光学双稳态的阈值取决于非线性材料中的场局域程度,场局域越强,阈值越低.而材料的损耗是影响场局域强弱的重要因素.之前,人们普遍认为,增加损耗会削弱场局域,不利于降低阈值.本文研究了由磁单负材料和电单负材料组成的异质结构中光学双稳态现象,发现随着损耗的增大,其阈值可以呈现先降后升的非单调变化.进一步研究表明,异质结构界面处的电磁场强度随着损耗增大呈现先降后升的非单调变化,即增加损耗也有可能增强场局域.研究结果揭示了场局域程度与材料损耗之间的非单调依赖关系,为设计开发非线性功能器件提供了新的思路.
Permittivity depends on the electric field intensity in a nonlinear material,and it changes with the incident intensity of the electromagnetic wave.This phenomenon leads to the occurrence of optical bistability.The optical bistable threshold value depends on the localized degree of electromagnetic field in the nonlinear material,and the stronger the localized field,the lower the threshold value is.However,the loss of material is one of the important factors influencing the strength of the local field.It is commonly believed that the loss is not conducible to reducing the threshold value because increased loss can weaken the localized degree of fields.For the lossy single-negative metamaterial,the transmission is nonmonotonic as the loss varies.That is to say,the transmission first decreases and then increases in the lossy single-negative metamaterial.Therefore,the nonlinear transmission in the lossy single-negative metamaterial may lead to novel physical phenomena.Permeability-negative material and permittivity-negative material are two kinds of different single-negative metamaterials.In this paper,the optical bistable phenomena in the heterostructure of permeability-negative material and permittivity-negative material are studied by using the transfer matrix method.Here,the permittivity-negative material is nonlinear material.The results show that the optical bistable threshold value first increases and then falls down as the loss increases.The variance of the localized electromagnetic field at the interface between the permeability-negative layer and the permittivity-negative layer at the discussed frequency is discussed in the present paper to understand the nonmonotonic phenomenon.Further studies indicate that the nonmonotonic localized electromagnetic field is also presented at the interface between the permeability-negative layer and permittivity-negative layer.That is to say,the enhancement of the localized field can be obtained when the loss is increased,which results in the nonmonotonic optical bistable