Optical Tristability Research Articles

Optical switching in composite media containing nonlinear plasmonic coated particles with radial anisotropy

We investigate the nonlinear optical properties of the composite with identical radial-anisotropic/ nonlinear-plasmonic core-shell spherical inclusions randomly embedded in the linear medium. In the weakly-nonlinear case, the enhanced effective third-order nonlinear susceptibility is achieved through the exhibited surface plasmon resonance, and the enhanced peak can be tuned by adjusting the anisotropic parameter. In the strong-nonlinear case, the single optical bistability, double optical bistability or optical tristability in small particles will be found. Furthermore, we demonstrate the optical multistability arising from the high-order modes in low-index surrounding environment for the large particles. And the anisotropy is essential to expand the diversity of the optical switching. Our results are envisioned for the opportunities of anisotropic materials and the applications of the optical switching.

Squeezed-vacuum-induced optical tristability in an atom-cavity system

In this paper we investigate the model of $N$ two-level atoms coupled to a squeezed vacuum inside a coherently driven cavity. By a linear stability analysis in the semiclassical description, we find that the optical tristability emerges in our system owing to the presence of the squeezed vacuum. Moreover, the transition among monostable, bistable, and tristable states can be realized by manipulating the squeezing phase or the squeezing strength of the squeezed vacuum. We also show the signatures of quantum tristability by using the $Q$ function and quantum trajectory methods for the situation of a single atom and low cavity photon number. Our paper offers a way to realize optical tristability in a two-level atomic system.

Realizing optical bistability and tristability in plasmonic coated nanoparticles with radial-anisotropy and Kerr-nonlinearity.

We theoretically study the optical bistability and tristability in plasmonic coated nanospheres containing the nonlinear plasmonic shell and the dielectric core with radial anisotropy. Based on self-consistent mean-field approximation, we establish the relationship between the local field in the shell and the applied incident field, taking into account the Lorentz local field. One or two optical bistabilities and even optical tristability can be observed. Especially, there are two critical geometric parameters between which two optical bistabilities exist. Physically, two optical bistablities result from the excitations of two surface plasmonic resonant modes in the inner and outer interfaces of coated nanospheres, which are well reflected from the spectral representation with two poles. Moreover, the involvement of the radial anisotropy is quite essential to realize the optical tristability. Further discussion on the field-induced tuning of the reflectance reveals the macroscopic properties of this nonlinear optical structure, which provides a potential candidate for designing multi-stable optical devices at the nanoscale.

Frequency-modulated textural formation and optical properties of a binary rod-like/bent-core cholesteric liquid crystal

We explore the mechanisms of voltage-induced textural switching and the corresponding electro-optical responses of a binary cholesteric liquid crystal (CLC) composed of the rod-like nematic LC E7 with positive dielectric anisotropy and the bent-core LC dimer CB7CB with large flexoelectric coefficients. Our results indicate that the minimal voltage (VH) required for retaining the CLC in the homeotropic state and the optical transparency of the CLC after treating with decreasing voltage (from VH to zero) are dependent on the voltage frequency. The observed frequency modulated electro-optical properties are characterized by the frequency regimes separated by the critical frequencies of flexoelectric polarization and dielectric relaxation in dielectric dispersion. These unusual features, specific to the CB7CB-doped CLC, are explained by the dielectric and frequency-dependent flexoelectric responses of LC molecules to an external AC voltage. Accordingly, in addition to the known Grandjean planar and focal conic states, the uniform lying helix as a third stable state can be feasibly generated in the binary CLC with 45 wt% CB7CB by two pathways. The first one is to treat the cell directly with a sufficient voltage lower than VH; the other is to decrease the voltage gradually from VH to zero in the low-frequency regime, where the flexoelectric strength is significant. Manifested by its optical tristability, frequency-controllable optical transparency, and fast flexoelectro-optical response, the proposed binary rod-like/bent-core CLC system is promising for developing a variety of memory- and dynamic-mode photonic and optoelectronic devices.

Controllable optical response properties in a hybrid optomechanical system

In this paper, we study theoretically the optical response properties of the output field in a hybrid optomechanical system, in which a degenerate optical parametric amplifier (OPA) and a $$\varLambda $$ -type three-level atomic ensemble are placed in a driven optical cavity with a moving end mirror. We show that due to the presence of the OPA and the atomic medium, our proposal has the ability to exhibit the optical tristability and multiple optomechanically induced transparency (OMIT)-like effects. Moreover, the combined effects of optical amplification and OMIT-like as well as the tunable switch from slow-to-fast light can be realized by tuning the gain coefficient of the OPA and the phase of the field driving the OPA. In addition, the role of the OPA on the higher-order sideband generation has also been investigated. We find that the presence of the OPA contributes to the enhancement of the second-order sideband generation. These results provide a new way to engineer the hybrid optomechanical devices for applications in optical communications and signal processing.

