Possibility of generating negative refractive index in a multilevel atomic medium interacting with four electromagnetic fields is discussed. The spontaneously generated coherence arising due to the nearby decaying levels produces such negative refractive index.
A new mechanism for realizing negative refractive index with a four-level atomic system is suggested. The explicit expressions for the electric permittivity and magnetic permeability at probe frequency are presented. It is shown that there is a frequency band in which the four-level photonic-resonant atomic vapour may exhibit simultaneously negative permittivity and permeability, and that such an atomic vapour may become a left-handed material (negatively refracting medium). Compared with the previous schemes to realize negative refraction within the framework of classical electromagnetic theory, the most remarkable features of the present scenario are as follows: (i) isotropic material with microscopic structure units at atomic-scale level, (ii) negative refraction in visible and infrared frequency bands, (iii) controllable manipulation by external fields and (iv) based on quantum coherence in a multilevel atomic system.
We propose a scheme for realizing negative refractive index in a V-type four-level atomic system. It is shown that the negative refractive index can be achieved in a wide frequency band based on the effect of quantum coherence. It is also found that the frequency band of negative refractive index and the absorption property of left-handed material are manipulated by the pump and control fields. Furthermore, left-handed material with reduced absorption is possible by choosing appropriate parameters. (c) 2006 Elsevier B.V. All rights reserved.
We propose a scheme for realizing negative refractive index in a multilevel atomic system. The theoretical modeling has been done using density matrix approach in which the spontaneously generated coherence (SGC) is also induced. It is shown that the negative refractive index can be obtained on the effect of quantum coherence. The parameters () quantifying left-handedness in the system become more negative if the SGC is defined in the appropriate value. Furthermore, left-handed material with reduced absorption is possible by choosing appropriate parameters.
In this work, we study the generation of a negative refractive index based on electromagnetically induced transparency (EIT) in a Rb four-level N-type atomic gas medium. We derive analytic expressions for the relative permittivity and relative permeability of the medium according to the parameters of the probe, pump, and signal laser fields. We then investigate the variation of the real parts of the relative permittivity and relative permeability with respect to the intensity and frequency of the pump and signal laser fields. In the presence of the pump laser beam, the medium becomes transparent to the probe laser beam even in the resonant region. At the same time, the real parts of the relative permittivity and relative permeability are simultaneously negative (i.e., the medium exhibits a negative refractive index) in the EIT spectral domain. In the presence of the signal laser beam, the EIT effect occurs over two different frequency domains of the probe beam, so a negative refractive index is also generated in these two frequency domains. The investigation of the real parts of the relative permittivity and relative permeability with intensity and frequency of the pump and signal laser fields allowed us to find the laser parameters for the appearance of the negative refractive index, which can be useful for experimental observations.
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.
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.