Threshold Of Optical Bistability Research Articles

Effect of exceptional point on the performance of a bistable all-optical switch.

Microring cavities based on whispering-gallery modes (WGMs) have a very high-quality factor (Q) and a small mode volume, greatly improving the interaction between light and matter, which has attracted great attention in microlaser, nonlinear, and sensing fields. Plasmonics in the microcavity further enhance compression of the optical field. Recently, research on enhanced optical sensing sensitivity and low threshold laser based on exceptional points (EPs) is quite impressive. In this work, we propose a new, to our knowledge, all-optical switch by using the bistable effect under the EP of an ultra-compact plasmonic racetrack resonator and perform numerical simulations using the finite-difference time-domain (FDTD) method. The introduction of EPs further enhances the localization of the light field and thus improves the Kerr nonlinear effect of the microcavity; low threshold optical bistability is achieved. The results show that the device under an EP has a relatively lower threshold (input optical power threshold of 2.2 MW/cm2), shorter switching time (1.725 ps), and significantly improved switching contrast (17.16 dB) compared with those without EP. Our research lays the groundwork for optical switches that are chip-integrated, have low power consumption, and exhibit short switching times.

Nonlinear Optical Bistability Based on Surface Plasmons with Nonlinear Dirac Semimetal Substrate

In this paper, we theoretically investigated the low-threshold and controllable optical bistability (OB) of a graphene-based Otto configuration with a nonlinear three-dimensional Dirac semimetal (3D DSM) as the substrate. The combined effect of the excitation of surface plasmon polaritons (SPPs) in graphene and the very high third-order nonlinear conductivity of the 3D DSM enabled this scheme to achieve a relatively low optical bistability threshold. At the same time, this simple multilayer structure showed the tunability of OB due to the fact that the reflectance could be modulated by regulating the Fermi energy of the 3D DSM. Furthermore, we also found that the OB hysteresis curve was closely related to the relaxation time of the 3D DSM and the thickness of the air layer. We believe that this multilayer configuration could provide a reference idea for devising a bistable device.

Optical bistability modulation based on graphene sandwich structure with topological interface modes.

In this paper, we have investigated optical bistability modulation of transmitted beam that can be achieved by graphene sandwich structure with topological interface modes at terahertz frequency. Graphene with strong nonlinear optical effect was combined with sandwich photonic crystal to form a new sandwich structure with topological interface modes. The light-limiting properties of the topological interface modes, as well as its high unidirectionality and high transmission efficiency, all contribute positively to the reduction of the optical bistability threshold. In addition, the topological interface modes can effectively ensure the stability of the two steady state switching in the case of external interference. Moreover, optical bistability is closely related to the incident angle, the Fermi energy, the relaxation time, and the number of layers of graphene. Through parameter optimization, optical bistability with threshold of 105 V/m can be obtained, which has reached or is close to the range of the weak field.

Low-temperature optical bistability and multistability in superconducting photonic multilayers with graphene

Optical bistability and multistability are numerically investigated based on periodic superconducting photonic multilayers with graphene in cryogenic environments. Bandgap edge resonances are sensitive to circumstance temperature and can localize the electric field greatly, which is utilized to enhance the nonlinearity of graphene. Consequently, low threshold optical bistability and double-bistability are realized. Optical multistability subsequently arises by increasing the value of circumstance temperature as well. The thresholds of bistability and multistability lower further by decreasing the chemical potential of graphene or promoting the period number of photonic multilayers. The thresholds can be decreased as low as several hundred MW/cm2. The complex structure has a great potential for the development of two- and multiple-valued all-optical switches in low-temperature condition.

Transition from optical bistability to multistability in a tunneling quantum dot via structure hybrid light

In this paper, we proposed a new model based on the electron tunneling effect in a four-level quantum dot molecule (QDM) for studying the optical bistability (OB) and optical multistability (OM). The QDM interacts with a probe and two coupling and Laguerre–Gaussian (LG) fields. We found that by adjusting the electron tunneling effect and the parametric controlling of LG light, the transition from OB to OM or vice versa is possible. Moreover, due to the simultaneous interaction between coupling and LG lights with the same optical transition adjusting the threshold of OB and OM by orbital angular momentum (OAM) of the LG light becomes achievable. Our results show that by adjusting the simultaneous effect of electron tunneling and OAM state of the vortex light, the favorable OB and OM patterns with adjustable intensity thresholds are achievable. Our proposed model may have potential application in quantum information science based on quantum dot (QD) devices.

