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Bistability in the current–voltage characteristics of semiconductor superlattices and quantum cascade laser structures has the potential for wide-ranging applications, particularly in sensing systems. However, the interdependency of applied bias and current injection in conventional two-terminal structures has led to complications in analysis and rendered the bistability phenomenon difficult to implement in practical applications. Here, we report a new kind of electronic bistability coupled to optical switching in a resonant tunneling bipolar superlattice transistor. This bistability manifests as sharp discontinuities in the collector current with extremely small variations of the applied voltage, which arise from unstable tunneling transmission across the hetero-barrier between the two-dimensional electron gas (2DEG) at the edge of the transistor base and the collector superlattice structure. The electronic transitions between high and low quantum mechanical transmissions are demonstrated to be caused by self-consistent variations of the internal electric field at the heterointerface between the 2DEG and the superlattice. They are also present in the base current of the three-terminal device and result in sharp switching of near-infrared spontaneous light emission output from an interband radiative recombination process with a peak emission wavelength of 1.58 μ m. A comprehensive quantum mechanical theoretical model accounting for the self-consistent bistable tunneling transmission is in quantitative agreement with the experimental data. The measured peak transconductance sensitivity value of 6000 mS can be used in the highly sensitive detector and non-linear device applications. [ABSTRACT FROM AUTHOR]

We theoretically study the optical bistability assisted by multipole polarizations in a semiconductor quantum dot (SQD)/metal nanoparticle (MNP) hybrid molecule. We map out bistability phase diagrams within the parameter subspace spanned by (the pumping intensity Ipu, interparticle distance, d) under dipole and multipole approximations. It is shown that the Ipu-correlated bistable region will be broadened greatly in the strong exciton–plasmon coupling regime, and the corresponding lower (upper) bistable threshold is enlarged significantly due to multipole polarization (N = 10) in comparison to that in the dipole approximation (N = 1). However, under the same conditions, the d-correlated bistable region is shrunk at high pump intensities. Our contribution not only offers a better understanding of exciton–plasmon coupling systems but also expands the application of SQD/MNP hybrid molecules in the field of optical bistable nanodevices. [ABSTRACT FROM AUTHOR]

Self-organization of radiation in random media is a key to controlling the optical energy flow and constitutes the basis of innovative cavity-free laser designs. Here, we theoretically demonstrate the existence of robust temporal dissipative soliton molecules in a graphene-based active disordered metamaterial. We observe that localized pulses with single and multiple peaks can coexist inside this metamaterial for a wide range of gain parameters, thereby exhibiting optical bistability. We further investigate the stability of such bound states under perturbation by analyzing their interaction force, finding stable tri-soliton molecule states with a periodically oscillating relative phase and a stable bi-soliton molecule. Our results offer a paradigm for mode-locking in active random metamaterials and pave the way for versatile applications such as multilevel encoding in optical communications, future designs of low-cost cavity-free lasers, and optical amplifiers. [ABSTRACT FROM AUTHOR]

The widespread adaptation of systems relying on optically controlled quantum information will require reliable and efficient multi-channel fiber-to-chip connections that function at cryogenic temperatures. Here we demonstrate low loss (2 dB per channel) connections between a single mode fiber array and tapered silicon waveguides down to 5 K using polymer based photonic wire bonds (PWBs). A method is described for assembling the silicon chip and fiber array such that the PWB connections are robust to temperature cycling and cryostat bakeout. The threshold power handling capability of the PWBs is greater than 4 dBm, sufficient to demonstrate optical bistability in silicon microring resonators coupled to the waveguides at 5 K. [ABSTRACT FROM AUTHOR]

Utilizing the modified transfer matrix method, under transverse electric polarization, asymmetric optical bistability is achieved by designing one-dimensional photonic crystals (PCs) with two Bragg reflector segments containing traditional dielectrics and asymmetric defect multilayers consisting of a magnetized ferrite and nonlinear Kerr dielectric. When the incident wave frequency equals the resonance frequency, owing to the breaking of symmetry in the defect layers and the Voigt magneto-optical effect generating in the magnetized ferrite layers together with the Kerr effect existing in the Kerr dielectric layers, the asymmetric optical modulations are presented as the bistable state in the forward propagation and the multistable state in the backward propagation. Also, the diverse energy localization distributions of the electric field in the proposed PCs from the two incident directions are graphically illustrated. Furthermore, the optical bistable switch-up and switch-down thresholds of the proposed resonator can be tailored flexibly by the external magnetic field, the incident angle, the thicknesses of different dielectrics, and the nonlinear coefficient of Kerr dielectric. This work provides a constructive proposal for the design of light modulators, such as the optical isolator, the optical triode, the all-optical diode, and the sensor. [ABSTRACT FROM AUTHOR]

