magnetic field in a 87Rb vapor cell. We propose to use the optical field for coarse control and the magnetic field for finer control of the light speed in an atomic medium.

DOI
10.1080/09500341003692997

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We investigate the use of a magnetic field, in conjunction with an elliptically polarized laser field, to control the group velocity of light in an inhomogeneously broadened medium. We show both theoretically and experimentally that the dispersion and hence, the speed of light in an atomic system, having V-configuration with Zeeman sublevels as their excited states, can be effectively controlled magneto-optically. We present approximate analytical solutions for a homogeneously broadened medium and numerical solutions for both a homogeneously and an inhomogeneously broadened medium. We show that while one can tune the speed of light from subluminal to superluminal with the magnetic field in a static or cooled medium with V-type atoms, in hot atoms one can achieve an efficient magneto-optical tunability in the subluminal regime. We experimentally demonstrate such control of light speed using a single elliptically polarized light and a moderately strong magnetic field in a 87Rb vapor cell. We propose to use the optical field for coarse control and the magnetic field for finer control of the light speed in an atomic medium.
Abstract We proposed a simple model for investigating subluminal and superluminal light propagation via an external magnetic field in an inhomogeneously broadened degenerate two-level atomic medium. We show that a magnetic field can be utilized as a knob to control the absorption/dispersion properties and group index of the medium. By changing the magnitude and reversing the direction of the magnetic field, the positive group index is converted to the negative group index at the center of the EIT window, corresponding with the propagation of a weak light pulse from subluminal to superluminal. Moreover, the influence of the Doppler broadening effect on the group index is also included, making the results approach to actual conditions. Therefore, the suggested model may be helpful for the application realization of optical storage in quantum computers and quantum information processing.
In this work, we proposed a simple model for control of subluminal and superluminal light propagation via an external magnetic field in a lambda configuration degenerate two-level atomic medium. We show that the absorption-dispersion properties and group index under the influence of the strength of coupling laser and external magnetic fields are controlled. By changing the direction and magnitude of the magnetic field, the medium switches from transparency with normal dispersion to enhanced absorption with anomalous dispersion at the line center, corresponding with the transfer from slow light to fast light. This work may provide for the application realization of magneto-optic switches and storage devices in quantum information processing.
Abstract The present study addresses light propagation in both the positive- and negative-group-index regimes in a degenerate atomic system with four energy levels. Both the static magnetic field and the Doppler shifts play essential roles. Operating in an electromagnetically induced transparency configuration, we demonstrate that probe absorption characteristics and the group velocity index can be manipulated by combined control of the static magnetic field and two coupling laser fields. By selectively engaging one or both coupling fields, the magnetic field serves as a switching mechanism, toggling the atomic medium's optical behavior between transparent and absorptive states. Consequently, both the magnitude and sign of the group index can be adjusted, transitioning from positive to negative values or the reverse, based on whether the magnetic field is applied or removed. Additionally, temperature significantly influences both the optical properties and group index characteristics of the atomic medium. Given that our proposed system operates at room temperature, it is well-suited to practical experimental conditions and offers potential for deployment in optical storage technologies and quantum information processing applications.
We were able to arbitrarily control the speed of a light pulse from subluminal to superluminal velocity by changing only the power of the laser for coupling coherently the single transition between 62S1/2F=46{}^{2}{S}_{1/2}F=462S1/2​F=4 and $6{}^{2}{P}_{3/2}{F}^{\ensuremath{'}}=5$ in the D2{D}_{2}D2​ line of a Cs atomic vapor system. With weak coupling power, a Gaussian light pulse was propagated superluminally with a negative group velocity ${v}_{g}=\ensuremath{-}c/14400,$ which is caused by a highly anomalous dispersion related to an electromagnetically induced absorption. By increasing the coupling power at the same laser frequency, the pulses were propagated with a vacuum speed at the middle power and a subluminal group velocity vg=c/3000{v}_{g}=c/3000vg​=c/3000 at high power, which is caused by a normal dispersion related to an electromagnetically induced transparency. It was also found that group velocities depend largely on polarization combinations.
Abstract In this paper we investigate the optical properties of an open four-level tripod atomic system driven by an elliptically polarized probe field in the presence of the external magnetic field and compare its properties with the corresponding closed system. Our result reveals that absorption, dispersion and group velocity of probe field can be manipulated by adjusting the phase difference between the two circularly polarized components of a single coherent field, magnetic field and cavity parameters i.e. the atomic exit rate from cavity and atomic injection rates. We show that the system can exhibit multiple electromagnetically induced transparency windows in the presence of the external magnetic field. The numerical result shows that the probe field in the open system can be amplified by appropriate choice of cavity parameters, while in the closed system with introduce appropriate phase difference between fields the probe field can be enhanced. Also it is shown that the group velocity of light pulse can be controlled by external magnetic field, relative phase of applied fields and cavity parameters. By changing the parameters the group velocity of light pulse changes from subluminal to superluminal light propagation and vice versa.