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Electric and Magnetic Coherences: Analysis in a Four-Level Atomic System under a Magneto-Shaped Field

Nadia Boutabba, Hazrat Ali

Published Dec 21, 2023• 0 citations
Publisher

Abstract

Abstract In this work, we investigate the dispersion-absorption spectra in a left handed medium under various magnetic shaped pulses. The system is a multi-level atom, in which the levels are coherently controlled by a weak and a strong field. Additionally, the ground state is related to an intermediate transition via a magneto-shaped field.We analyze the four level atom while first by considering the magnetic field as a quotient of the double exponential wave form, a difference of Gaussian and then as a continuous wave form. This enables us to study the dynamics of the coherence in the system. therefore, in contrast with the classical scenario where the magnetic field is taken as a constant, we observe a clear influence of the shaped magnetic field on the dispersion-absorption of the probe. We get an enhancement of about 2.5 times in the positive dispersion while we obtain 8 times enhancement in the negative dispersion. Lastly, with a shaped magnetic field, the probe dispersion, which is positive for a positive detuning and negative for a negative detuning, abruptly changes in the opposite direction.

DOI
10.21203/rs.3.rs-3767766/v1

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Abstract In this work, we investigate the dispersion-absorption spectra in a left handed medium under various magnetic shaped pulses. The system is a multi-level atom, in which the levels are coherently controlled by a weak and a strong field. Additionally, the ground state is related to an intermediate transition via a magneto-shaped field.We analyze the four level atom while first by considering the magnetic field as a quotient of the double exponential wave form, a difference of Gaussian and then as a continuous wave form. This enables us to study the dynamics of the coherence in the system. therefore, in contrast with the classical scenario where the magnetic field is taken as a constant, we observe a clear influence of the shaped magnetic field on the dispersion-absorption of the probe. We get an enhancement of about 2.5 times in the positive dispersion while we obtain 8 times enhancement in the negative dispersion. Lastly, with a shaped magnetic field, the probe dispersion, which is positive for a positive detuning and negative for a negative detuning, abruptly changes in the opposite direction.
The influence of external magnetic field and relative phase between two electric field components of the probe field on absorption–dispersion and group index of a four-level atomic system with two degenerate sublevels are investigated. The results show that, the behaviors of weak probe light can be controlled by an external magnetic field. It is shown that in the presence of the external magnetic field the additional electromagnetically induced transparency (EIT) window can be obtained. Our result also reveal that the switching from slow to fast light or vice versa can be manipulated by changing the phase difference between the two circularly polarized components of a single coherent field.
The quantum system with an interaction between a closed Y-type four-level atom and multi-mode light fields is adopted to possess left handedness by means of the technique of quantum coherence. In the representation of interaction, the density matrix method is utilized in view of the rotating-wave approximation and the di-pole approximation.The conclusion of the numerical simulation shows that under the appropriate parameter conditions, the medium can achieve negative permittivity and negative permeability simultaneously (i.e. the left handedness effect happens and the left-handed material is realized.) In the condition of the weak probe field, when the Rabi frequency of probe light increases, the frequency range of the medium to achieve its left-handed effect decreases and the refractive index and absorption coefficient will also changed correspondingly. The medium to affect light absorption and gain in the conditions of the establishment of left -handed effect are also discussed. The paper can be concluded that, in the conditions of weak probe field, the electro-magnetic induction can be used to achieve the left-handed effect of the medium, which extends the implementation of left-handed materials in the experiment, and extends the application field of electro-magnetic induction.
In this work, we investigate the atomic properties of a three-level system under the effect of a shaped microwave field. The system is simultaneously driven by a powerful laser pulse and a weak constant probe that drives the ground state to an upper level. Meanwhile, an external microwave field drives the upper state to the middle transition with shaped waveforms. Hence, two situations are considered: one in which the atomic system is controlled by a strong laser pump and a classical constant microwave field, and another in which both the microwave and pump laser fields are shaped. Finally, for sake of comparison, we investigate the tanh-hyperbolic, the Gaussian and the power of the exponential microwave form in the system. Our results reveal that shaping the external microwave field has a significant impact on the absorption and dispersion coefficient dynamics. In comparison with the classical scenario, where usually the strong pump laser is considered to have a major role in controlling the absorption spectrum, we show that shaping the microwave field leads to distinct results.
Abstract In this theoretical work, we study the optical behaviour of a microwave driven four-level tripod-type atomic system, configured by Zeeman sub-levels in D 1 line of 87 Rb atom. The non-optical microwave field (L) reasonably assists the optical pumping by a linearly polarized (π) laser field (P1) and a right-handed circularly polarized (σ +) laser field (P2), in presence as well as absence of a static magnetic field (MF). The optical responses of the system to the left-handed circularly polarized (σ −) optical probe laser field (Pr) under three specific P1-P2 strength conditions depict substantial variations in the Doppler-free and Doppler-broadened absorption peaks, accompanied with single EIT or double EIT windows. The origin of Doppler-free Pr absorption peaks are explained by analyzing the resonant poles for the scanning Pr which attribute to the decaying-dressed-states. Perceptible changes of resonant pole positions on the complex planes of the poles w. r. t. the applied MF and L signify that one can externally alter the optical responses of the medium. The related Pr dispersion and its controllability are discussed as well. It is found that the interaction length of the Doppler-free medium has a prominent effect on the Pr absorption and transmission when both MF and L are present in the medium. Furthermore, we have shown the modifications in the Doppler-free Pr absorption profiles in presence of MF and L by considering P2 as an elliptically polarized laser field. Interestingly, Pr absorption turns into Pr gain at suitable polarization rotation angles of the elliptically polarized P2 field for different P1-P2 strength ratios.
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.
We investigate the dispersion and absorption in the coherently prepared two-level degenerate systems. Driven by a parallel polarized light and probed by a transverse polarized light, in the degeneracy case, only the positive dispersion is obtained at the zero pump-probe detuning, as well as electromagnetic induced transparency. When magnetic field breaks the degeneracy, we find that the dispersion is shifted from positive, via negative, to positive when varying the drive Rabi frequency, which means a transition between the superluminal and subluminel group velocity. Simultaneously, in these systems, the electromagnetic induced transparency, electromagnetic induced absorption and Mollow absorption spectrum are shown in the absorption spectra.