Exciton–polaritons in optical cavities exhibit strong nonlinearities predominantly because of the third-order Kerr-like interactions mediated by the excitonic component. Under quasi-resonant excitation, depending on the energy of the incident laser, it results in the optical limiting or bistable behavior. The latter phenomenon is manifested by the hysteresis loop observed in the input–output power characteristics, when a cavity is quasi-resonantly driven by a laser field. The direction of the loop is typically counterclockwise when increasing and subsequently decreasing the optical power. In this work, we demonstrate the optical bistability with an inverted hysteresis direction. It is observed in an exfoliated CdTe-based semiconductor microcavity when the frequency of the pumping laser is tuned slightly below the lower polariton mode. This unusual behavior is caused by the interplay of the suppression of strong coupling and the redshift of the lower polariton mode energy when increasing the incident power. We show that under these conditions, the polariton microcavity can be used as an optical limiter. All of the experimental observations, the shape and the direction of the hysteresis and the optical limiting behavior, are fully supported by a theoretical model. [ABSTRACT FROM AUTHOR]

We investigate the third-order optical nonlinearity in silicon nitride (SiN) films prepared using magnetron sputtering. The large nonlinear refractive index n2 in SiN prepared at room temperature of a value of −2.00 × 10−16 m2/W and the nonlinear absorption coefficient β of 1.44 × 10−9 m/W are determined by the Z-scan method at a wavelength of 1064 nm and a pulse duration of 25 ps. The n2 is three orders of magnitude larger than that in SiN films prepared by the chemical vapor deposition method and at a wavelength of 1.55 μm. The enhanced n2 up to −6.27 × 10−16 m2/W and the slightly changed β, indicating an enhanced ratio of |Reχ(3)|/|Imχ(3)|, are further obtained in the annealed samples. Such a change is probably due to the crystallization of the films. The optical bistability in SiN resonant waveguide grating (RWG) is numerically studied. The low threshold intensity around 300 MW/cm2 in the RWG is obtained. [ABSTRACT FROM AUTHOR]

We study the optical response of a coupled asymmetric semiconductor quantum dot-spherical metal nanoparticle structure. The asymmetric quantum dot has permanent electric dipole moments that also interact with light. We derive the density matrix equations for the system including the modification of the electric field and the exciton-plasmon coupling. We emphasize on the effects of the nonlinear optical rectification and controlled optical bistability and analyze these phenomena for different values of the light intensity and different distances between the quantum dot and the metal nanoparticle. We show that when the system is set in a situation where optical bistability can be produced, the optical rectification of the hybrid system is bivalued. We also analyze the slow-down to reach the steady state when the system is driven close and far from the turning points. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Practical graphene-comprising resonant structures are proposed for high-quality Kerr-induced bistability with a low input power. Two structures are designed for operation in the far-infrared (FIR) and near-infrared (NIR) frequency regimes, respectively. The nonlinear response is studied by utilizing a theoretical framework combining perturbation theory and coupled-mode theory, capable of accurately and efficiently modeling resonant structures with dispersive bulk and sheet materials. The FIR system is based on a side-coupled graphene-nanoribbon ring resonator, formed by applying a bias voltage between a uniform graphene sheet and an uneven silicon substrate. By optimizing the system geometry, we demonstrate bistable response with a theoretically infinite extinction ratio between states and an operating power of only 400 μW at 10 THz. In the NIR circuit, a silicon photonic ring resonator is overlaid with a graphene sheet. The silicon-slot geometry is judiciously chosen to maximize the field overlap with graphene, resulting in low power requirements of 90 mW at 1:55 μm. In both cases, nonlinearity stems from the instantaneous Kerr effect in graphene, allowing for ultra-fast response. Combining low input power and fast response times, the proposed components highlight the potential of graphene for nonlinear applications over a broad spectral range. [ABSTRACT FROM AUTHOR]

We demonstrate a low power thermally induced optical bistability at telecom wavelengths and room temperature using a nanobeam photonic crystal cavity embedded with an ensemble of quantum dots. The nanobeam photonic crystal cavity is transfer-printed onto the edge of a carrier chip for thermal isolation of the cavity with an efficient optical coupling between the nanobeam waveguide and optical setup. Reflectivity measurements performed with a tunable laser reveal the thermo-optic nature of the nonlinearity. A bistability power threshold as low as 23 μW and an on/off response contrast of 6.02 dB are achieved from a cavity with a moderately low quality factor of 2830. Our device provides optical bistability at power levels an order of magnitude lower than previous quantum-dot-based devices. [ABSTRACT FROM AUTHOR]

