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Modern Physics Letters A

Superluminal propagation of light in a atomic medium

Najm Uddin, Meraj Ali Khan

Published Sep 14, 2024• 0 citations
Publisher

Abstract

We manipulated and adjusted the absorption, dispersion, group index, and group velocity in a sodium atomic medium by controlling the strength and collective phase of the driving fields. The group index in these regions is calculated to be [Formula: see text]250,000. The group velocity [Formula: see text] in these locations is measured to be [Formula: see text][Formula: see text]m/s. An investigation is conducted on a negative delay of [Formula: see text]s in the sodium medium. The presence of negative delay and negative group velocity indicates the occurrence of superluminal propagation of light pulses within the medium. The negative group index is increased from [Formula: see text] to [Formula: see text], and the negative delay time is increased from [Formula: see text]s to [Formula: see text]s, with the driving field [Formula: see text] having a Rabi frequency. The work presented in this paper has substantial implications for the fields of gravitational wave detection, radar technology, and temporal cloaks.

DOI
10.1142/s0217732324501335

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We manipulated and adjusted the absorption, dispersion, group index, and group velocity in a sodium atomic medium by controlling the strength and collective phase of the driving fields. The group index in these regions is calculated to be [Formula: see text]250,000. The group velocity [Formula: see text] in these locations is measured to be [Formula: see text][Formula: see text]m/s. An investigation is conducted on a negative delay of [Formula: see text]s in the sodium medium. The presence of negative delay and negative group velocity indicates the occurrence of superluminal propagation of light pulses within the medium. The negative group index is increased from [Formula: see text] to [Formula: see text], and the negative delay time is increased from [Formula: see text]s to [Formula: see text]s, with the driving field [Formula: see text] having a Rabi frequency. The work presented in this paper has substantial implications for the fields of gravitational wave detection, radar technology, and temporal cloaks.
Abstract We used a theoretical approach to study and investigate that how light pulses move faster than light in a four level atomic medium. In this study Laguerre-Gaussian (LG) beam waist, represented by F and strength Z is controlled. We examine the localized absorption and dispersion characteristics inside the four level atomic medium, illustrating that altering the beam waist affects the group velocity. According to the findings that we obtained, the group velocity at lower beam waists is between -0.0004c to -0.0002c, and the group index is negative, ranging from -0.0015 to -0.0005 respectively. As the pulse waist expands the extent of localized absorption and dispersion widens, yet the superluminal performance stays unchanged. Potentially useful in fields such as gravitational wave detection, soliton radar systems, and high-speed optical computing, this study sheds fresh information on the adaptability of light propagation in dispersive surfaces.
The area devoted to cross-Kerr nonlinearity and coherent driving fields is increasingly used to control optical solitons in atomic media. Recently, this area has been investigated by using the concepts of fractals theory. Since then, fractals theory has various applications in different disciplines of science and engineering. The said area has the capability to describe the complex geometry of dynamical problems. The propagation of light pulse and their solitonic behavior are investigated in a [Formula: see text] medium of four levels. Significant control over the absorption, dispersion, group refractive index and pulse propagation is reported with variation of coupled driving fields. The sublominal group velocity of [Formula: see text] and superlominal propagation of group velocity of [Formula: see text] is controlled. The bright and dark soliton pulse is modified with variation of driving fields in the superluminal and sublominal regions. Due subluminality of light dark soliton is reported and superluminality bright soliton is noted in the medium. The maximum of [Formula: see text] output pulse intensity is controlled. The intensity of the output pulse is an increasing and decreasing function of coupled driving fields’ Rabi frequencies. The modified solitons in this rubidium atomic medium are comparably more informative and significant to solitonic pulse intensity control in four-level cesium atomic medium under Doppler and inverse Doppler broadening effects. The modified results have useful application and soliton radar and communication technologies.
Abstract Light-matter interaction between a light field and an atomic medium could be used to manipulate the medium’s dispersive properties, leading to subluminal and superluminal regimes. Utilizing the same idea, this work investigates the propagation of structured superluminal light and anomalous phase shifts in a Λ- type three-level atomic medium, where a structured control field governs the atomic system. The absorption and dispersion properties are modulated by the azimuthal quantum number (ℓ) of the control field. The maxima and minima of the absorption spectrum, along with the corresponding normal and anomalous dispersion peaks, are enhanced with a (2ℓ) dependence on the azimuthal quantum number in the medium. The negative group index and anomalous phase shift vary within the ranges −1000 ≤ ng ≤ −900 and −6.5 × 10 5 ≤ ϕ ≤ −5.6 × 10 5 rad, respectively. The corresponding group velocity lies in the range −3.33 × 10 5 ≤ vg ≤ −3.0 × 10 5 m/s within the spatial region −2λ ≤ x, y ≤ 2λ. Furthermore, the anomalous phase shift is significantly enhanced in regions exhibiting superluminal behavior, following the (2ℓ) azimuthal quantum number dependence. The findings of this work may have potential applications in optical storage devices, imaging, coding, and the design of advanced photonic technologies.
Summary form only given. We use gain-assisted linear anomalous dispersion to demonstrate superluminal light pulse propagation with a negative group velocity through a transparent atomic medium. We place two Raman gain peaks closely to obtain an essentially lossless anomalous dispersion region that results in a superluminal group velocity. The group velocity of a pulse in this region exceeds c and can even become negative,while the shape of the pulse is preserved. We measured a negative group velocity index of n/sub g/=-315(/spl plusmn/5). Experimentally, a light pulse propagating through the spin-polarized atomic vapor cell exits from it earlier than propagating through the same distance in vacuum by a time difference that is 315 times of the vacuum light propagation time L/c=0.2 ns.
We studied and investigated whether light pulses travel faster then light in a four-level atomic medium using a theoretical method. Laguerre-Gaussian (LG) beam waist, denoted by F and strength Z, is regulated in this investigation. We analyses the localized absorption and dispersion properties within the four level atomic medium as well as demonstrate how the group velocity is affected by changing the beam waist. Our results showed that the team index remained negative, with values spanning -0.0015 to -0.0005, and the speed of the group at reduced beam-like waists was among -0.0004 and -0.0002 c. While the superluminal capability remains constant, the level of localized absorption as well as dispersion increases with the pulse waist. This work provides new insights into the flexibility of light propagation on dispersive surfaces, which may be helpful in domains like gravitational wave motion detection methods, soliton scanning systems, and high-frequency optical computation.
We studied and investigated whether light pulses travel faster then light in a four-level atomic medium using a theoretical method. Laguerre-Gaussian (LG) beam waist, denoted by F and strength Z, is regulated in this investigation. We analyses the localized absorption and dispersion properties within the four level atomic medium as well as demonstrate how the group velocity is affected by changing the beam waist. Our results showed that the team index remained negative, with values spanning -0.0015 to -0.0005, and the speed of the group at reduced beam-like waists was among -0.0004 and -0.0002 c. While the superluminal capability remains constant, the level of localized absorption as well as dispersion increases with the pulse waist. This work provides new insights into the flexibility of light propagation on dispersive surfaces, which may be helpful in domains like gravitational wave motion detection methods, soliton scanning systems, and high-frequency optical computation.