Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Communications in Theoretical Physics

Subluminal and Superluminal Phenomena in a Four-Level Atom

Han Ding-An, Yaguang Zeng, Cao Hui

Published Jul 1, 2008• 3 citations
Publisher

Abstract

In a four-level atomic system, we investigate the light pulse propagation properties interacting with only one laser field. It is shown that in the steady state, the group velocity of the light pulse can be changed from subluminal to superluminal by varying the field detuning. Meanwhile, the effects of the field intensity on the group velocity are also shown. At last, with special parameters, the analytical solution for the group index is also obtained.

DOI
10.1088/0253-6102/50/1/38

Related papers

SGC Switching Between Subluminal to Superluminal Propagation in V-Type Atom

Han Ding-An, Hong Wei Guo, Bai Yanfeng +2 more

For a V-type three-level atomic system with two closely spaced upper levels, we investigate the light pulse propagation properties with only one laser field. Due to spontaneously generated coherence, the group velocity of the light pulse can be changed from subluminal to superluminal. The effects of the field intensity and the two-upper level splitting on the group velocity are also shown. At last, an analytical expression for the group velocity is given in the case of a weak field.

Communications in Theoretical Physics•Oct 1, 2006•13 citations

Control of the group velocity of a light pulse propagating through a four-level atomic system

P A Grochowska, Andrzej Raczyński, Jarosław Zaremba +1 more

We analyse the group velocity of a laser pulse in an optically dressed atomic system. A Λ system with an additional close upper level and an incoherent pump is specially investigated. The group velocity of a pulse is strongly dependent on the optical properties of the system which can be modified by changing the amplitude or detuning of a strong coupling field or of an incoherent pump between the two lower levels of the system. Depending on the parameters, the medium may have alternatively absorptive or gain properties and the dispersion can be changed from anomalous into a normal one. The ranges of parameters are especially investigated in which absorption (gain) is not too strong, with dispersion being not too steep. The group velocity of a pulse propagating through a sample with such optical properties can be switched from the subinto superluminal regime. The dynamics of propagation in the case of negative group velocities of a small absolute value is especially interesting. In such a regime the peak of the transmitted pulse exits the sample before the peak of the incoming pulse reaches the medium. The transmitted pulse splits into two pulses - one of them propagates forward behind the medium and the other propagates backward and is cancelled at the entrance of the sample by the incoming pulse. Ranges of parameters are seeked in which the shape of the pulse is changed and the group velocity as a single parameter is not sufficient to describe the pulse propagation.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•May 5, 2011•1 citation

Switching between superluminal to subluminal velocities and Tunable slow light in a four level atomic system

Sankar Davuluri, Yuri V. Rostovtsev

A four-level atomic system interacting with two strong drive fields and a weak probe field has been studied. We demonstrate that the group velocity of probe field can be controlled to switch from subluminal to superluminal or even negative values around the probe resonance without any significant absorption. The basic idea is to create a gain with slow light on the probe beam resonance with one drive field while the other drive creates a dip in the gain profile of probe leading to superluminal and negative group velocities. A simple switching from slow light to negative group velocity light can be obtained by changing the relative intensities of drive fields. We also describe a control to tune the position of slow light frequency continuously simply by adjusting the relative intensities of both the driving fields.

Journal of Physics Conference Series•Feb 8, 2013•10 citations

Switching from subluminal to superluminal light propagation via a coherent pump field in a four-level atomic system

Shang-qi Kuang, Ren-Gang Wan, Jun Kou +2 more

We theoretically investigate the influence of a coherent pump field on the propagation of a weak light pulse of a probe field in a four-level atomic system. Due to the modulation of the pump field, the light pulse can be manipulated from subluminal to superluminal with negligible distortion. This scheme can be realized in both the ultracold and Doppler-broadened atomic systems. We also demonstrate that the spectral linewidth with an anomalous dispersion is reduced by thermal averaging; therefore, one can obtain a larger negative group refractive index in room-temperature vapor than the largest value achieved in ultracold atomic gas.

Journal of the Optical Society of America B•Nov 5, 2009•13 citations

Switching from normal dispersion to anomalous dispersion in a four-level atomic system

Zhi‐Hui Kang, Fan Meng, Yan-Ji Qu +4 more

Abstract The manipulation of the group velocity of light is very important in further information processing and quantum network. It is well known that subluminal and superluminal light propagation can be obtained by controlling the dispersion property of the experimental medium. In order to realize the switching from normal dispersion to anomalous dispersion at the same frequency, we investigate the dispersion and absorption properties of a four-level atomic system. By adjusting the intensity of an incoherent pump, we get transparent normal dispersion and lossless anomalous dispersion, which lead to subluminal and superluminal light propagation respectively. For a strong incoherent pump, the intensity of the coherent coupling field also can be used to realize a similar switching effect.