Tunable Low Threshold Optical Tristability at Terahertz Frequencies via a Pair of Parallel Graphene Layers’ Configuration

We investigate theoretically the optical tristability of transmission at a pair of parallel graphene layers system. We discuss the influence of the graphene sheets on the hysteretic response of the TE-polarized transmitted light. It is demonstrated that the optical tristability in this configuration can be realized due to the giant third-order nonlinear conductivity of graphene and appropriate structure parameters. The tristable behavior of the transmitted light can be controlled via suitably varying the Fermi energy of the graphene. Besides, the optical tristable behavior is strongly dependent on the relaxation time of the graphene and the dispersion characteristics of the surrounding dielectrics. Moreover, the threshold of the optical tristability can be reduced by appropriately increasing the number of graphene layers, making this simple structure a good candidate for dynamic tunable and low threshold optical tristable device in the terahertz (THz) frequencies.

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.

Optical tristability and ultrafast Fano switching in nonlinear magnetoplasmonic nanoparticles

We consider light scattering by a coated magneto-plasmonic nanoparticle (MPNP) with a Kerr-type nonlinear plasmonic shell and a magneto-optic core. Such structure features two plasmon dipole modes, associated with electronic oscillations on the inner and outer surfaces of the shell. Driven in a nonlinear regime, each mode exhibits a bistable response. Bistability of an inner plasmon leads to switching between this state and a Fano resonance (Fano switching). Once the external light intensity exceeds the critical value, the bistability zones of both eigen modes overlap yielding optical tristability characterized by three stable steady states for a given wavelength and light intensity. We develop a dynamic theory of transitions between nonlinear steady states and estimate the characteristic switching time as short as 0.5 ps. We also show that the magneto-optical (MO) effect allows red- and blue- spectral shift of the Fano profile for right- and left- circular polarizations of the external light, rendering Fano switching sensitive to the light polarization. Specifically, one can reach Fano switching for the right circular polarization while cancelling it for the left circular polarization. Our results point to a novel class of ultrafast Fano switchers tunable by magnetic field for applications in nanophotonics.

Optical tristability in a hybrid optomechanical system

In this paper, we investigate a hybrid optomechanical system consisting of two cavities, which one of them is an optomechanical cavity that includes an optical parametric amplifier (OPA) and the other is a traditional cavity which contains an atomic medium. Hamiltonian of the system is written in a rotating frame with a rotation frequency of the frequency of input field to the system. Using Heisenberg-Langevin equations of motion, the dynamics of the system is described. Applying the steady-state conditions leads to a system of equations of the mean values of the operators of the system. The stability condition of the system is satisfied numerically and behavior of optomechanical cavity is investigated in different situations to find the effect of changing of the parameters of the system on the type of its stability. We show proposed system has the capability of tristable behavior, where, the gain coefficient of OPA acts as a switch in changing the bistability of the system to a tristable manner. The building block of the tristability in this system can be figured out as the enhanced nonlinearity of the system due to the presence of OPA.

Optical tristability investigation in two coupled ring resonators

The microring resonators have potential applications for the photonic integrated circuits. The dynamical phenomena of the two coupled microrings require a simple and efficient numerical formalism for solution of the system. We employ an analytical formula to calculate the optical tristability inside the two coupled microrings that takes into account Kerr nonlinearity and the effect of loss. We also compare the analytical results with the results from 3D finite-difference time-domain simulation. In addition, we show it is possible to obtain configurations which can tune the tristable region. This could be useful for designing optical logic applications.

Photonic Bandgap–Cholesteric Device with Electrical Tunability and Optical Tristability in Its Defect Modes

This study proposes a hybrid structure for a one-dimensional (1D) photonic crystal (PC) comprising a tristable cholesteric liquid crystal (CLC) as the defect layer. The CLC exhibits three optically stable states: the Grandjean planar (P), focal conic (FC), and uniform lying helix (ULH) configurations. Specifically, the reflection band of the CLC is set within the photonic bandgap (PBG) of the 1D PC. While the ULH and the FC states can be regarded as the light-on and light-off states for defect-mode peaks in the visible spectrum, respectively, switching the device from the ULH to the P state enables suppression of the transmission of partial defect modes within the PBG. This device possesses many alluring features, such as optical tristability at null applied voltage and transmission tunability of the defect modes, providing a new pathway for the design of multifunctional and energy-efficient optical switches, light shutters, multichannels, and wavelength selectors.

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...

Photo-switchable chiral liquid crystal with optical tristability enabled by a photoresponsive azo-chiral dopant.