We revisit the laser model with cavity loss modulation, from which evidence of chaos and generalized multistability was discovered in 1982. Multistability refers to the coexistence of two or more attractors in nonlinear dynamical systems. Despite its relative simplicity, the adopted model shows us how the multistability depends on the dissipation of the system. The model is then tested under the action of a secondary sinusoidal perturbation, which can remove bistability when a suitable relative phase is chosen. The surviving attractor is the one with less dissipation. This control strategy is particularly useful when one of the competing attractors is a chaotic attractor. [ABSTRACT FROM AUTHOR]

In this paper, we present the experimental observation of simultaneous bi-directional superluminal lasing in a triangular ring cavity without gain competition and crosstalk as needed for realizing a gyroscope based on the Sagnac effect. The gain spectrum for each of the lasers is tailored to be a narrow dip on top of a broad gain using two stable isotopes of Rb. Specifically, we make use of 85Rb to produce a broad gain spectrum via the optically pumped Raman gain process and 87Rb to produce a narrow absorption spectrum via the optically pump Raman depletion process. A separate gain cell is used for the laser in each direction. Inferred from the simulation, the spectral sensitivity enhancements of the clock-wise and counter-clock-wise superluminal ring lasers are ∼362 and ∼505, respectively, with the imbalance attributed to differences in pump powers. [ABSTRACT FROM AUTHOR]

Here, we study the electromagnetic response of asymmetric mushroom-type metamaterials loaded with nonlinear elements. It is shown that near a Fano resonance, these structures may have a strong tunable, bistable, and switchable response and enable giant nonlinear effects. By using an effective medium theory and full wave simulations, it is proven that the nonlinear elements may allow the reflection and transmission coefficients to follow hysteresis loops, and to switch the metamaterial between "go" and "no-go" states similar to an ideal electromagnetic switch. [ABSTRACT FROM AUTHOR]

We propose to realize an optical isolator based on backward Brillouin scattering in a whispering-gallery-mode (WGM) cavity that supports both traveling optical and acoustic waves. When the WGM cavity is optically driven in one direction, the time-reversal symmetry for light transmission is broken due to the unidirectional photon–phonon coupling. We show that the signal light is either transmitted or completely absorbed depending on whether it propagates in the same or opposite direction as the strong pump laser. The perfect absorption can be interpreted as a phase transition in a parity–time–symmetric Hamiltonian with the balanced gain and loss. The present work paves a way for the realization of an on-chip optical isolator with the high degree of isolation, large bandwidth, and low insertion loss simultaneously. [ABSTRACT FROM AUTHOR]

Theoretical investigation of optical switching in a plasmonic device comprising a metaldielectric-metal waveguide perpendicularly coupled to a single nanocavity is reported. The cavity is filled with a third order nonlinear Kerr material whose optical properties are manipulated using a control beam to trigger the switching operation. The performance of the switch is quantitatively evaluated and compared with other switching mechanisms used in a similar plasmonic structure. The comparative study reveals that the efficiency of our plasmonic switch is many folds higher and hence advantageous over absorption switching. The dependence of switching efficiency on material parameters and input intensity of the control illumination is demonstrated in detail. Switching efficiency is calculated using various nonlinear crystals, glasses, liquids, and other materials. Bistability study and consequent determination of the hysteresis loop width provides an idea of required threshold intensity and sensitiveness of the nonlinear plasmonic switch. [ABSTRACT FROM AUTHOR]

The paper presents a theoretical study of the modulation instability of a continuous or quasicontinuous optical probe in a three level quantum well system under electromagnetically induced transparency. The modulation instability is affected by the control field detuning, as well as even-order dispersion and by the strength of Kerr (third-order) and quintic (fifth-order) nonlinearities. The fourth-order dispersion reduces the bandwidth over which modulation instability occurs, whereas the quintic nonlinearity saturates the growth of the modulation instability. Detuning the control field from resonance can significantly reduce the growth of the modulation instability at both low and high power levels. At low powers, the system becomes stable against modulation instability for small detuning of the control field and at high powers modulation instability disappears for larger detuning. [ABSTRACT FROM AUTHOR]

Studies of implant activation in InAs have not been reported presumably because of challenges associated with junction leakage. The activation of 20 keV, Si+ implants into lightly doped (001) p-type bulk InAs performed at 100 °C as a function of annealing time and temperature was measured via Raman scattering. Peak shift of the L+ coupled phonon-plasmon mode after annealing at 700 °C shows that active n-type doping levels ≈5×1019cm–3 are possible for ion implanted Si in InAs. These values are comparable to the highest reported active carrier concentrations of 8–12×1019cm–3 for growth-doped n-InAs. Raman scattering is shown to be a viable, non-contact technique to measure active carrier concentration in instances where contact–based methods such as Hall effect produce erroneous measurements or junction leakage prevents the measurement of shallow n+ layers, which cannot be effectively isolated from the bulk. [ABSTRACT FROM AUTHOR]

