Optical Multistability Research Articles

Analyzing the effect of higher order nonlinearity on dispersion relation and optical multistability generation in oppositely directed coupler

We report the influence of higher order nonlinearity on dispersion relation and multistability in oppositely directed coupler with negative index material channel. The study shows that the high intensity electric field shifts the photonic bandgap down in energy. When the positive index material channel of the coupler is influenced by quintic nonlinearity the group velocity of upper branch of dispersion curve (δ–q curve) falls to zero in positive q region and the loop in the lower branch shifts to positive q region. But the minima in upper branch and loop in the lower branch are observed at negative q region when the negative index material channel is influenced by χ(5) nonlinearity. As the curvature of the dispersion relation determines the group velocity dispersion the study report the possibility for dispersion engineering in oppositely directed coupler. Also we observed that the quintic nonlinearity enhances formation of multi stable states.

Optical bistability and multistability via both coherent and incoherent fields in a three-level system

We have investigated the optical bistability and multistability behaviors in a three-level V-type system via both coherent and incoherent fields inside a unidirectional ring cavity. We find that the appearance and disappearance of optical bistability (OB)/optical multistability (OM) can easily be controlled by adjusting systemic parameters. Our scheme opens up a new possibility for realizing transition from OB to OM or vice versa for potential applications in information networks and processing with increased capacity.

Enhanced nonlinear optical response of core–shell graphene-wrapped spherical nanoparticles

We study the nonlinear optical response of graphene in nanostructures. The spherical nanoparticle coated with a monolayer of graphene displays enhanced optical Kerr nonlinearity and, consequently, optical bistability and multistability in a broad range of incident optical intensity. This optical bistability significantly appertains on the geometry of the shell-coated nanoparticle, the fractional volume of the metallic core, as well as the core genre and Fermi energy of graphene. In particular, Fermi energy could also affect the optical bistability and induce switching from optical bistability to optical multistability. Due to the importance of core–shell nanoparticles, this model may find potential applications in optical bistable devices such as all-optical switches, optical transistors, and memories.

Terahertz optical bistability of graphene-coated cylindrical core\u2013shell nanoparticles

In this study, we investigate the optical bistability of graphene-coated nanoparticles with cylindrical core–shell structure at terahertz frequency, because graphene displays optical bistability and multistability in a broad range of incident optical intensity. The choice of core–shell system is due to its larger local electric field enhancement, where this characteristic is important for the optical bistable systems. This optical bistability strongly depends on the geometry of the nanoparticle, the fractional volume of the metallic core as well as Fermi energy of graphene. The surrounding medium could also finely affect the optical bistability and induce switching from optical bistability to optical tristability. Since the prosperity of optoelectronics properties of graphene and the importance of core–shell nanoparticles have attracted enormous interest, this model may find potential applications in optical bistable devices such as all-optical switches and biosensors at terahertz communication in near future.

Incoherent control of optical bistability and multistability in a hybrid system: Metallic nanoparticle-quantum dot nanostructure

We discuss the optical bistability and multistability properties of incident light on a unidirectional ring cavity consisting of a hybrid semiconductor quantum dot-metal nanoparticle system driven by coupling and incoherent pumping fields. We consider the quantum dot system as a three-level V-type configuration which is placed near the metallic nanoparticle. We realize that the threshold of optical bistability and optical multistability can be controlled by tuning the center-to-center distance between quantum dots and metallic nanoparticles. Moreover, the effect of incoherent pumping field on optical bistability and optical multistability has been discussed for different distances between quantum dots and metallic nanoparticles.

Optical multistability generation via cavity series

We investigated a different approach to establish an optical multistability (OM) in quantum atomic systems. It is demonstrated that using two cavities in series configuration leads to a more flexible OM. The number of output intensities can be further than usual and each branch of OM diagram is controllable. In addition, we have specified necessary conditions to achieve this flexible OM. It is shown that the OM threshold and even the lengths of branches are adjustable.

Double-cavity optical bistability and all-optical switching in four-level N-type atomic system

We analyze the absorptive and hybrid absorptive–dispersive double-cavity optical bistability behavior in a four-level N-type atomic system driven by two optical fields circulating inside two independently unidirectional ring cavities and a trigger field outside the cavities. In this system, the two-photon absorption and cross Kerr nonlinearity play significant roles in the formation of bistability and can be controlled efficiently due to the quantum interference effect, and then the resulting nonlinear behavior exhibits different features from the two/three-level schemes. It is shown that the threshold values and hysteresis cycle width of the bistable curve can be manipulated via the adjustment of the system parameters. Meanwhile, we also obtain double-beam optical multistability. When adding positive and negative pulses to the cavity input, all-optical steady-state switching for the two cavity outputs can be achieved simultaneously. Therefore, the proposed scheme may have potential applications in all-optical communication and computing.

