The Experts below are selected from a list of 192 Experts worldwide ranked by ideXlab platform
Lei Gao - One of the best experts on this subject based on the ideXlab platform.
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Low-threshold Optical Bistability of graphene-wrapped dielectric composite.
Scientific reports, 2016Co-Authors: Yang Huang, Andrey E. Miroshnichenko, Lei GaoAbstract:We theoretically study the effective third-order nonlinear response and Optical Bistability of the 3D graphene based composite consisting of graphene wrapped dielectric nanoparticles embedded in dielectric host at terahertz frequencies. Taking into account the nonlinear conductivity of graphene, we derive the analytical expressions for the effective third-order nonlinear coefficient χe3 in weakly nonlinear limit. Moreover, for strong applied fields, the criterion for achieving Optical Bistability in such a graphene coated sphere, as well as the switching thresholds of Optical Bistability are discussed. We find that both χe3 and Optical Bistability are strongly dependent on the Fermi energy of graphene and it is possible to achieve very low switching thresholds under the normal graphene dissipation. We further propose a scheme to study the transmittance of this nonlinear composite slab. These results reveal novel regime of the Optical Bistability of the transmittance of light. We show that this kind of graphene-wrapped composite, which has tunable and low threshold Optical Bistability, can be the best candidate for unique nonlinear Optical materials.
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Optical Bistability in a nonlinear-shell-coated metallic nanoparticle.
Scientific reports, 2016Co-Authors: Hongli Chen, Youming Zhang, Baile Zhang, Lei GaoAbstract:We provide a self-consistent mean field approximation in the framework of Mie scattering theory to study the Optical Bistability of a metallic nanoparticle coated with a nonlinear shell. We demonstrate that the nanoparticle coated with a weakly nonlinear shell exhibits Optical Bistability in a broad range of incident Optical intensity. This Optical Bistability critically relies on the geometry of the shell-coated nanoparticle, especially the fractional volume of the metallic core. The incident wavelength can also affect the Optical Bistability. Through an optimization-like process, we find a design with broader bistable region and lower threshold field by adjusting the size of the nonlinear shell, the fractional volume of the metallic core, and the incident wavelength. These results may find potential applications in Optical bistable devices such as all-Optical switches, Optical transistors and Optical memories.
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Optical Bistability in composite media with nonlinear coated inclusions
Physics Letters A, 2003Co-Authors: Lei GaoAbstract:We study the intrinsic Optical Bistability in nonlinear composites of coated spherical particles with a metallic core and a nonlinear dielectric shell. By means of self-consistent mean field approximation, the relation between the local field in the core of inclusions and the external applied field is established. We demonstrate numerically that the Optical Bistability exists only when the interfacial parameter λ is less than a critical one λc. By the suitable adjustment of λ in the range (0,λc), the threshold fields can be reduced substantially, and thus improve the potential applicability of this kind of material. The dielectric loss is found to reduce the Optical Bistability region due to the increase in the lower threshold field. Furthermore, the reflectance at normal incidence R is calculated, and the hysteresis loops are found also.
Dianyuan Fan - One of the best experts on this subject based on the ideXlab platform.
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low threshold Optical Bistability in one dimensional gratings based on graphene plasmonics
Optics Express, 2017Co-Authors: Jun Guo, Leyong Jiang, Yue Jia, Xiaoyu Dai, Yuanjiang Xiang, Dianyuan FanAbstract:Optical Bistability of graphene surface plasmon is investigated numerically, using grating coupling method at normal light incidence. The linear surface plasmon resonance is strongly dependent on Femi-level of graphene, hence it can be tuned in a large wavelength range. Due to the field enhancement of graphene surface plasmon resonance and large third-order nonlinear response of graphene, a low-threshold Optical hysteresis has been observed. The threshold value with 20MW/cm2 and response time with 1.7ps have been verified. Especially, it is found that this Optical Bistability phenomenon is angular insensitivity for near 15° incident angle. The threshold of Optical Bistability can be further lowered to 0.5MW/cm2 by using graphene nanoribbons, and the response time is also shorten to 800fs. We believe that our results will find potential applications in bistable devices and all-Optical switching from mid-IR to THz range.
Seyyed Hossein Asadpour - One of the best experts on this subject based on the ideXlab platform.
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Managing Optical Bistability and multistability by embedding quantum dot nanostructures in a photonic crystal
The European Physical Journal Plus, 2016Co-Authors: Seyyed Hossein Asadpour, Gh. Solookinejad, M. Panahi, E. Ahmadi SangachinAbstract:The Optical Bistability and multistability properties are studied in a defect slab doped with acceptor and donor quantum dots embedded in a nonlinear photonic crystal. It is shown that the intensity threshold of Optical Bistability can be controlled via the corresponding controllable parameters, such as Rabi frequency of coupling field and the thickness of the slab. It is found that the switching from Optical Bistability to multistability can be obtained by enhancing the Rabi frequency of the coupling field. Moreover, it is observed that the dipole-dipole interaction between acceptor and donor quantum dots can lead to modifying the behaviors of Optical Bistability and multistability. Also, it is demonstrated that the Optical thickness of the slab can be used as a potential parameter to control the intensity threshold of Optical Bistability and multistability. It is found that, by decreasing or increasing the Optical thickness parameter, the threshold of Optical Bistability or multistability can be decreased or increased, correspondingly. We hope that our proposed model can be used for developing the future all-Optical systems based on photonic materials doped with nanoparticles.