A one-dimensional photonic crystal structure with a nonlinear metal-dielectric nanocomposite defect layer is proposed to control the optical bistability (OB) of the transmitted wave by tuning the externally applied dc electric field. Using the transfer matrix method for dielectric layers and solving the Helmholtz nonlinear equation in the nonlinear composite layer, the linear transmittance spectrum and the nonlinear transmission curve are illustrated graphically for different applied fields. A field-dependent defect mode is observed in the linear transmittance spectrum. Consequently, the OB switch-up and -down thresholds can be manipulated via the applied field intensity. Due to the field dependence of composite layer refractive index, the physical response of the observation is the dynamical shifting of the defect mode. Moreover, it is shown that the volume fraction, shape, and type of the embedded nanoparticles as well as the kind of the dielectric host have large influences on the OB threshold. The proposed structure has significant potential applications in optical integrated devices. [ABSTRACT FROM AUTHOR]

The optical bistability and multistability properties of a four-level quantum system near a plasmonic nanostructure embedded in a unidirectional ring cavity are studied theoretically. Two orthogonal circularly polarized laser fields with the same frequency, different phases and electric fields amplitude are interacted by four-level quantum system. It is found that in the presence of the plasmonic nanostructure, the bistable behaviors related to one of the laser fields propagating through the unidirectional ring cavity can be modified by relative phase and amplitude control of another laser fields. Our obtained results show that the optical bistability can be converted into the optical multistability by varying the value of distance between the quantum system and the surface of the plasmonic nanostructure. Moreover, it is shown that under specific condition related to the distance, the lasing without population inversion can be obtained. [ABSTRACT FROM AUTHOR]

Yttrium iron garnet (YIG) is a magnetic insulator with record-low damping, allowing spin-wave transport over macroscopic distances. Doping YIG with gallium ions greatly reduces the demagnetizing field and introduces a perpendicular magnetic anisotropy, which leads to an isotropic spin-wave dispersion that facilitates spin-wave optics and spin-wave steering. Here, we characterize the dispersion of a gallium-doped YIG (Ga:YIG) thin film using electrical spectroscopy. We determine the magnetic anisotropy parameters and Gilbert damping from the frequency and linewidth of the ferromagnetic resonance (FMR). Next, we use propagating spin wave spectroscopy in the Damon–Eshbach configuration to detect the small spin-wave magnetic fields of this ultrathin weak magnet over a wide range of wavevectors, enabling the extraction of the exchange constant α ex = 1.3 2 × 10 − 12 J / m. We observe foldover of the FMR with increasing drive power, leading to frequency shifts of the spin-wave modes and a bistable region in the spin-wave spectra. Our results shed light on isotropic spin-wave transport in Ga:YIG and highlight the potential of electrical spectroscopy to map out the dispersion and bistability of propagating spin waves in magnets with a low saturation magnetization. [ABSTRACT FROM AUTHOR]

Phase solitons are localized structures characterized by phase jumps of 2 π or multiples arising in forced ring lasers. Here, we show numerically that they can be created by superimposing to the constant driving field a suitable control beam matched in frequency with a different cavity mode for a time of the order of ten cavity round trip times. If the two beams are separated in frequency by n free spectral ranges of the cavity, a train of solitons like a perfect soliton crystal consisting of n equispaced phase solitons is generated. This may represent a simple way to produce frequency combs with flexible frequency spacing and high power per line. [ABSTRACT FROM AUTHOR]

The effects of confinement on colloidal self-assembly in the case of fixed number of confined particles are studied in the one dimensional lattice model solved exactly in the grand canonical ensemble (GCE) in Pkalski et al. [J. Chem. Phys. 142, 014903 (2015)]. The model considers a pair interaction defined by a short-range attraction plus a longer-range repulsion. We consider thermodynamic states corresponding to self-assembly into clusters. Both fixed and adaptive boundaries are studied. For fixed boundaries, there are particular states in which, for equal average densities, the number of clusters in the GCE is larger than in the canonical ensemble. The dependence of pressure on density has a different form when the system size changes with fixed number of particles and when the number of particles changes with fixed size of the system. In the former case, the pressure has a nonmonotonic dependence on the system size. The anomalous increase of pressure for expanding system is accompanied by formation of a larger number of smaller clusters. In the case of elastic confining surfaces, we observe a bistability, i.e., two significantly different system sizes occur with almost the same probability. The mechanism of the bistability in the closed system is different to that of the case of permeable walls, where the two equilibrium system sizes correspond to a different number of particles. [ABSTRACT FROM AUTHOR]

