Optical Bistable Devices Research Articles

Controlling Fano resonances in multilayer dielectric gratings towards optical bistable devices

The spectral properties of Fano resonance generated in multilayer dielectric gratings (MDGs) are reported and numerically investigated in this paper. We examine the MDG consisting of numerous identically alternative chalcogenide glass (As2S3) and silica (SiO2) multilayers with several grating widths inscribed through the structure, emphasizing quality (Q) and asymmetric (q) factors. Manipulation of Fano lineshape and its linear characteristics can be achieved by tailoring the layers’ amount and grating widths so that the proposed structure can be applicable for several optical applications. Moreover, we demonstrate the switching/bistability behaviors of the MDG at Fano resonance which provide a significant switching intensity reduction compared to the established Lorentzian resonant structures.

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.

Silver nanocolloid as optical bistable device under continue wave laser illuminations

In this study, Kerr effect nonlinearity of silver nanocolloids due to thermal effect is investigated experimentally. Silver nanoparticles are synthesized by chemical reduction method in stable colloidal form in water. The diameter of silver nanoparticles is about 20 nm. Experimental results concerning the optical bistability of the nano-colloid are performed under CW laser illuminations. Two different CW laser beams (He-Ne and Nd-Yag lasers) were used to interact with a vertical Fabry-Perot interferometer containing a cell of nanocolloid. Hysteretic loops are observed due to optical bistability. Furthermore, nonlinear refractive indexes versus incident intensities are evaluated using close aperture z-scan method. It gives more precise values of nonlinear refractive indices that help in numerical drawing of Hysteretic loops. Experiments showed silver nanoparticles have good potential for semi-fast optical switcher devices in both red and green wavelengths.

Optical bistability in shape-memory nanowire metamaterial array

Non-volatile temperature-induced structural phase transitions such as those found in chalcogenide glasses are known to lead to strong changes in optical properties and are widely used in rewritable optical disk technology. Herein, we demonstrate that thermally activated optical memory can be achieved via the nanostructural reconfiguration of a metallic nanowire metamaterial array made from a shape-memory alloy: A nickel-titanium film of nanoscale thickness structured on the subwavelength scale exhibits bistability of its optical properties upon temperature cycling between 30 °C and 210 °C. The structure, comprising an array of NiTi nanowires coated with a thin film of gold to enhance its plasmonic properties, can exist in two non-volatile states presenting an optical reflectivity differential of 12% via nanoscale mutual displacements of alternating nanowires in the structure. Such all-metal shape-memory photonic gratings and metamaterials may find applications in bistable optical devices.

Room temperature operation of electro-optical bistability in the edge-emitting tunneling-collector transistor laser

Optical bistable devices are fundamental to digital photonics as building blocks of switches, logic gates, and memories in future computer systems. Here, we demonstrate both optical and electrical bistability and capability for switching in a single transistor operated at room temperature. The electro-optical hysteresis is explained by the interaction of electron-hole (e-h) generation and recombination dynamics with the cavity photon modulation in different switching paths. The switch-UP and switch-DOWN threshold voltages are determined by the rate difference of photon generation at the base quantum-well and the photon absorption via intra-cavity photon-assisted tunneling controlled by the collector voltage. Thus, the transistor laser electro-optical bistable switching is programmable with base current and collector voltage, and the basis for high speed optical logic processors.

Critical slowing down in an optical bistable model with Kerr-nonlinear blackbody reservoir

We investigate switching response for an Optical Bistable (OB) device consisting of homogeneously broadened two-level atoms in a ring cavity supported by a Kerr Nonlinear Blackbody (KNB) radiation reservoir in the high-Q cavity regime for both absorptive and dispersive cases. In the resonant case and below a transition temperature, faster switching processes for OB devices with KNB can be triggered by a small perturbation of the incident field in the vicinity of the critical transition point. The switching time increases with increasing atomic detuning parameter. A thermal switching process is obtained for a fixed incident field and is triggered by small perturbation in the relative reservoir temperature, Tb say. The switching time is reduced considerably by slightly increasing the temperature Tb. Comparison with other cases of radiation reservoir is made, namely, normal, thermal and squeezed vacuum.

