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Vinh University Journal of Science

MULTI-FREQUENCY GROUP VELOCITY CONTROL OF LIGHT IN Rb ATOMIC GAS UNDER AN EXTERNAL MAGNETIC FIELD

Nguyen Van Phu, VO Thi Hong Yen, Le Van Doai, Ho Hai Quang, THAI Van Ton, PHAN Duc Thuan, Le Nguyen Mai Anh

Published Sep 20, 2025• 0 citations
Publisher

Abstract

The control of light group velocity via electromagnetically induced transparency (EIT) has opened up potential applications in photonic technologies such as information encoding, quantum processing, and optical switching. For traditional three-level atomic systems only allow light control within a narrow frequency range, limiting multi-channel applications. To overcome this limitation, this study focuses on multi-frequency group velocity control in a 87Rb atomic medium under the influence of an external magnetic field. By combining the semiclassical theory with analytical methods, we derive the expressions for the absorption, dispersion, and group index of a four-level atomic system. Based on these results, we investigate the influence of the magnetic field and laser parameters on the absorption, dispersion, and group index. The findings not only shed light on the mechanism for controlling multi-frequency light, but also suggest potential directions for developing flexible photonic devices that meet the future demands of multi-channel information processing. Keywords: Electromagnetically induced transparency; light group velocity; external magnetic field; four-level atomic configuration