In this study, we investigate the optical bistability and multistability in a pure single Kerr nonlinear layer of dielectric material using the Maxwell-Duffing approach. We employ the Duffing anharmonic oscillator as an alternative constitutive relation to express the electric field as a nonlinear function of the induced polarization. Utilizing both the electromagnetic wave equation and the Duffing constitutive relation, we obtain a nonlinear polarization equation propagates through the nonlinear layer under the slowly varying envelope approximation. With the application of boundary conditions at both interfaces, expressions for the incident, reflected, and transmitted intensities of the light wave are obtained as nonlinear functions of the polarization and other controlling parameters. For realistic input parameters, our numerical results demonstrated the existence of an intrinsic optical bistability (IOB) in a pure single dielectric layer. Furthermore, the threshold value of the observed IOB depends essentially on the value Eth, i.e., the minimum value required to invoke the third-order nonlinearity inside the material. For operating frequency near the sharp resonance region, Eth was found to be ≈105V/cm; this is equivalent to a threshold value of the optical intensity ≈1010W/cm2. With the developments in THz sources, it is nowadays possible to observe this IOB experimentally by tuning the operating frequency near the sharp resonance region of the material. Steps to get the threshold value of Eth are also advised. [ABSTRACT FROM AUTHOR]

The solution of input-output curves in an optical ring cavity containing Landau-quantized graphene is theoretically investigated taking the advantage of density-matrix method. It is found that under the action of strong magnetic and infrared laser fields, one can efficiently reduce the threshold of the onset of optical bistability (OB) at resonance condition. At non-resonance condition, we observed that graphene metamaterial can support the possibility to obtain optical multistability (OM), which is more practical in all-optical switching or coding elements. We present an analytical approach to elucidate our simulations. Due to very high infrared optical nonlinearity of graphene stemming from very unique and unusual properties of quantized Landau levels near the Dirac point, such controllability on OB and OM may provide new technological possibilities in solid state quantum information science. [ABSTRACT FROM AUTHOR]

The spontaneously generated coherence (SGC) effects on optical bistability (OB) are investigated in a five-level K-type system. It is found that SGC makes the system phase dependent. Thus, the OB and the absorption behavior of the system can be controlled by the relation phase of applied fields. In addition, the pump field intensity effect on the OB behavior is discussed. The experimental viability of the model in semiconductor quantum well system is also discussed [A. V. Germanenko et al., J. Phys.: Conf. Ser. 376, 012024 (2012); D. S. Chemla et al., IEEE J. Quantum Electron. 20(3), 265 (1984); L. V. Butov et al., J. Exp. Theor. Phys. 88(5), 1036 (1999); J. F. Dynes et al., Phys. Rev. Lett. 94, 157403 (2005); S. Schmitt-Rinka et al., Adv. Phys. 38(2), 89 (1989); and H. W. Liu et al., Appl. Phys. Lett. 54, 2082 (1989)]. [ABSTRACT FROM AUTHOR]

The interaction between two particles made of an isotropic linearly polarizable magnetic material and embedded in an elastomer matrix is studied. In this case, when an external field is imposed, the magnetic attraction of the particles, contrary to point dipoles, is almost wraparound. The exact solution of the magnetic problem in the linear polarization case, although existing, is not practical; to circumvent its use, an interpolation formula is proposed. One more interpolation expression is developed for the resistance of the elastic matrix to the field-induced particle displacements. Minimization of the total energy of the pair reveals its configurational bistability in a certain field range. One of the possible equilibrium states corresponds to the particles dwelling at a distance, the other-to their collapse in a tight dimer. This mesoscopic bistability causes magnetomechanical hysteresis which has important implications for the macroscopic behavior of magnetorheological elastomers. [ABSTRACT FROM AUTHOR]

By applying an asymmetric on-site restoring force in a 1D chain of oscillators, we demonstrate experimentally that a morphing in the bandgap structure or passive bandgap reconfiguration can be triggered by an increase in environmental excitation amplitude. Recent studies on wave propagation have focused on new capabilities and behaviors resulting from intrinsic nonlinearities. This paper details a bistable experimental design that achieves amplitude dependent filtering through passive bandgap reconfiguration, which is triggered by a bifurcation. The system studied comprises a 1D chain of axially aligned pendulums in dimer unit cells with geometrically nonlinear nearest neighbor coupling where bistability is induced through repulsive magnets. When the bistability is asymmetric, each potential well has a different linear spectra. Though this paper uses mechanically coupled oscillators as an example, the phenomenon itself could be used in any wave propagation media where asymmetric bistability can be implemented. [ABSTRACT FROM AUTHOR]