Analysis on optical bistability parameters in photonic switching devices

An investigation has been done on the parameters of a hysteretic bistable optical Schmitt trigger device. From a design point of view, it is important to know the regions where this bistability occurs and is fully functional with respect to its subsystem parameters. Otherwise experimentally reaching such behavior will be very time-consuming and frustrating, especially with multiple devices employed in a single photonic circuit. A photonic Schmitt trigger consisting of two feedbacked inverting amplifiers, each characterized by − m (slope), A ( y -intercept), and B (constant base) parameters is considered. This system is investigated dynamically with a varying input to find its stable and unstable states both mathematically and with simulation. In addition to a complete mathematical analysis of the system, we also describe how m , A , and B can be properly chosen in order to satisfy certain system conditions that result in bistability. More restrictions are also imposed to these absolute conditions by the system conditions as will be discussed. Finally, all results are verified in a more realistic photonic simulation.

Tunable Multiple Fano Resonances in One-Dimensional Photonic Crystal Containing Multiple Superconductor

We investigated the optical properties of one-dimensional photonic crystal composed of multiple different superconductor materials altogether theoretically by transfer matrix method. The number of Fano resonances generated in transmittance spectra depends on the number of different superconductor materials incorporated in the structure of photonic crystal. The Fano resonances are very sharp and sensitive to the varying parameters. The line profile of multiple Fano resonances in transmission spectra can be tuned by varying the thickness of the layers, the angle of incidence, and the temperature of superconductor photonic crystal. The tunable characteristic of multiple Fano resonances has potential application in bistable optical devices, switches, and sensors.

Optical bistability in a nonlinear-shell-coated metallic nanoparticle.

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.

Manipulating the optical bistability at terahertz frequency in the Fabry-Perot cavity with graphene.

We investigate theoretically the optical bistability from a Fabry-Perot cavity with graphene in the terahertz (THz) frequency. It is demonstrated that the optical bistablility in this cavity can be realized due to the electric field enhancement and the giant third-order nonlinear conductivity of graphene. The optical bistable behavior is strongly dependent on the transmission amplitude of the mirror and the position of the graphene in the cavity. It is especially important that the hysterical behaviors of the transmitted light rely on the optical conductivity of graphene, making the Fabry-Perot cavity to be a good candidate for dynamic tunable optical bistable device in the THz frequencies, owing to the possibility of high tunability of graphene conductivity by means of external electrostatic or magnetostatic field.

Low threshold optical bistability at terahertz frequencies with graphene surface plasmons.

We propose a modified Kretschmann-Raether configuration to realize the low threshold optical bistable devices at the terahertz frequencies. The metal layer is replaced by the dielectric sandwich structure with the insertion of graphene, and this configuration can support TM-polarization surface electromagnetic wave. The surface plasmon resonance is strongly dependent on the Fermi-level of graphene and the thickness of the sandwich structure. It is found that the switching-up and switching-down intensities required to observe the optical bistable behavior are lowered markedly due to the excitation of the graphene surface plasmons, thus making this configuration a prime candidate for experimental investigation at the terahertz range. And the switching threshold value can be further reduced by decreasing the Fermi-level or increasing the thickness of sandwich structure, hence providing a new way for realizing tunable optical bistable devices. Finally, the optical bistability at higher terahertz frequency and the influence of relaxation time under the actual experimental condition on Fermi-level are discussed.

Various projective synchronization phenomena in two different variable time-delayed systems related to optical bistable devices

We analytically and numerically analyze the existence of various projective (projective-anticipatory, projective and projective-lag) synchronization between two different modulated time-delayed chaotic systems in this paper. The innovation of our work is that we report on projective-anticipatory and projective-lag synchronization of two different variable time-delayed chaotic systems, while other existing work only mentioned projective synchronization in such systems. Based on the theory of Krasovskii–Lyapunov stability, we derive the sufficient stability condition through theoretical analysis. Mackey–Glass and Ikeda models related to optical bistable or hybrid optical bistable devices are taken for examples to verify the validity and effectiveness of the proposed method.

Controllable optical bistability and multistability in asymmetric double quantum wells via spontaneously generated coherence

We investigate the nonlinear optical phenomena of the optical bistability and multistability via spontaneously generated coherence in an asymmetric double quantum well structure coupled by a weak probe field and a controlling field. It is shown that the threshold and hysteresis cycle of the optical bistability can be conveniently controlled only by adjusting the intensity of the SGC or the controlling field. Moreover, switching between optical bistability and multistability can be achieved. These studies may have practical significance for the preparation of optical bistable switching device.

