Effects Of Temperature And Interface On Optical Bistability In Granular Composites

The effects of temperature and interface on optical bistability of the macroscopic inhomogeneous granular composite are investigated in this paper. Firstly, we study the influence of temperature on linear and weak nonlinear response of metal-dielectric granular composite. We analyze the relations between the effective optical response and temperature by considering the plasma frequency and the resonant frequency which depend on the change of temperature. Within MG and BR models, we discuss n and k with increasing temperature. Our results show that as the temperature increases, the real and imaginary part of the dielectric constant of the metal particles decreases and increases respectively, and the 3-order nonlinear effective response decreases. When ωapproach plasma frequency, the temperature effect is obviously, and n and k changes differently for different microstructures when temperature changes. Secondly, based on spectral representation theory and self-consistent mean field approximation, we study temperature effect on optical bistability of metal-dielectric granular composite under strong external field in the dilute limit by in MG model. The numberical result show that the nonlinear response decreases, and bistability width become smaller, the nonlinear response is enhanced and the threshold decreases. In bistability region, both n and k has two values which increases and decreases respectively with the increasing temperature. Thirdly, we investigate temperature effect on optical bistability of two-component system, in which the granular randomly embedded in the host matrix. We numerically demonstrate that both incident frequency and volume fraction effects the bistability structure. The intensity of external applied field of bistability goes down as the volume fraction reduces. OB could be observed only when f is samller than the critical value fc which depends on incident frequency. These's little difference on bistability between MG model and BR model in the dilute limit. Both intensity of external applied field and threshold width corresponding bistability decrease as volume fraction. becomes larger. Furthermore, the upper threshold intensity decrease at high temperature. Finally, the effective nonlinear response and bistability of a two-dimensional three-component system is studied by considering the interfacial layer between the granulae and the surrounding medium. We emphasize the effects of the interfacial parameter on the effective nonlinear responses and OB behavior .It is shown that there is a a critical one λc. The effective nonlinear responses are strongly enhanced near λc and the OB behavior can be observed only whenλis smaller than λc. The threshold intensity is reduce as well as the width of OB region. In addition, the composite medium with dielectric loss is also discussed.