The behaviour of materials under spatial confinement is sensitively dependent on the nature of the confining boundaries. In two dimensions, confinement within a hard circular boundary inhibits the hexagonal ordering observed in bulk systems at high density. Using colloidal experiments and Monte Carlo simulations, we investigate two model systems of quasi hard discs under circularly symmetric confinement. The first system employs an adaptive circular boundary, defined experimentally using holographic optical tweezers. We show that deformation of this boundary allows, and indeed is required for, hexagonal ordering in the confined system. The second system employs a circularly symmetric optical potential to confine particles without a physical boundary. We show that, in the absence of a curved wall, near perfect hexagonal ordering is possible. We propose that the degree to which hexagonal ordering is suppressed by a curved boundary is determined by the "strictness" of that wall. [ABSTRACT FROM AUTHOR]

We investigate optical bistability (OB) behavior in an asymmetric three-coupled quantum well structure inside a unidirectional ring cavity. By controlling the assisting coherent driven field and the frequency detunings of the two control laser fields, we find that the appearance and disappearance of OB can easily be controlled by adjusting the positions of the dual electromagnetically induced transparency windows. Analysis in the dressed-state picture is also given. Our scheme may be used for building more efficient all-optical switches and logic-gate devices for optical computing and quantum information processing. [ABSTRACT FROM AUTHOR]

Mitogen-activated protein kinases (MAPKs) are important signal transducing enzymes, unique to eukaryotes, that are involved in many pathways of cellular regulation. Successive phosphorylation cascades mediated by MAPKs serve as sensitive switches initiating various cellular processes. Apart from this basic feature, the underlying reaction network is capable of displaying other nonlinear phenomena including bistable steady states and hysteresis as well as periodic oscillations. We show that from the mechanistic point of view, bistability is a consequence of interaction between single and double phosphorylation/dephosphorylation pathways in a Stage 2 subsystem of the Huang-Ferrell model. Within this subsystem we uncover the core subnetwork obtained by systematic reduction relying on the methods of stoichiometric network analysis. For the core model we show that there is either one stable steady state or three steady states of which two are stable and point out the role of interplay between the single and double phosphorylation subnetworks in generating bistability. [ABSTRACT FROM AUTHOR]

We present a novel locking scheme for active length-stabilization and frequency detuning of a cavity optomechanical device based on the optical spring effect. The error signal is generated by utilizing the position measurement of a thermally driven intra-cavity nanomechanical device and employing its detuning-dependent frequency shift caused by the dispersive coupling to the cavity field. The scheme neither requires external modulation of the laser or the cavity nor does it demand for additional error signal readout, rendering its technical implementation rather simple for a large variety of existing optomechanical devices. Specifically, for large-linewidth microcavities or in situations where other locking schemes appear unfavorable conceptually or are hard to realize technically, the optical spring lock represents a potential alternative for stabilizing the cavity length. We explain the functional principle of the lock and characterize its performance in terms of bandwidth and gain profile. [ABSTRACT FROM AUTHOR]

A ring resonator made of a silica-based optical fiber is a paradigmatic system for the generation of dissipative localized structures or dissipative solitons. We analyze the effect of the non-instantaneous nonlinear response of the fused silica or the Raman response on the formation of localized structures. After reducing the generalized Lugiato–Lefever to a simple and generic bistable model with a nonlocal Raman effect, we investigate analytically the formation of moving temporal localized structures. This reduction is valid close to the nascent bistability regime, where the system undergoes a second-order critical point marking the onset of a hysteresis loop. The interaction between fronts allows for the stabilization of temporal localized structures. Without the Raman effect, moving temporal localized structures do not exist, as shown in M. G. Clerc, S. Coulibaly, and M. Tlidi, Phys. Rev. Res. 2, 013024 (2020). The detailed derivation of the speed and the width associated with these structures is presented. We characterize numerically in detail the bifurcation structure and stability associated with the moving temporal localized states. The numerical results of the governing equations are in close agreement with analytical predictions. [ABSTRACT FROM AUTHOR]