Analysis of transient response and instability in fiber ring resonators containing an erbium-doped fiber amplifier and quantum dot-doped fiber saturable absorber

In this paper, the transient response of a double coupler fiber ring resonator containing an erbium-doped fiber amplifier (EDFA) in half part of the fiber ring resonator and a quantum dot-doped fiber (QDF) saturable absorber in the other half, is investigated. It is demonstrated that, depending on the device parameters and the input power of the signal and pump, various types of dynamic behaviors (such as bistability, monostability, and regenerative pulsation) can be observed in this intrinsic, optical bistable device. The proposed device can be exploited by optical communication networks to realize all-optical functionalities.

Projective-anticipating, projective and projective-lag synchronization of chaotic systems with time-varying delays

We investigate different types of projective (projective-anticipating, projective and projective-lag) synchronization in unidirectionally nonlinearly coupled time-delayed chaotic systems with variable time delays. Based on the Krasovskii–Lyapunov approach, we find both the existence and sufficient stability conditions, using a general class of time-delayed chaotic systems related to optical bistable or hybrid optical bistable devices. Our method has the advantage that it requires only one nonlinearly coupled term to achieve different types of projective synchronization in time-delayed chaotic systems with variable time delays. Compared with other existing works, our result provides an easy way to achieve projective-anticipating, projective and projective-lag synchronization. Numerical simulations of the Ikeda system are given to demonstrate the validity of the proposed method.

OPTICAL BISTABILITY IN ONE-DIMENSIONAL COUPLED RESONATOR NONLINEAR OPTICAL WAVEGUIDE

In this paper, the optical bistability in finite size one-dimensional coupled resonator nonlinear optical waveguide has been investigated. To calculate the bistable switching manner in five proposed structures, we use the linear and nonlinear transfer matrices with fixed point iteration method. Our results show that the threshold and domain of bistable switching answer depend on the defect region in one-dimensional coupled resonator nonlinear optical waveguides. Also, the best answer of switch takes place at the left and right edges of the photonic band gap of the structures depending on the defect regions. In fact, due to the presence of the photonic band gap in the slow wave system, the density of states of the electromagnetic fields is large at the photonic band edge and photonic defect modes and thus the group velocity is small, and the local field is enhanced. All these factors contribute to a significant decrease in the threshold of optical bistable switching devices.

Performance comparison of all-optical clocked S-R and D type flip-flops

In this paper, different approaches to implement all-optical flip-flops, working with a synchronization signal, will be presented and compared. In this type of optical bistable devices, the information present at the inputs produces effects on the outputs, throughout all the clock pulse period. The performance of optical clocked flip-flops will be studied in terms of extinction ratio (ER), switching energies and switching times.

All-Optical Switches Based on Multiple Cascaded Resonators With Reduced Switching Intensity-Response Time Products

The general nonlinear behavior of multiple cascaded resonators is analyzed by using the coupled-mode theory in time and then compared to a single resonator from the viewpoint of optical bistable operation. Our analysis reveals that from the perspective of switching intensity, the multiple resonator structure is more advantageous than the single resonator with an equivalently increasing quality factor. It is also shown that a switching intensity-response time product, suggested as a performance metric for optical bistable devices, decreases linearly as the number of cascaded resonators increases. The effect of coupling n resonators is equivalent to a single resonator device with n-time increased quality factor in terms of the performance metric. The coupled-mode theory analysis is confirmed by a numerical study of the bistable operation of one-dimensional photonic crystal resonator structures using the finite-difference time-domain method.

Frequency, clockwise to counter clockwise and even to odd lasing mode switching based on optical feedback mechanism

Analyzing modes in a micro-ring waveguide coupled with a feedback resonator reveals that with appropriate parameters, the quality factors of two neighboring ring modes vary periodically and considerably. The effect occurs upon changing the length of the feedback waveguide, whereas the two resonant frequencies remain almost invariant with length change. On the basis of this property, four methods are theoretically demonstrated to realize laser switching: two for frequency switching, one for clockwise to counterclockwise mode switching, and one for even to odd mode switching. The analysis provides methods for bistable lasing and optical logic device design.