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VNU Journal of Science Mathematics - Physics

Controlling optical properties and optical bistability via an external magnetic field in a tripod-type atomic medium

Hoang Thi Huong, Le Nguyen Mai Anh, Le Thi Hoa Lai, Le Thanh Hoa, Nguyen Van Phu, Thanh Thai Doan, Nguyen Tuan Anh, Hoang Minh Dong

Published May 6, 2026• 0 citations
Publisher

Abstract

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.

DOI
10.25073/2588-1124/vnumap.5115

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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.
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 numerically investigate two-channel pulse propagation dynamics in a degenerate tripod-type four-level atomic medium under the combined influence of an external magnetic field and a relative phase. The results show that an external magnetic field is used as a “knob” to switch between transparent and absorptive regimes of the probe pulse by the on/off state of the magnetic field within suitable frequency and phase domains. By tuning the magnitude of the magnetic field, the transparency spectrum can be reversibly transformed between single- and double-window structures, enabling stable pulse propagation in a single- or dual-channel. In addition, the relative phase strongly modifies the probe absorption profile and provides an efficient means to control pulse propagation dynamics. These findings suggest promising applications in pulse propagation, multi-channel switching, and optical storage for communication systems.
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.
Abstract Optical properties including absorption, dispersion, group index, Kerr nonlinearity, and optical bistability of a three-level V-type atomic medium have modified by varying an external magnetic field. By changing the magnitude or the sign of the external magnetic field, the transparency window with normal dispersion transfers to the enhanced absorption with anomalous dispersion at the line center, and hence the light propagation switches between subluminal and superluminal modes. The magnitude and the sign of the Kerr nonlinearity are controlled with the strength and the sign of the magnetic field. As a consequence, the behaviors of optical bistability are also made to appear or disappear when switching on/off the magnetic field. Moreover, the threshold intensity and width of optical bistability are also changed by the magnetic field and the coupling field. The results can be used to control the working characteristics of applied devices and study the related effects.