DOI
10.56824/vujs.2025a040a

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The control of light group velocity via electromagnetically induced transparency (EIT) has opened up potential applications in photonic technologies such as information encoding, quantum processing, and optical switching. For traditional three-level atomic systems only allow light control within a narrow frequency range, limiting multi-channel applications. To overcome this limitation, this study focuses on multi-frequency group velocity control in a 87Rb atomic medium under the influence of an external magnetic field. By combining the semiclassical theory with analytical methods, we derive the expressions for the absorption, dispersion, and group index of a four-level atomic system. Based on these results, we investigate the influence of the magnetic field and laser parameters on the absorption, dispersion, and group index. The findings not only shed light on the mechanism for controlling multi-frequency light, but also suggest potential directions for developing flexible photonic devices that meet the future demands of multi-channel information processing. Keywords: Electromagnetically induced transparency; light group velocity; external magnetic field; four-level atomic configuration
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.
We theoretically investigate the optical response of a degenerate four-level Λ\LambdaΛ-type atomic system under the influence of an external magnetic field. The applied magnetic field lifts the degeneracy of the ground sublevels via the Zeeman effect, thereby altering the two-photon resonance conditions for electromagnetically induced transparency (EIT) formation and causing the atomic response to evolve from single-EIT to double-EIT, accompanied by shifts in the EIT positions. Such variations in the EIT positions result in corresponding changes in the dispersion and group index curves, allowing the selection of desired frequency regions for different response regimes. As a result, the system can switch between transparency and absorption, as well as between slow and fast light. These findings highlight the feasibility of controlling light propagation via magnetic field, with potential applications in optical switching and quantum information technologies.
The analytical expression for the group index in a degenerated three-level lambda-type atomic system is derived as a function of the parameters of laser fields and external magnetic field. The influence of the external magnetic field on the group index is investigated. It is shown that by changing the magnitude or sign of the external magnetic field, the transparency window with normal dispersion switches to enhanced absorption with anomalous dispersion at the line center and hence the light propagation can be converted between subluminal and superluminal modes. Full Text: PDF ReferencesR. W. Boyd, "Slow and fast light: fundamentals and applications", J. Mod. Opt. 56 (2009) 1908-1915 CrossRef K.J. Boller, A. Imamoglu, S.E. Harris, "Observation of electromagnetically induced transparency", Phys. Rev. Lett. 66 (1991) 2593. CrossRef A. Lezama, S. Barreiro, and A. M. Akulshin, "Electromagnetically induced absorption", Phys. Rev. A 59 (1999) 4732-4735. CrossRef L. V. Hau, S. E. Harris, Z. Dutton, C. H. Bejroozi, "Light speed reduction to 17 metres per second in an ultracold atomic gas", Nature 397, 594 (1999) CrossRef L. J. Wang, A. Kuzmich, and A. Dogariu, "Gain-assisted superluminal light propagation", Nature 406 (6793), 277-279 (2000) CrossRef A. V. Turukhin, V. S. Sudarshanam, M. S. Shahriar, J. A. Musser, B. S. Ham, P. R. Hammer, "Observation of Ultraslow and Stored Light Pulses in a Solid", Phys. Rev. Lett. 88, 023602 (2002). CrossRef K. Bencheikh, E. Baldit, S. Briaudeau, P. Monnier, J. A. Levenson, and G. Mélin, "Slow light propagation in a ring erbium-doped fiber", Opt. Express 18 (25), 25642-25648 (2010). CrossRef E. E. Mikhailov, V. A. Sautenkov, I. Novikova, G. R. Welch, "Large negative and positive delay of optical pulses in coherently prepared dense Rb vapor with buffer gas", Phys. Rev. A 69, 063808 (2004). CrossRef E. E. Mikhailov, V. A. Sautenkov, Y. V. Rostovtsev, G.R. Welch, "Absorption resonance and large negative delay in rubidium vapor with a buffer gas", J. Opt. Soc. Am. B 21, 425 (2004). CrossRef A. M Akulshin and R. J McLean, "Fast light in atomic media", J. Opt. 12 (2010) 104001. CrossRef Vineet Bharti, Vasant Natarajan, "Sub- and super-luminal light propagation using a Rydberg state", Opt. Comm. 392 (2017) 180-184. CrossRef N.T. Anh, L.V. Doai, D.H. Son, and N.H. Bang, "Manipulating multi-frequency light in a five-level cascade EIT medium under Doppler broadening", Optik 171 (2018) 721-727. CrossRef N.T. Anh, L.V. Doai, and N.H. Bang, "Manipulating multi-frequency light in a five-level cascade-type atomic medium associated with giant self-Kerr nonlinearity", J. Opt. Soc. Am. B 35 (2018) 1233. CrossRef N.H. Bang, L.N.M. Anh, N.T. Dung and L.V. Doai, "Comparative Study of Light Manipulation in Three-Level Systems Via Spontaneously Generated Coherence and Relative Phase of Laser Fields*", Commun. Theor. Phys. 71 (2019) 947-954. CrossRef L.V. Doai, "The effect of giant Kerr nonlinearity on group velocity in a six-level inverted-Y atomic system", Physica Scripta 95 (2020) 035104 (7pp). CrossRef P. Kaur and A. Wasan, "Effect of magnetic field on the optical properties of an inhomogeneously broadened multilevel Λ-system in Rb vapor", Eur. Phys. J. D 71 (2017) 78. CrossRef H. Cheng, H. -M. Wang, S. -S. Zhang, P. -P. Xin, J. Luo and H. -P. Liu, "Electromagnetically induced transparency of 87Rb in a buffer gas cell with magnetic field", J. Phys. B: At. Mol. Opt. Phys. 50 (2017) 095401. CrossRef C. Mishra, A. Chakraborty, A. Srivastava, S. K. Tiwari, S. P. Ram, V. B. Tiwari and S. R. Mishr, "lectromagnetically induced transparency in Λ-systems of 87Rb atom in magnetic field", J. Mod. Opt. 65 (2018) 2269-2277. CrossRef S. H. Asadpour, H. R. Hamedi and H. R. Soleimani, "Slow light propagation and bistable switching in a graphene under an external magnetic field", Laser Phys. Lett. 12 (2015) 045202. CrossRef R. Karimi, S. H. Asadpour, S. Batebi and h. R. Soleimani, "Manipulation of pulse propagation in a four-level quantum system via an elliptically polarized light in the presence of external magnetic field", Mod. Phys. Lett. B 29 (2015) 1550185. CrossRef
In this work, we analytically investigate the optical response including absorption, dispersion, and group index of a six-level atomic system under electromagnetically induced transparency (EIT). A key advantage of this configuration is its ability to simultaneously generate four transparency windows at distinct frequency regions using only two controlling laser fields. The analytical model is applied to both 87 Rb and 85 Rb atoms in cold and hot conditions, enabling exploration under various experimental environments. The results provide a comprehensive picture of the fundamental optical properties of 87 Rb and 85 Rb atomic systems with the six-level configuration, offering useful insights for experimental predictions and potential applications.
We have shown that quantum interference in a driven quasi-degenerate two-level atomic system can be controlled by an externally applied magnetic field. We demonstrate that the mechanism of optical control is based on quantum interference, which allows one to implement both electromagnetically induced transparency and electromagnetically induced absorption in one atomic system. Dispersion of such the medium allows one to control group velocity of propagation of light pulses be ultra-slow or superluminal via applied magnetic field.
In the present work, a theoretical and experimental study to enhance electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) signals in an 85 R b atomic vapor medium at room temperature is conducted. Also, switching from EIT to EIA signal at a particular value of the magnetic field is observed. Further, by using circularly polarized coupling light, the dispersion profile of the linearly polarized probe signal is investigated theoretically and experimentally. The nine-level system of 85 R b D2 transition in a ladder-type configuration is fully solved by using the density matrix theory. The simulated results are found in good qualitative agreement with experimental observations. Hence, an experimental setup is developed for (1) achieving enhanced EIT and EIA signal, (2) switching from EIT to EIA, and (3) dispersion measurement. These observations have potential applications towards measurement of the group velocity of light, quantum memory, quantum information, and optical switching.