A light-driven tristable chiral-tilted homeotropic nematic (TCHN) cell is demonstrated. The liquid-crystal cell is photo-switchable among the three stable states: the tilted-homeotropic, fingerprint, and the tilted-twist states. The inclusion of a photosensitive chiral bis(azobenzene) compound into a typical nematic liquid crystal makes the resulting material possible to switch from one to another stable state directly and reversibly owing to the photoinduced trans-cis isomerization of the azo-chiral dopant and, hence, the configurational change of the liquid crystal via the guest-host effect. By further introducing dichroic dyes into the TCHN system, we devised a polarizer-free display and light modulators. The novel TCHN composite material opens up new possible applications in light-driven optical elements and devices.

Phase space of tristability in dual injection-locked Fabry-Perot laser diodes

By using the model of an optically bistable injection-locked semiconductor Fabry-Perot laser diode, we theoretically investigate the case of dual injection-locking, in which the two light signals are simultaneously externally injected into the cavity of a slave laser. We show that dual injection-locking leads to formation of new stationary points, i.e., to optical tristability of the slave laser. We analyze the range of injection power and frequency detuning for which this tristability occurs.

Multichannel photonic devices based on tristable polymer-stabilized cholesteric textures

We demonstrate in this paper an electrically tunable photonic device based on one-dimensional photonic crystal (PC) infiltrated with polymer-stabilized cholesteric texture (PSCT) as a central defect layer. With the hybrid PC/PSCT structure, not only is the wavelength of each defect mode switchable among three major stable states by various appropriate frequency-modulated voltage pulses, but also the intensity can be electrically tuned in multi-metastable states. As a result, an electrically controllable multichannel photonic device with several alluring features is proposed. It is wavelength-switchable, intensity-tunable, and polarizer-free and possesses optical tristability in the defect modes to reduce power consumption.

Achieving Optical Tri-Stability Through Periodic Metal-Dielectric Structure

Through the modified transfer matrix method, the transmission properties of a one-dimensional coupled-resonator optical waveguide structure composed of metal layers and non-linear material layers is studied. Given proper incident frequency and structure parameters, an optical tri-stability has been achieved. The effect of loss has been considered.

Goos–Hänchen shift of the reflection from nonlinear nanocomposites with electric field tunability

A structure of nonlinear metal-dielectric nanocomposites is proposed to control the lateral shift of the reflected beam by tuning an applied electric field. Based on spectral representation theory and stationary phase method, the lateral shift is found to exhibit hysteretic effects including single optical bistability, double optical bistability, and optical tristability. As a consequence, it can be manipulated via the applied field. Moreover, the shift is strongly dependent on the volume fraction, the shape of the metallic particles, and the incident angle. Numerical simulations based on Gaussian waves are in good agreement with our theoretical calculations.

Wall thickness dependent double optical bistability in gold nanotube: A physical mechanism based on local field enhancement

The intrinsic optical bistability (OB) in a two-phase composite, a nonlinear gold nanotube embedded in a linear dielectric host, is investigated by theoretical calculation. Based on quasistatic approximation and Kerr nonlinearity, we obtain the local electric field in a certain position of the gold nanotube as a function of the incident field. In addition to the single OB, the appearance of double OB and optical tristability are also reported. It is shown that both wavelength and wall thickness can dramatically affect the optical bistable behavior of gold nanotube. Both the critical wavelength and the region of double OB decrease obviously with increasing the wall thickness. Thus double OB only appears in the thinner gold tube and is absent as the wall thickness exceeds the critical value. Furthermore, all these OB characteristics have been explained by the local field enhancement effect.

Optical bistability and tristability in nonlinear metal/dielectric composite media of nonspherical particles.

Based on a spectral representation method and a self-consistent mean field theory, we present a general framework to investigate the optical bistability in a nonlinear two-phase composite, where spheroidal metallic inclusions are randomly oriented and embedded in a dielectric host. The relation between the spatial average of the local field squared <[absolute value of E](2)>(i) (i=1,2) and the external field squared E20 is obtainable through the spectral density function which is predicted from our recently derived Maxwell-Garnett approximation. In addition to single optical bistability (OB), the appearance of double OB and optical tristability (OT) is reported, and the corresponding phase diagram is given. We find that the regions of the single OB, the double OB, and the OT are dependent on the shape and volume fraction of the metallic particles. Our method allows us to take one step forward to study some field-dependent effective optical properties, such as the refractive index, extinction coefficient as well as reflectance. The general framework is also applied to investigate exactly the solvable composites consisting of nonlinear spheroidal inclusions and linear dielectric host in the dilute limit. To this end, the present method is shown to be in excellent agreement with the exact solution. In addition, the present method predicts a larger threshold intensity than the variational approach.

Bilateral Symmetry Breaking in a Nonlinear Fabry-Pérot Cavity Exhibiting Optical Tristability

We show the existence of a region in the parameter space that defines the field dynamics in a Fabry-Perot cylindrical cavity, where three output stable stationary states of the light are possible for a given localized incident field. Two of these states do not preserve the bilateral (i.e. left-right) symmetry of the entire system. These broken-symmetry states are the high-transmission nonlinear modes of the system. We also discuss how to excite these states.