Tunable Low-Threshold Optical Bistability in Optical Tamm Plasmon Superlattices

We propose a scheme to obtain tunable low-threshold optical bistability of reflected beams in optical Tamm plasmon superlattices (TPS). The low-threshold optical bistability is triggered due to the strong third-order non-linearity of graphene and the local field enhancement in the TPS. Our results show that the optical Tamm plasmon superlattices have the ability to lower the bistable threshold even further than the single optical Tamm state. The results show that the hysteresis behavior and optical bistability threshold can be continuously adjusted by changing the applied voltage and the number of graphene layers (N ≤ 4). In particular, the optical bistability in the TPS is affected by the incident angle. Our results introduce a new possible route for low threshold optical bistability in the THz range and provide a new method in the field of all-optical switching applications.

Low-Threshold Optical Bistability Based on Photonic Crystal Fabry–Perot Cavity with Three-Dimensional Dirac Semimetal

In this paper, we investigate theoretically the tunable low threshold optical bistability (OB) in the terahertz range based on photonic crystals’ Fabry–Perot (FP) cavity with a three-dimensional Dirac semimetal (3D DSM). On the one hand, a 3D DSM with a high nonlinear refractive index coefficient creates conditions for the generation of OB. Additionally, the finite film thickness of 3D DSMs leads to significantly a enhanced interaction volume compared to graphene, which allows easier preparation and has stable properties. On the other hand, the resonance of the FP cavity plays a positive role in promoting the tunable low-threshold OB. It was found that the OB threshold and hysteresis curve can be continuously adjusted by manipulating the Fermi energy and relaxation times of a 3D DSM. Additionally, the bistable curve of the composite structure is also closely related to the angle of incident light. Through parameter optimization, OB with a threshold approaching 105 V/m can be obtained. The photonic crystal’s FP cavity with a 3D DSM structure provides a feasible way to achieve low-threshold OB and a building block for future integrated all-optical devices.

Magnetically tunable ultralow threshold optical bistability by exciting LRSPR in InAs/graphene layers at the terahertz region.

With the experimental corroboration employing a transfer matrix method, an analytical observation of optical bistability using long-range surface plasmon resonance (LRSPR) through the external magnetic field is presented for a very low threshold value. The proposed analytical method has been verified with the reported experimental data provided by Liu etal. [Curr. Appl. Phys.29, 66 (2021)1567-173910.1016/j.cap.2021.06.003]. Now theoretical analysis is further extended in the proposed multilayered structure comprising an InAs layer sandwiched between two graphene layers, whose electromagnetic response at 2THz can be regulated by employing a magnetic field and may tune the optical bistability without modifying the geometry or the characteristics of the structure. The observed threshold intensity for the switch-up is 6.6615×104 W/c m 2 at 0.001T; thus, this analytical approach is able to achieve 2 orders lower threshold for magnetically tunable upswitching of the optical bistable process. This suggested magnetically adjustable optical bistable arrangement gives a possibility for the comprehension of optical logic gates, optic memory, opto-transistors, and switches at a low switching threshold due to extraordinary features of the composite layers due to local field amplification of the graphene layer.

All-optical control of optical bistability in a hybrid system

In this paper, we study the tunneling induced optical bistability (OB) in a quantum dot (QD)-metallic nanoparticle (MNP) hybrid system via surface plasmon effects. We realized that in the presence of the tunneling effect, OB arises when the probe light is parallel to the major axis of the hybrid system. We realized the threshold of OB can be controlled by controlling the distance parameter between the QD and MNP. For appropriate distance between the QD and MNP, we find that optical multistability (OM) appears in the system. We find that the threshold of OM can be adjusted when we consider the radius effect of the MNP, respectively.

