Bistability Threshold Research Articles

Optical bistability and multistability in a four-level quantum system in the presence of plasmonic nanostructure

In this paper, the effect of plasmonic nanostructure on behavior of optical bistability and multistability in a four-level quantum system embedded in a unidirectional ring cavity has been studied. It is found that the distance between plasmonic nanostructures and a four-level quantum system is varied from 4.4nm to 14.4nm and has an essential role for controlling the threshold of optical bistability and multistability. Moreover, obtained results show that the group velocity of pulse propagation through the medium is strongly depended on the distance between the plasmonic nanostructure and the four-level quantum system.

Magnetically dependent optical bistability and multistability in open diamond nitrogen-vacancy centers

We have investigated the optical bistability and optical multistability behaviors in a unidirectional ring cavity filled with diamond nitrogen-vacancy (defect centers driven by an elliptically polarized probe field in the presence of magnetic field and compare its properties with the corresponding closed system. Our numerical result demonstrates that threshold of optical bistability and the width of hysteresis loop can be manipulated by adjusting the phase difference between the two circularly polarized components of a single coherent field and cavity parameters, i.e., the electronic exit rate from cavity and electron injection rates. It is also shown that optical bistability and optical multistability are very sensitive to the relative phase between applied fields and magnetic field. It can be realized that by tuning the parameters the transition from bistability to multistability or vice versa can be obtained.

Tunable terahertz bistability with temperature in photonic crystals containing an InSb layer and coupled nonlinear defects

In this paper, we investigate the terahertz bistability behavior in a photonic crystal doped with an InSb layer and coupled nonlinear defects by employing the modified transfer matrix method. It is demonstrated that the switch-up threshold for bistability can be strongly controlled by ambient temperature without changing the structure of photonic multilayer. The switch-up threshold increases with increasing temperature to a certain value. No dramatic changes are observed in switch-down threshold with increasing the ambient temperature. Further increase of temperature from 309 K to 311 K leads to the strong reduction of switch-up threshold. Our results reveal that the switch-up threshold for the case T = 311 K is approximately 3000 times lower than that of the case T = 309 K. This sensitivity to temperature can have potential applications in terahertz devices. When temperature increases from 309 K, both switch-up and switch-down threshold increase. However, the switch-down threshold indicates much smaller changes compared to the switch-up threshold. Furthermore, we investigate the effect of incident angle on the bistability behavior. It is shown that the temperature at which the lowest value of switching powers is achieved depends on the incident angle.

Tunable THz optical bistability in graphene-based heterostructures

We investigate theoretically the THz optical bistability properties of graphene-based heterostructures. We derive a simple procedure to calculate the nonlinear transmission in graphene-based heterostructures. It is found that the hysteretic response occurs when the frequency of the incident light is less than critical frequency. Compared with the traditional nonlinear materials, THz optical bistability can be tuned more effectively in the proposed structure. It is shown that the optical bistability can be electrically controlled via suitably varying the applied voltage on the graphene, and can also be tuned by adjusting incident angle, the frequency of the incident light, and the refractive index of the constituent materials. The bistable thresholds can be lowered markedly by decreasing the Fermi energy or incident angle.

Phase control of optical bistability in an InGaN∕GaN quantum dot nanostructure

In this paper, we propose a model for controlling the optical bistability in four-level [Formula: see text] quantum dot nanostructure which is embedded in a unidirectional ring cavity. [Formula: see text] quantum dot nanostructure is based on our recent paper [S. H. Asadpour, Z. Golsanamlou and H. R. Soleimani, Physica E 54 (2013) 45]. It is found that intensity threshold of optical bistability can be manipulated by signal intensity of applied fields. Moreover, we find that phase variation of terahertz signal field can also affect the behaviors of optical bistability and hysteresis loop.

A tunable bistable device based on a coupled quantum dot–metallic nanoparticle nanosystem

We theoretically propose a scheme of a tunable bistable device based on a coupled semiconductor quantum dot–metal nanoparticle nanosystem in the simultaneous presence of a strong pump laser and a weak probe laser with different frequencies. The results show that it is easy to turn on or off the optical bistable effect in such system by switching the polarization direction of the pump field, and the bistability thresholds are highly sensitive to the intensity, frequency, polarization direction of the pump field, and the interparticle distance. In addition, the nonlinear absorption in the two stable states exhibits a ratio as high as 104 arising from the three-photon effect, which implies that our nanosystem can also be used as an optical memory cell.