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Polarization dependence of Optical Bistability in the presence of external magnetic field
Optics Communications, 2014Co-Authors: Seyyed Hossein Asadpour, Hamid Rahimpour SoleimaniAbstract:Abstract In this paper, a four-level inverted Y type atomic system for controlling the Optical Bistability and multistability is proposed. An elliptically polarized probe field and a coherent coupling field in the presence of external magnetic field are interacted by this medium. It is shown that the external magnetic field and relative phase between two electric field components of the probe field can influence the threshold of Optical Bistability. Moreover, it is found that Optical Bistability can be converted to the Optical multistability by external magnetic field and relative phase.
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Optical Bistability and multi-stability in a four-level atomic scheme
Optical and Quantum Electronics, 2012Co-Authors: Hamid Reza Hamedi, Seyyed Hossein Asadpour, Mostafa Sahrai, Behnam Arzhang, D. TaherkhaniAbstract:We investigate the Optical Bistability (OB) and Optical multi-stability (OM) in a four-level Y-type atomic system. It is found that the Optical Bistability can strongly be affected by intensity and frequency detuning of coupling and probe fields. The effect of spontaneously generated coherence on phase control of the OB and OM is then discussed. It has also been shown that the Optical Bistability can be switched to Optical multi-stability just by the quantum interference mechanism and relative phase of applied fields.
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controlling the Optical Bistability and transmission coefficient in a four level atomic medium
Journal of Luminescence, 2012Co-Authors: Seyyed Hossein Asadpour, Abdullah EslamimajdAbstract:Abstract A novel four level atomic configuration is proposed for controlling the Optical Bistability and transmission coefficient 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 has derived another atomic transition. 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 magnitude of the external magnetic field. Also, it is shown that Optical Bistability can be converted to Optical multistability by switching the two orthogonally polarized beams.
Govind P Agrawal - One of the best experts on this subject based on the ideXlab platform.
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analytical study of Optical Bistability in silicon ring resonators
Optics Letters, 2010Co-Authors: Ivan D Rukhlenko, Malin Premaratne, Govind P AgrawalAbstract:We analyze theoretically the nonlinear phenomenon of Optical Bistability inside a ring resonator formed with a silicon-waveguide nanowire and derive an exact parametric relation connecting the output intensity to the input intensity. Our input-output relation accounts for linear losses, the Kerr nonlinearity, two-photon absorption, free-carrier-induced absorption and dispersion, and thermo-optic effects within the resonator. Based on our study, we generalize the standard definition of effective length to allow for all possible losses within a silicon ring resonator. We also present a simplified version of the bistable phenomenon valid for resonators operating in a regime in which losses resulting from two-photon absorption are relatively small. Our analytical results provide clear insight into the physics behind Optical Bistability and may be useful for designing silicon-based Optical memories.
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analytical study of Optical Bistability in silicon waveguide resonators
Optics Express, 2009Co-Authors: Ivan D Rukhlenko, Malin Premaratne, Govind P AgrawalAbstract:We present a theoretical model that describes accurately the nonlinear phenomenon of Optical Bistability in silicon-waveguide resonators but remains amenable to analytical results. Using this model, we derive a transcendental equation governing the intensity of a continuous wave transmitted through a Fabry-Perot resonator formed using a silicon-on-insulator waveguide. This equation reveals a dual role of free carriers in the formation of Optical Bistability in silicon. First, it shows that free-carrier absorption results in a saturation of the transmitted intensity. Second, the free-carrier dispersion and the thermo-optic effect may introduce phase shifts far exceeding those resulting from the Kerr effect alone, thus enabling one to achieve Optical Bistability in ultrashort resonators that are only a few micrometers long. Bistability can occur even when waveguide facets are not coated because natural reflectivity of the silicon-air interface can provide sufficient feedback. We find that it is possible to control the input-output characteristics of silicon-based resonators by changing the free-carrier lifetime using a reverse-biased p-n junction. We show theoretically that such a technique is suitable for realization of electronically assisted Optical switching at a fixed input power and it may lead to silicon-based, nanometer-size, Optical memories.
Yang Huang - One of the best experts on this subject based on the ideXlab platform.
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Low-threshold Optical Bistability of graphene-wrapped dielectric composite.
Scientific reports, 2016Co-Authors: Yang Huang, Andrey E. Miroshnichenko, Lei GaoAbstract:We theoretically study the effective third-order nonlinear response and Optical Bistability of the 3D graphene based composite consisting of graphene wrapped dielectric nanoparticles embedded in dielectric host at terahertz frequencies. Taking into account the nonlinear conductivity of graphene, we derive the analytical expressions for the effective third-order nonlinear coefficient χe3 in weakly nonlinear limit. Moreover, for strong applied fields, the criterion for achieving Optical Bistability in such a graphene coated sphere, as well as the switching thresholds of Optical Bistability are discussed. We find that both χe3 and Optical Bistability are strongly dependent on the Fermi energy of graphene and it is possible to achieve very low switching thresholds under the normal graphene dissipation. We further propose a scheme to study the transmittance of this nonlinear composite slab. These results reveal novel regime of the Optical Bistability of the transmittance of light. We show that this kind of graphene-wrapped composite, which has tunable and low threshold Optical Bistability, can be the best candidate for unique nonlinear Optical materials.