Controllable transition between optical bistability and multistability in graphene/dielectric/graphene structure

We theoretically investigated the controllable transition between optical bistability and multistability in graphene/dielectric/graphene structure for TE and TM polarizations. We show such a transition strongly depends on the Fermi energy of graphene, and thus, it can be controlled by adjusting the gate voltage applied on the graphene. In addition, we also show that the transition can be tuned by changing the thickness and permittivity of the dielectric layer, or by varying the wavelength and the incident angle of the input light. Furthermore, three S-type curves appear in our studied structure, which result in quadristability. Our results may find potential applications in optoelectronic devices.

A convenient method for controlling transformation between optical bistability and multistability

We propose a convenient method to manipulate the behavior of optical bistability (OB) and optical multistability (OM) in a double Λ-type atomic system with hyperfine structure driven by a π-polarized probe field and a σ-polarized elliptically polarized field (EPF). In the scheme, the frequency detuning of two circularly polarized components of the EPF are determined by an applied magnetic field, and the amplitudes and the phase difference of that can be modulated by rotating a quarter-wave plate, which can be used to optimize quantum interference. Our numerical results show that not only the appearance and disappearance of OB can be transformed reciprocally, but also the switch from OB to OM or vice can be easily realized only by adjusting the magnetic field B or rotating the angle ϕ with the 1/4 wave plate.

Multistability and switching in oppositely-directed saturated coupler

We investigate theoretically the optical multistability that takes place in a two-core oppositely-directed saturated coupler (ODSC) having negative index material (NIM) channel. The dynamics are studied using the Lagrangian variational method, and analytical solutions are constructed with Jacobi elliptic functions. The ODSC exhibits a bandgap as a consequence of the effective feedback mechanism due to the opposite directionality of the phase velocity and the Poynting vector in the NIM channel. Depending on the strength of the nonlinear saturation, the system admits multiple stable states. Considering the additional degrees of design freedom with respect to conventional nonlinear couplers, the ODSC could become an attractive choice for all-optical switching. The existence of multiple transmission resonance windows could also facilitate the realization of gap solitons.

A Novel Phase Sensitive Quantum Well Nanostructure Scheme for Controlling Optical Bistability

A novel four-level lambda-type quantum well (QW) nanostructure is proposed based on phase sensitive optical bistability (OB) and multistability (OM) with a closed-loop configuration. The influence of controlling parameters of the system on OB and OM is investigated. In particular, it is found that the OB behavior is strongly sensitive to the relative phase of applied fields. It is also shown that under certain parametric conditions, the OB can be switched to OM or vice versa. The controllability of OB/OM in such a QW nanostructure may bring some new possibilities for technological applications in solid-state quantum information science and optoelectronics.

Measuring the size and complex refractive index of an aqueous aerosol particle using electromagnetic heating and cavity-enhanced Raman scattering.

A quantitative understanding of light scattering by small homogeneous particles requires accurate knowledge of particle geometry and complex refractive index, m = n + ik. In weakly absorbing particles, k can be on the order of 10-9, which is well below the detection limit of almost all light scattering based instruments. Here, we describe a dual-beam optical trap that can simultaneously determine n, k, and the radius, s, of weakly absorbing aerosol particles. We utilize cavity-enhanced Raman scattering to determine n and s and electromagnetic heating from the trapping laser itself to determine k. The relationship between particle size, the trapping cell conditions, the parameters of the trapping laser, and electromagnetic heating is thoroughly discussed and it is shown that the proper choice of a light scattering model is necessary to retrieve accurate values of k when fitting measurements. The phenomenon of optical multistability and its connection to thermal locking and thermal jumping is investigated through both modeling and measurements as understanding this behavior is essential when interpreting results from electromagnetic heating experiments. Measurements are made on three different atmospheric aerosol model systems and k as low as 5.91 × 10-9 are found.

Optical response of two coupled optomechanical systems in the presence of nonlinear mediums

In this paper, we investigate response of a hybrid optomechanical system in different situations. This system is composed of two coupled optomechanical cavities, which one of them is filled with an optical parametric amplifier (OPA) and the other one encompasses a nonlinear Kerr medium. The Hamiltonian of the system is written in a rotating frame. The dynamics of the system is obtained by the quantum Langevin equations of motion in a steady state regime. The results show that the presence of OPA and the Kerr medium in the system can considerably change the behavior of both cavities. For this reason, we show that by choosing different values for the optical parameters of the system, one can switches the behaviors of the cavities between mono-, bi- and tristability. Also, we show that by changing the detunings of the cavities, one can obtain uncommon responses from the system. Furthermore, we show that it is possible to create proper optical multistability regions for both cavities.