Tunable optical bistability of dielectric/nonlinear graphene/dielectric heterostructures.

We have established the theoretical relation of nonlinear optical response with respect to the dielectric/nonlinear graphene/dielectric heterostructures and further demonstrated the tunable optical bistability at terahertz frequencies. It is shown that the hysteretic behavior is strongly dependent on the Fermi energy of graphene, and the threshold electric fields could be correspondingly adjusted with the continuous tuning of Fermi Energy level. It is clear that the bistable thresholds can be lowered dramatically by decreasing the Fermi energy of graphene, at the same time the optical hysteresis width is narrowed. Moreover, we have confirmed that the optical bistability can be tuned by adjusting the incident illumination angle, or by varying the thickness and permittivity of the dielectric slabs. Our contribution might provide a new avenue of fabricating graphene based optical switching device that could even operate at terahertz regime.

Controlling the optical bistability via quantum interference of incoherent pump in a four-level atomic system

Optical bistability is investigated in a four-level atomic system via direct and indirect incoherent pump fields. The threshold of optical bistability has substantially been decreased by the rate of direct and indirect incoherent pump processes. In addition, quantum interference of spontaneous emission and incoherent pump field affect the bistabile behavior of the medium.

Investigating the impact of correlated white noises on the bistability behavior in an optical three-level bistable system

The effect of correlated white noises on the optical bistability behavior of three-level atomic systems is theoretically investigated. Noise-induced bistability is demonstrated in an atomic optical bistable system consisting of three-level atoms in Λ-type configurations confined in an optical ring cavity. The output field as a result of enhanced Kerr nonlinearity induced by atomic coherence in the electromagnetically induced transparency system is variable due to the noises in laser parameters and the cooperativity parameter. Therefore, noise is mainly responsible for such induced bistability in the system. It is found that with the cross-correlation noises, the hysteresis loop of optical bistability can be clearly expanded in comparison with the deterministic case and the atomic system could show multistability behavior. This is specifically considerable for positive cross-correlated noises where it could expand the domain of the hysteresis loop. In the presented atomic system the numerical result shows that noise can induce bistability in the absence of spontaneously generated coherence. Furthermore, it is salient that the noise could induce bistability when the system is below its deterministic threshold for bistability.

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.

Permanent dipole moment induced stability and group index switching in a three-level molecule

The effect of permanent dipole moments on the optical bistability of weak probe light in a unidirectional ring cavity with a three-level molecule is investigated. It is found that the intensity threshold of optical bistability and optical multistability can be controlled by quantum coherence induced by permanent dipole moments. It is shown that switching from optical bistability to optical multistability and lasing without population inversion can be occurred by this coherence under different conditions.

Optical bistability via Josephson coupling energy in a superconducting quantum circuit

A novel configuration is proposed to study optical bistability (OB) and optical multistability (OM) in a superconducting quantum circuit with a tunable V-type artificial molecule constructed by two superconducting Josephson charge qubits coupled with each other through a superconducting quantum interference device. We find that the ratio of the Josephson coupling energy to the capacitive coupling strength has a significant impact on creating optical bistability. The influence of other system parameters on bistable behavior of the artificial medium is then discussed. In particular, it is found that applying an incoherent pumping field can noticeably reduce the bistable threshold. We also realize a switch from OB to OM through proper tuning of detuning parameters. The controllability of OB and OM of this artificial molecule may be useful in building logic-gate devices for optical computing and quantum information processing and provide some new possibilities for solid-state quantum information science.

Optical bistability with hybrid silicon-plasmonic disk resonators

Optical bistability with a hybrid silicon-plasmonic configuration consisting of a nonlinear traveling-wave (disk) resonator side-coupled with a bus waveguide is theoretically investigated. The nonlinear response is studied with a theoretical framework combining perturbation theory and temporal coupled-mode theory. For the CW case, a general closed-form expression is derived. The effect of the parameters entering in the expression on the bistability curve is thoroughly investigated, and the physical system is accordingly designed so as to exhibit minimum power threshold for bistability and maximum extinction ratio between bistable states. Finally, the temporal dynamics are assessed. The system can toggle between bistable states in approximately 5 ps and is thus suitable for ultrafast memory and switching applications.

