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Dalat University Journal of Science

OPTICAL BISTABILITY IN A DEGENERATE TWO-LEVEL EIT MEDIUM UNDER THE INFLUENCE OF AN EXTERNAL MAGNETIC FIELD: AN ANALYTICAL APPROACH

Le Thi Minh Phuong, Dinh Xuan Khoa, Nguyen Huy Bang, Thai Doan Thanh, Nguyễn Tuấn Anh, Nguyen Thi Thu Hien, Hoang Minh Dong

Published Jul 22, 2021• 1 citation
Publisher

Abstract

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.

DOI
10.37569/dalatuniversity.11.4.872(2021)

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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.
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 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.
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.
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 In this paper, a novel degenerate two-level model is proposed to study the behavior of optical bistability (OB) and optical multistability (OM) under the effect of the magnetic field and relative phase. We show that the behavior of the OB can appear in the resonant regime by changing the strength of the external magnetic field. Especially, the result has shown that it is possible to easily convert between OB and OM by adjusting the strength of the external magnetic field or coupling field in the presence of the relative phase. In addition, the influence of the probe detuning and the atomic cooperation parameter on the OB behavior have also been considered. The studied results may be helpful for optical communication applications in optical switching processing and optimization.
We propose an optical bistability (OB) model consisting of a five-level cascade electromagnetically induced transparency (EIT) medium placed in a unidirectional ring cavity. An input-output intensity relationship for a weak probe light field is derived as a function of parameters of a strong coupling light and cooperation C. The OB behaviors of the system are investigated with variation of the parameters. It has been shown that the OB behaviors occur simultaneously in three EIT windows. Furthermore, switching thresholds and the hysteresis loop can be controlled by the parameters of the coupling light and/or a cooperation of atomic medium. Such controllable OB behaviors can find interesting applications in bistable photonic devices working at low light intensity and multiple frequencies.