Laser Physics•Oct 19, 2021•1 citation

Superluminal reflection and transmission of light pulses via resonant four-wave mixing in cesium vapor

Qichang Jiang, Yan Zhang, Dan Wang +3 more

We report the experimental manipulation of the group velocities of reflected and transmitted light pulses in a degenerate two-level atomic system driven by a standing wave, which is created by two counter-propagating light beams of equal frequencies but variable amplitudes. It is shown that the light pulse is reflected with superluminal group velocity while the transmitted pulse propagates from subluminal to superluminal velocities via changing the power of the backward coupling field. We find that the simultaneous superluminal light reflection and transmission can be reached when the power of the backward field becomes closer or equal to the forward power, in this case the periodical absorption modulation for photonic structure is established in atoms. The theoretical discussion shows that the anomalous dispersion associated with a resonant absorption dip within the gain peak due to four-wave mixing leads to the superluminal reflection, while the varying dispersion from normal to anomalous at transparency, transparency within absorption, and electromagnetically induced absorption windows leads to the subluminal to superluminal transmission.

Optics Express•Oct 12, 2016•6 citations
In a four-level atomic system, we investigate the light pulse propagation properties interacting with only one laser field. It is shown that in the steady state, the group velocity of the light pulse can be changed from subluminal to superluminal by varying the field detuning. Meanwhile, the effects of the field intensity on the group velocity are also shown. At last, with special parameters, the analytical solution for the group index is also obtained.
We analyse the group velocity of a laser pulse in an optically dressed atomic system. A Λ system with an additional close upper level and an incoherent pump is specially investigated. The group velocity of a pulse is strongly dependent on the optical properties of the system which can be modified by changing the amplitude or detuning of a strong coupling field or of an incoherent pump between the two lower levels of the system. Depending on the parameters, the medium may have alternatively absorptive or gain properties and the dispersion can be changed from anomalous into a normal one. The ranges of parameters are especially investigated in which absorption (gain) is not too strong, with dispersion being not too steep. The group velocity of a pulse propagating through a sample with such optical properties can be switched from the subinto superluminal regime. The dynamics of propagation in the case of negative group velocities of a small absolute value is especially interesting. In such a regime the peak of the transmitted pulse exits the sample before the peak of the incoming pulse reaches the medium. The transmitted pulse splits into two pulses - one of them propagates forward behind the medium and the other propagates backward and is cancelled at the entrance of the sample by the incoming pulse. Ranges of parameters are seeked in which the shape of the pulse is changed and the group velocity as a single parameter is not sufficient to describe the pulse propagation.
A four-level atomic system interacting with two strong drive fields and a weak probe field has been studied. We demonstrate that the group velocity of probe field can be controlled to switch from subluminal to superluminal or even negative values around the probe resonance without any significant absorption. The basic idea is to create a gain with slow light on the probe beam resonance with one drive field while the other drive creates a dip in the gain profile of probe leading to superluminal and negative group velocities. A simple switching from slow light to negative group velocity light can be obtained by changing the relative intensities of drive fields. We also describe a control to tune the position of slow light frequency continuously simply by adjusting the relative intensities of both the driving fields.
We theoretically investigate the influence of a coherent pump field on the propagation of a weak light pulse of a probe field in a four-level atomic system. Due to the modulation of the pump field, the light pulse can be manipulated from subluminal to superluminal with negligible distortion. This scheme can be realized in both the ultracold and Doppler-broadened atomic systems. We also demonstrate that the spectral linewidth with an anomalous dispersion is reduced by thermal averaging; therefore, one can obtain a larger negative group refractive index in room-temperature vapor than the largest value achieved in ultracold atomic gas.
Abstract The manipulation of the group velocity of light is very important in further information processing and quantum network. It is well known that subluminal and superluminal light propagation can be obtained by controlling the dispersion property of the experimental medium. In order to realize the switching from normal dispersion to anomalous dispersion at the same frequency, we investigate the dispersion and absorption properties of a four-level atomic system. By adjusting the intensity of an incoherent pump, we get transparent normal dispersion and lossless anomalous dispersion, which lead to subluminal and superluminal light propagation respectively. For a strong incoherent pump, the intensity of the coherent coupling field also can be used to realize a similar switching effect.
We report the experimental manipulation of the group velocities of reflected and transmitted light pulses in a degenerate two-level atomic system driven by a standing wave, which is created by two counter-propagating light beams of equal frequencies but variable amplitudes. It is shown that the light pulse is reflected with superluminal group velocity while the transmitted pulse propagates from subluminal to superluminal velocities via changing the power of the backward coupling field. We find that the simultaneous superluminal light reflection and transmission can be reached when the power of the backward field becomes closer or equal to the forward power, in this case the periodical absorption modulation for photonic structure is established in atoms. The theoretical discussion shows that the anomalous dispersion associated with a resonant absorption dip within the gain peak due to four-wave mixing leads to the superluminal reflection, while the varying dispersion from normal to anomalous at transparency, transparency within absorption, and electromagnetically induced absorption windows leads to the subluminal to superluminal transmission.