Role of Er3+ ion concentration and incoherent pumping field on optical bistability in Er3+:YAG crystal

In this paper, two atomic models are proposed in an 35 nm Er3+-doped YAG crystal. The effect of Er3+ ion concentration and incoherent pumping field on optical bistability is discussed. The results for two models show that the threshold of optical bistability for some Er3+ concentration reduces and for some concentration increases. We display that the incoherent pumping field makes the behavior of optical bistability for two proposed model completely different at identical conditions for Er3+ concentration. Our results show that in the absence and presence of incoherent pumping field some Er3+ concentration can lead to maximum and minimum OB threshold. We hope that our proposed model can be suitable for optimizing and controlling the optical bistability in Er3+:YAG crystal.

Comparison of optical properties between ladder and lambda-type EIT medium with Er3+ ion concentration in Er3+:YAG crystal

The effect of Er3+ doped ion concentration on optical properties of two type three-level schemes in 35 nm Er3+:YAG (yttrium aluminum garnet) crystal is studied. It is found that intensity threshold of optical bistability and multistability can be changed by Er3+ doped ion concentration. Moreover, switching from optical multistability to optical bistability can be done differently by Er3+ concentration in two types of three-level schemes. The steady-state and transient behaviors of absorption, dispersion and group index of weak probe field in two schemes are also discussed. In this study, we will report an initial study on optical properties in Er3+:YAG crystal and propose a basis for selecting the suitable concentration to carry out experimental investigations in the future.

Controlling the optical bistability in a three-level quantum-dot molecule via gate voltage and indirect incoherent pump field

Modification of the optical bistability (OB) in an asymmetric double quantum dot (QD) molecule is investigated via interdot tunnel coupling. It is shown that the bistable threshold intensity can efficiently be controlled by tuning the system parameters such as the gate voltage and indirect incoherent pump rate. This may be employed for the development of new types of nanoelectronic devices for realizing switching process.

Tunable optical bistability at the graphene-covered nonlinear interface

We investigate theoretically the optical bistability of reflection at the interface between graphene and Kerr-type nonlinear substrates. We derive a simple procedure to calculate the nonlinear reflectivity with graphene, and discuss the influence of the graphene sheets on the hysteretic response of the TM-polarization reflected light. It is found that the bistable behavior of the reflected light can be electrically controlled via suitably varying the applied voltage on the graphene. In THz, the bistable thresholds can be lowered markedly by increasing the Fermi energy. However, in near-infrared frequency, it requires multiple graphene layers to exhibit significant influence on the bistable thresholds.

The effect of magnetic field on bistability in 1D photonic crystal doped by magnetized plasma and coupled nonlinear defects

In this work, we study the defect mode and bistability behavior of 1-D photonic band gap structure with magnetized plasma and coupled nonlinear defects. The transfer matrix method has been employed to investigate the magnetic field effect on defect mode frequency and bistability threshold. The obtained results show that the frequency of defect mode and bistability threshold can be altered, without changing the structure of the photonic multilayer. Therefore, the bistability behavior of the subjected structure in the presence of magnetized plasma can be utilized in manufacturing wide frequency range devices.

Power-free bistable threshold accelerometer made from a carbon nanotube framework

Abstract. This paper presents a design and a method for fabricating and testing fully compliant, bistable threshold accelerometers made from a carbon-infiltrated carbon nanotube framework. Two different configurations based on differences in compliant beam angles are presented. Both configurations were tested under constant accelerations produced by mounting them on a spinning disk and under impulse accelerations by mounting them to the end of a swinging pendulum with a stop at the lowest point of the pendulum path. Tests were also performed to observe the potential effects of stress relaxation in the carbon nanotube material. This was done by placing the accelerometers in their second stable position (nonfabricated position) and then testing them after a period of 24 h. Results show that in eight of the twelve tests there was no significant change due to stress relaxation. In the other four tests, the change was relatively small, especially when compared to stress relaxation effects in other materials such as plastics. Measurements indicate that the accelerometers show very high repeatability individually. However, we also observed that there is significant variation in switching acceleration between accelerometers with identical geometric parameters. This may be due to random variation occurring during the fabrication process.

Optical Bistability and Multistability in an EIT Medium with Two-Photon Resonance Transitions

Intensity threshold of optical bistability (OB) and optical multistability (OM) can be controlled by amplitude and phase control of microwave driven field in the two-photon resonance transitions in a parametric region. It is found that in two-photon resonance case, the weak microwave field can reduce the threshold of optical bistability and strong microwave field can lead to optical multistability. The effect of relative phase between applied fields is also discussed. It is shown that for weak and strong microwave field, intensity threshold of OB and OM can be modified. Moreover, it is found that for strong microwave field, relative phase has an essential role for switching between OB and OM or vice versa.