We propose a simple system for both optical switching and bistability based on degenerated two-level atoms placed in a ring cavity and an external magnetic field. The magnetic field splits a lower level into two separated levels, both of which are connected to an upper level by coupling and probe laser fields. Under an electromagnetically induced transparency regime, the system exhibits optical bistability and switching properties in which its thresholds and switching rate can be controlled by modulating intensity of the magnetic field or the coupling light field. Furthermore, the system can be controlled to work in varying frequency regimes by using a sole laser for both coupling and probe fields. Such a proposed scheme may be useful for realization of optical switches and storage devices.
We propose a simple system for both optical switching and bistability based on degenerated two-level atoms placed in a ring cavity and an external magnetic field. The magnetic field splits a lower level into two separated levels, both of which are connected to an upper level by coupling and probe laser fields. Under an electromagnetically induced transparency regime, the system exhibits optical bistability and switching properties in which its thresholds and switching rate can be controlled by modulating intensity of the magnetic field or the coupling light field. Furthermore, the system can be controlled to work in varying frequency regimes by using a sole laser for both coupling and probe fields. Such a proposed scheme may be useful for realization of optical switches and storage devices.
We investigate the behavior of optical bistability in a degenerate two-level atomic medium using an external magnetic field to separate the lower level into two distinct levels that both connect to an upper level by the probe and coupling laser fields. Based on analytical solutions, the absorption spectrum and behavior of optical bistability in an electromagnetically induced transparency regime under an external magnetic field are investigated. By controlling the external magnetic field, we find that the appearance and disappearance of the optical bistability can be easily controlled according to the strength of the magnetic field in the transparent window domain. Furthermore, the effects of the intensity of the coupling laser field and the parameters of the system on the behavior of optical bistability are also considered. The proposed model is useful for applications in all-optical switches and magneto-optic storage devices.
In this paper, we study the formation of optical bistability (OB) and optical multistability (OM) in a degenerate four-level atomic system by an external magnetic field that is excited by a probe laser field, a coupling laser field and a signal laser field. The coupling field can cause electromagnetically induced transparency (EIT) for the probe field in the atomic medium, while the signal field and/or external magnetic field can switch between single-EIT and two-EIT regimes. Based on these properties, OB and OM effects can be formed at two different frequency regions of the probe field (two channels). By adjusting the magnetic field or the intensity and the frequency of laser fields, the threshold intensity and the width of OB or OM can also be changed simply. The model can be useful for experimental observations and applications in modern photonic devices.
A four-level inverse Y-type atomic system with a microwave-driven field contained in a unidirectional ring cavity is proposed for controlling the optical bistability behavior with application on all-optical switching. Two circularly polarized components from a weak linearly-polarized probe beam are interacted separately by two transitions of this medium. A coherent coupling field derived another atomic transition. Under the steady state condition, we can control the occurrence of the optical bistability by modulating different parameters, such as the probe detuning ( ), the electronic cooperation parameter (C), the magnitude of electromagnetic field (B), and left- or right- handed circular polarized beams. Also, it is found that the stable output field of the optical cavity can be controlled by adjusting the intensity of the input field. It is demonstrated that the transmission coefficient of two orthogonally polarized beams at different frequencies can be achieved by adjusting the magnitude of the external magnetic field. It is found that the threshold of the optical bistability can be controlled by the magnitude of the external magnetic field. Also, it is shown that the optical bistability can be converted to optical multistability by switching the two orthogonally polarized beams. In this paper, in the case of the steady-state and transient response, we investigated the effect of external magnetic field on optical bistability of a four-level atomic system in the presence of strong coherent laser beam. Here, a laser probe signal consists of two left- and right- handed circular polarized beams which are interacted by two different transitions. The optical system provides a new experimental method to test optical bistability theory.
We investigated control of optical bistability behavior based on the probe absorption and Kerr nonlinearity properties in a tripod-type degenerate four-level atom system under an external magnetic field. This excitation configuration can provide two transparent spectral regions on the probe absorption profile. It can be transitioned between the transparency and absorption regimes by turning on or off the magnetic field in different frequency domains. We can effortlessly transform one into two transparency windows, and vice versa, by modifying the intensity of the magnetic field. The investigations showed the enhancement of the Kerr nonlinearity around one/two-EIT windows, thereby forming one/two-channel optical bistability in these frequency regions. In addition, the coupling field intensity, the probe frequency detuning, and the atomic cooperation parameter have also significantly influenced the absorption spectrum, Kerr nonlinearity, and optical bistability. The proposed model has useful applications for storage and optical switching, and nonlinear logic gates in optical communications processing.
We study control of the Kerr nonlinearity and two-channel magneto-optical switching based on optical bistability behavior in a degenerate Y-type four-level atom system under a static magnetic field. This excitation configuration can provide two transparent spectral regions on the probe absorption profile. It can be transitioned between the transparency and absorption regimes by turning on or off the magnetic field in different frequency domains. We can effortlessly transform single- to double-transparency windows, and vice versa, by adjusting the strength/direction of the magnetic field. The investigations showed the enhancement of the Kerr nonlinearity around single/double-EIT windows, thereby creating single/two-channel optical bistability in these frequency regions. Particularly, flexible high-efficiency two-channel magneto-optical switching can be made based on optical bistability behavior with fixed cavity input at different frequency regions. Additionally, the coupling field intensity and the probe frequency detuning have also significantly influenced the absorption spectrum, Kerr nonlinearity, and optical bistability. The proposed model is a representative application for optical switching, storage, and nonlinear logic gates in optical communications.
Abstract Magnetic field plays an important role in studying the transient response because the transition probabilities of degenerate energy levels depend on the external field. The application of an external magnetic field is of particular interest, as the magnetic field is readily available and more flexible to control than an additional laser field, which is an essential consideration in our paper. In this work, we propose a simple model for managing the transient absorption and dispersion properties in a degenerate two-level atomic medium under both transparency and absorption regimes in the presence of spontaneously generated coherence (SGC), an incoherent pumping field, and an external magnetic field. We show that a magnetic field can be utilized as a ‘knob’ to swap the transient absorption and dispersion properties of the system in both transparency and absorption regimes. The magnetic field not only aids in creating transparency and absorption regimes but is also helpful in controlling the system operating at different frequency regions for the probe field without changing the frequency of the coupling field; SGC is introduced to enhance the laser phase dependence of the atomic optical properties, while the incoherent pumping field plays a role in enhancing the effects of SGC and relative phase on the atomic optical properties. The influences of SGC, relative phase, and incoherent pumping rate on transient response are also considered to improve the stability of transient absorption and dispersion properties. Moreover, the essential time required for swapping between subluminal and superluminal light propagation is also provided. The proposed model shows that the system can be used as an ultrafast optical switch, which, in practice, may enable control over switching rates in quantum storage and information-processing devices.