Optical multistability in 1D photonic crystal doped with carbon-nanotube quantum dot nanostructures

The optical bistability (OB) and multistability (OM) in one-dimensional photonic crystals doped with carbon-nanotube quantum dots (CNT QDs) is theoretically investigated. Our investigations show that due to spin–orbit coupling in CNT QDs the threshold of optical bistability can be adjusted. Also, the switching from OB to OM, or vice versa, can be achieved by controlling the transverse magnetic field. Our proposed model can be used as a suitable structure based on CNT QDs for realizing all-optical switching devices. Moreover, we realize that the controlling of OB and OM can be done without changing the thickness of the layers.

Optical bistability forming due to a Rydberg state

We consider the behavior of optical bistability (OB) and multistability (OM) in a four-level atomic system involving a Rydberg state illuminated by a probe field as well as control and switching laser beams of larger intensity. When the switching field is absent, no OB arises because of the effect of Rydberg electromagnetically induced transparency. However, by application of the switching field, the hysteresis cycle appears to give rise to optical bistability, thanks to Rydberg electromagnetically induced absorption. It is further demonstrated that one can efficiently modify the OB threshold via suitable choices of system-controlling parameters. Interestingly, it is observed that this model can produce an optical switching between OB and OM with potential applications in logic-gate devices for optical communication.

Multiple spontaneously generated coherence and phase control of optical bistability and multistability in a tripod four-level atomic medium.

Optical bistability (OB) and optical multistability (OM) behaviors induced by multiple spontaneously generated coherence (SGC) are investigated theoretically in a tripod four-level atomic scheme. It is found that OB or OM is sensitive to the SGC effects, and the thresholds of OB can be controlled via changing the strength of multiple SGC or the relative phases of the applied fields. In addition, we can switch OB to OM by adjusting the twofold relative phases of the applied fields or vice versa.

Toggle switch from optical bistability to multistability via an elliptically polarized field

In this paper, we propose a scheme for manipulating the behavior of optical bistability (OB) and optical multistability (OM) in an N-type four-level atomic system. In the scheme, quantum interference is optimized by the left-handed and the right-handed fields of an elliptically polarized field (EPF). The threshold and the hysteresis cycle shape of OB and OM can be controlled by modulating the intensity of the EPF. Especially, the transition from OB to OM or vice versa can also be easily realized by proper tuning the phase difference between the left-handed and right-handed polarized fields under the optimal intensity of the EPF.

Tunable Optical Bistability and Tristability in Nonlinear Graphene-Wrapped Nanospheres

We develop the nonlinear electromagnetic theory (NET) including the self-consistent mean-field approach to investigate the optical multistability of graphene-wrapped dielectric nanoparticles. We demonstrate the optical bistability (OB) of the graphene-wrapped nanoparticle in both near-field and far-field spectra due to electric dipolar modes for small sizes, as predicted in the quasistatic limit (QL). For small sizes, two OB regions can be observed when the magnetic dipolar modes arise under the strong field. On the other hand, for large sizes, one observes the optical tristability (OT) and even optical multistability arising from the contributions of higher-order magnetic modes. Furthermore, both the optically stable region and the switching threshold values can be tuned by changing either the Fermi level or the size of the nanoparticles. Our results show promise for the graphene-wrapped dielectric nanoparticle as a candidate for multistate optical switching, optical memories, and relevant optoelectronic...

Optical multistability in double quantum dot system: Effect of momentum matrix elements

Optical stability behavior in a unidirectional ring cavity containing a ladder-plus-Y double QD (DQD) structure was modeled in this work using the density matrix theory in parallel with Momentum matrix elements including interdot QD-QD transitions. QD-WL transitions, which were not included in any other bistability work in QD structures, are also modeled here. Pumping optical field reduces the threshold of optical bistability (OB). The coupling field, which dressing DQD states and strengthens Kerr nonlinearity are increased.It is shown that optical multistability (OM) was the figure of merit for the stability behavior in DQD system, in the contrary with other researches, as a result from considering the calculation of all transition momenta, here. Additionally, considering QD-WL transition reduces OM threshold.

Bistable Beam Propagation in Liquid Crystals

Light-controlling-light is one of the most advanced paradigms in optical signal processing, including light-induced waveguides as well as all-optical switching and routing. Other fundamental aspects of all-optical processing are optical memories and sequential elements, which require responses depending on the evolution history of the system, such as the hysteresis stemming from optical multistability. Hereby, we report on optical bistability and hysteresis in cavityless geometries and in the presence of self-localized beams, i.e., spatial optical solitons, exploiting the nonlocal reorientational nonlinearity of nematic liquid crystals (NLC). When the optic axis of NLC is initially orthogonal to the applied electric field, the molecular dipoles start to rotate above a threshold named after the Freedericksz transition, the latter being usually of the second order. Here, we show that such transition become of the first order via the intrinsic feedback provided by self-focusing, in turn leading to the appearance of a hysteresis loop between diffracting and self-confined beams. We report on hysteresis of the beam size versus input power, as well as hysteresis versus applied voltage at a fixed beam power. Our findings introduce a novel kind of cavity-less optical bistability with propagating light beams and disclose a novel approach to information storage based on light self-localization.