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Communications in Physics

Influence of magnetic field and temperature on negative refractive index in a degenerate three-level atomic system

Bang Nguyen Huy, Luong Thi Yen Nga, Ai Nguyen Van, Le Van Doai

Published Nov 28, 2025• 0 citations
Publisher

Abstract

This work investigates the manipulation of the negative refractive index in a degenerate three-level \( \Lambda \)-type atomic system in the presence of an external magnetic field and Doppler broadening. The results show that the bandwidth of the negative refractive index can be significantly broadened by increasing the coupling laser intensity; for example, when \( \Omega_c \) increases from \( 30\gamma \) to \( 60\gamma \), the bandwidth expands from \( [0.5\gamma, 1.5\gamma] \) to \( [1.2\gamma, 4\gamma] \). The spectral position can be flexibly tuned by adjusting the magnetic field, shifting toward lower (higher) frequencies for \( B = -1\gamma_c \) (\( B = 2\gamma_c \)). Temperature has a pronounced effect on both the range and amplitude; increasing the temperature from \( 200\,\mathrm{K} \) to \( 400\,\mathrm{K} \) narrows the range from \( [-1.6\gamma_c, -0.2\gamma_c] \) to \( [-1.1\gamma_c, -0.5\gamma_c] \). These findings may facilitate experimental realization and potential practical applications of EIT-based negative-index materials.

DOI
10.15625/0868-3166/22871

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This work investigates the manipulation of the negative refractive index in a degenerate three-level ( \Lambda )-type atomic system in the presence of an external magnetic field and Doppler broadening. The results show that the bandwidth of the negative refractive index can be significantly broadened by increasing the coupling laser intensity; for example, when ( \Omega_c ) increases from ( 30\gamma ) to ( 60\gamma ), the bandwidth expands from ( [0.5\gamma, 1.5\gamma] ) to ( [1.2\gamma, 4\gamma] ). The spectral position can be flexibly tuned by adjusting the magnetic field, shifting toward lower (higher) frequencies for ( B = -1\gamma_c ) (( B = 2\gamma_c )). Temperature has a pronounced effect on both the range and amplitude; increasing the temperature from ( 200,\mathrm{K} ) to ( 400,\mathrm{K} ) narrows the range from ( [-1.6\gamma_c, -0.2\gamma_c] ) to ( [-1.1\gamma_c, -0.5\gamma_c] ). These findings may facilitate experimental realization and potential practical applications of EIT-based negative-index materials.
Abstract We have achieved a negative refractive index with significantly reduced absorption in a three-level Λ-type atomic gas medium under Doppler broadening. It shows that the conditions for obtaining negative refractive index in the presence of Doppler broadening are very different from those of Doppler broadening absent. In particular, in order to obtain negative refractive index in the case of Doppler broadening the coupling laser intensity must be approximately ten times greater than that when the Doppler broadening is ignored. Meanwhile, the frequency band of negative refractive index with Doppler broadening is significantly expanded (about a hundred times) compared to that without Doppler broadening, however, the amplitude of negative refractive index decreases with increasing temperature (or Doppler width). Even in some cases as temperature (Doppler width) increases, the left-handedness of the material can disappear. In addition, we also show that the amplitude and the frequency band of negative refractive index can be changed by adjusting the intensity and the frequency of coupling laser. Our theoretical investigation can be useful for selection of laser parameters under different temperature conditions to achieve negative refractive index in experimental implementation.
In this paper, we present the study on negative refractive index in an inhomogeneously broadened four-level inverted-Y atomic medium based on electromagnetically induced transparency (EIT). The expressions of the relative permittivity and the relative permeability are derived under Doppler broadening. For this four-level system, we have found two frequency bands of negative refractive index in an optical region corresponding to two EIT windows. The influences of coupling and signal laser fields as well as temperature on frequency bands of negative refractive index are investigated. Our research can be convenient for experimental implementation with real atomic media under different temperatures.
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.
Multicolor manipulation of negative refraction in a three-level Λ atomic system is theoretically investigated.Based on multicolor coherence, the negative refractive index can be obtained with reduced absorption.The refractive index can also be controlled by changing the sum of the phases of the sidebands in the trichromatic driving fields.By adjusting the sum phase, the refractive index can be varied between negative and positive in two different frequency bands.Furthermore, the frequency band corresponding to the negative refractive index is widened by increasing the intensity and the frequency difference of the trichromatic field.
Abstract The optical response of a magnetic-degenerated four-level atom system to the two left and right circular polarization components of the probe field is represented at room temperature. The absorption spectrum and group index for the two polarization components of the probe field are controlled according to the static magnetic field and the coupling field under electromagnetically induced transparency condition. By varying the strength of the static magnetic field, the optical response of the atomic medium can be changed from transparency to absorption or vice versa and hence the amplitude of group index also changes from positive extreme to negative extreme or vice versa. The same phenomenon also occurs when changing the coupling field intensity. In addition, temperature also significantly influence on the optical response of the atomic medium, which changes not only the amplitude but also the sign of the group index as the temperature increases. Our analytical results can be useful for experimental observation and related applications of light group index/velocity at room temperature.
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.