We demonstrate high efficiency wavelength conversion via four wave mixing in amorphous silicon carbide ring resonators with a loaded quality factor of 70 000. Owing to the high quality factor and high nonlinearity of amorphous silicon carbide, −21 dB conversion efficiency is achieved with 15 mW pump power. Moreover, the thermo-optic coefficient (TOC) of amorphous silicon carbide is measured to be 1.4 × 10−4/°C at telecommunication wavelengths. Taking advantage of the high TOC, we demonstrate optical bistability in the silicon carbide ring resonator. This work presents amorphous silicon carbide as a promising platform for applications in optical signal processing. [ABSTRACT FROM AUTHOR]

We report on the observation of significant optical bistability in the transmission and reflection properties of mesoporous silicon microcavities when illuminated with a 150 ns pulsed laser at 532 nm. The observed optical hysteresis is shown to be transient in nature and the properties are strongly dependent on the porosity of the cavity layer. The onset and damage threshold intensity are also shown to be porosity dependent. Our modeling suggests that the observed effects are due to changes in the nonlinear refractive index where the transient lifetime increases with increasing porosity. We investigate the role of surface states on influencing the bistable process by passivating the internal porous surface with hydrosilylation chemistry. [ABSTRACT FROM AUTHOR]

We study theoretically the conditions under which optical bistability is achievable in a two-subband system in a semiconductor quantum well. We consider the interaction of the two-subband system with a continuous wave electromagnetic field, which induces intersubband transitions. For the description of the system dynamics we use the effective nonlinear density matrix equations. We solve these equations analytically, in the steady state, for a GaAs/AlGaAs quantum well structure. For several combinations of the values of the parameters three real solutions of the population inversion arise and the phenomenon of optical bistability prevails. [ABSTRACT FROM AUTHOR]

The effect of the electrostatic Coulomb interaction on the line shape related to the intensity-dependent intersubband optical processes in a Si δ-doped quantum well is studied using the density matrix formalism. The electronic structure of the quantum well is calculated from the self-consistent numerical solution of the coupled Schrödinger-Poisson equations. The line shape function is considerably modified by the optical intensity and the electric and magnetic fields. Moreover, we demonstrate the existence of the optical bistability for appropriate values of the optical intensity and also the control of the optical bistability with the electric and magnetic fields. It is also found that the intersubband relaxation time plays an important role in determining the optical bistability region. [ABSTRACT FROM AUTHOR]

Upconversion lasing and fluorescence from active microspheres fabricated from a novel fluorozirconate, Er3+ doped glass, ZBNA (ZrF4–BaF2–NaF–AlF3), when pumped at 978 nm via a tapered optical fiber is demonstrated. An ultralow, green lasing threshold of ∼3 μW for 550 nm emissions is measured. This is one order of magnitude lower than that previously reported for ZBLAN (ZrF4–BaF2–LaF3–AlF3–NaF) microspheres. Optical bistability effects in ZBNA microspheres are reported and the bistable mechanism is discussed and attributed to shifts of the whispering gallery modes due to thermal expansion of the sphere, where heating is achieved by optical pumping around 978 nm. The effect of the bistability on the upconversion lasing is examined and we report multiple bistability loops within the microspheres. [ABSTRACT FROM AUTHOR]

Coupled-cluster response theory for frequency-dependent optical properties within the coupled-cluster singles-and-doubles model (CCSD) has been derived and implemented for ansatz 2 of the explicitly correlated CCSD(R12) and CCSD(F12) methods as part of the program package DALTON. The basis set convergence of static dipole moments, polarizabilities, and parallel averages of first and second hyperpolarizabilities has been investigated for Ne, BH, N2, CO, and BF. The frequency-dependent results are presented for the electronic second-harmonic generation of N2. With triple-ζ basis sets, the CCSD(F12) correlation contributions using ansatz 2 are close to the basis set limits for dipole moments and second hyperpolarizabilities; the CCSD(R12) results are better than the CCSD results obtained with at least quintuple-ζ basis sets for polarizabilities and first hyperpolarizabilities. The exponent of Slater-type correlation factor for CCSD(F12) ground state energy may not be optimal and has to be re-examined for response properties. We also suggest that the remaining one-electron basis set errors arising within the coupled-cluster singles should be reduced by allowing excitations into the auxiliary orbital space. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We propose a dual mode liquid crystal display (LCD), which can realize dynamic and memory operating LCD modes in a display panel. Horizontal switching and bistable chiral splay nematic LCD modes are used for the dynamic and memory operations, respectively. As the horizontal switching is applied to the dynamic operation, it is possible to use the same LC texture of splay for realizing dark states of both the dynamic and memory operations. Because, for each operation, pixel division is not required in the proposed dual mode LCD, there is no decrease in aperture ratio and resolution. In order to obtain superior display performance for both operations, a wideband half-wave configuration is employed to the proposed dual mode LCD. Due to the wideband configuration, very low light leakages at the dark state and good dispersion characteristics for the entire visible range are obtained. As a result, the proposed dual mode LCD shows a high contrast ratio of over 100:1 for both the dynamic and memory operations. [ABSTRACT FROM AUTHOR]

We generalize our recent work on the optical bistability of thin films of molecular aggregates [J. A. Klugkist et al., J. Chem. Phys. 127, 164705 (2007)] by accounting for the optical transitions from the one-exciton manifold to the two-exciton manifold as well as the exciton-exciton annihilation of the two-exciton states via a high-lying molecular vibronic term. We also include the relaxation from the vibronic level back to both the one-exciton manifold and the ground state. By selecting the dominant optical transitions between the ground state, the one-exciton manifold, and the two-exciton manifold, we reduce the problem to four levels, enabling us to describe the nonlinear optical response of the film. The one- and two-exciton states are obtained by diagonalizing a Frenkel Hamiltonian with an uncorrelated on-site (diagonal) disorder. The optical dynamics is described by means of the density matrix equations coupled to the electromagnetic field in the film. We show that the one- to two-exciton transitions followed by a fast exciton-exciton annihilation promote the occurrence of bistability and reduce the switching intensity. We provide estimates of pertinent parameters for actual materials and conclude that the effect can be realized. [ABSTRACT FROM AUTHOR]

Wedge bistable chiral tilted-homeotropic nematic liquid crystal (BHN LC) cells with various pretilt angles are experimentally manufactured. The bistable ranges were determined experimentally and by simulation. The crucial influence of BHN LC cells on the d/p (thickness to pitch ratio of LC cell) range in the BHN cell is determined in detail by dynamic simulation. The onset of bistability is determined by the relaxing elastic restoring force, and the relevant physical mechanism is elucidated as well. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate optical bistability in Er3+-Yb3+ phosphate glass microspheres at 295 K. Bistability is associated with both Er3+ fluorescence and lasing behavior, and chromatic switching. The chromatic switching results from an intrinsic mechanism exploiting the thermal coupling of closely spaced energy levels, and occurs simultaneously with the intensity switching. A contrast ratio of 2.8 has been obtained for chromatic switching. The intensity switching shows ratios of 21 for 520 nm and 11 for 660 nm fluorescence emissions, and 11 for IR lasing at 1.5 μm. Concurrent with these observations, we investigate a temperature-dependent absorption of pump power, which exhibits bistable behavior. The influences of the host matrix on lasing and fluorescence mechanisms are highlighted. [ABSTRACT FROM AUTHOR]

The kinetics of CO oxidation on Pt-group metals are known to often exhibit bistability. During the low-reactive regime observed at relatively high CO pressure, the surface is primarily covered by CO and the reaction rate is controlled by O2 dissociation. During the high-reactive regime at relatively low CO pressure, in contrast, the surface is mainly covered by oxygen and the reaction rate is proportional to CO pressure. In the latter case, the adsorbed oxygen may be in the chemisorbed state and/or may form surface oxide. The experiments indicate that the formation of surface oxide often occurs via the island growth and accordingly should be described in terms of the theory of first-order phase transitions. Here, the author proposes a generic lattice-gas model satisfying this requirement and allowing one to execute the corresponding Monte Carlo simulations. Systematically varying the model parameters determining the oxide stability, he classifies the likely scenarios of the bistable reaction kinetics complicated by oxide formation. [ABSTRACT FROM AUTHOR]

A linear one-dimensional dissipative model is proposed and applied in obtaining numerical simulation results for coupled double quantum dot cells, for single-electron transport dynamics on each cell. Field coupling between cells is modeled simply from a matrix of mutual capacitances. Bistability with only one excess electron on each cell, in a pair of coupled double-dot cells, is demonstrated. Behavior prediction and performance evaluation, for applications such as computational system implementation, are made possible. It is understood from the simulations that balanced dissipation rates are essential for the implementation of optimized single-electron devices, with short settling times. [ABSTRACT FROM AUTHOR]

We study theoretically the vertical electron transport in semiconductor multiple-quantum-well structures, where sequential tunneling between neighboring wells takes place. The nonuniformity of electric field along the growth axis and charge redistribution among the quantum wells, as well as between the inner wells and contacts, are taken into account. A simple and efficient model of charged contact layers is proposed. The calculated I-V curves exhibit regions of conventional N-shaped negative differential conductivity and Z-shaped portions of intrinsic bistability, both arising due to the tunneling resonances. A general explanation of their formation mechanism is given, which is valid for any form of interwell transitions of resonant nature. The conditions of N- and Z-shaped curve observation and controllable transition between them are discussed. [ABSTRACT FROM AUTHOR]