Optical bistability and multistability via electron injection rate in an imperfect cavity

In this letter, we investigate the electron injection rate-based optical bistability (OB) and optical multistability (OM) features in an imperfect cavity. Coherent optical fields interact with the open four-level quantum system that makes up the ring cavity. We have discovered that the threshold of OB and OM as well as the length of the hysteresis loop can be changed by varying the length of the quantum system, reflection and transmission coefficient of cavity mirrors. Our findings further show that the electronic exit rate from the cavity and the electron injection rates have a significant impact on the threshold of OB and OM. It is discovered that transitioning from OB to OM or vice versa is achievable by adjusting the controllable parameters. The impact of the cooperation parameter on the properties of the OB and OM is then addressed. The findings demonstrate that the OB features are simple to manipulate. Our suggested model might be used to develop an all-optical device for use in upcoming quantum information processing.

Dirac semimetals Tamm plasmons-induced low-threshold optical bistability at terahertz frequencies

In this paper, we theoretically study the optical bistability (OB) of reflected beams in a composite multilayer structure with three-dimensional Dirac semimetals (3D DSMs) and one-dimensional photonic crystal (1D PC) on both sides of the spacer layer. The optical Tamm states (OTSs) excited by the 3D DSMs-1D PC multilayer structure significantly enhances the local electric field near the nonlinear 3D DSMs, which provides a positive condition for the realization of low threshold OB. Through parameter optimization, we obtain a threshold electric field with an incident electric field of 106 V/m levels. Furthermore, the influences of the Fermi energy of 3D DSMs, the angle of the incident light and dispersion characteristics of the spacer layer on the hysteretic behavior and the threshold of OB are clarified. We believe above results will provide possible options for nonlinear optical bistable devices.

Tunable optical bistability based on Bloch surface waves in one-dimensional photonic crystal with graphene

Graphene possesses large nonlinear conductivity in terahertz region, which makes it a very promising material for nonlinear bistable devices. In this paper, we theoretically study the optical bistability (OB) of reflected beam in a multilayer structure with graphene embedded between the truncated layer and the substrate. The Bloch surface wave excited by the one-dimensional photonic crystal (1D PC) coupling structure significantly enhances the local electric field near the nonlinear graphene, which provides a positive condition for the realization of low-threshold OB. Through parameter optimization, we obtain a threshold electric field with an incident electric field of 105 V/m levels. Furthermore, the influences of graphene’s Fermi energy and relaxation time, as well as those of the incidence angle, on the hysteretic behavior and the threshold of OB are clarified. This approach may provide a feasible scheme for the nonlinear optical bistable devices.

Low threshold optical bistability based on topological edge state in photonic crystal heterostructure with Dirac semimetal.

The special band structure of three-dimensional Dirac semimetal (3D DSM) makes it show strong nonlinear optical characteristics in the terahertz region, which provides a new way to develop terahertz nonlinear devices with low threshold. In this paper, we theoretically study the optical bistability (OB) of transmitted light in a multilayer structure with 3D DSM embedded in two one-dimensional photonic crystals (1D PhC). The topological edge state (TES) excited by the 1D PhC heterostructure significantly enhances the local electric field near the nonlinear 3D DSM, which provides a positive condition for the realization of low threshold OB. Through parameter optimization, we obtain a threshold electric field with an incident electric field of 106 V/m levels. Furthermore, the influences of the Fermi energy and thickness of 3D DSM and the angle of the incident light on the hysteretic behavior as well as the threshold of OB are clarified. 3D DSM-based optical devices with intrinsic OB provide a building block for future integrated optical and all-optical networks.

Low threshold optical bistability in dielectric coated graphene-dielectric-graphene multilayer structure

We propose a dielectric coated graphene-dielectric-graphene multilayer structure and study the input-output property of the structure. Using the boundary conditions of electromagnetic fields at all interfaces, the analytical expression of transmitted field as a function of the incident field is obtained. The optical bistability and multistability are found, and the influence of cladding layer and Fermi energy of graphene on bistability is discussed. We find that the low threshold is obtained by adjusting cladding layer. A reduction by two orders of magnitude in the threshold compared with the no cladding layer case. • A dielectric coated graphene-dielectric-graphene multilayer structure is proposed. • A low threshold is obtained by adjusting cladding layer and Fermi energy. • The threshold is reduced by two orders comparing to the case without cladding layer.

Broadband and Ultra-Low Threshold Optical Bistability in Guided-Mode Resonance Grating Nanostructures of Quasi-Bound States in the Continuum.

We model optical bistability in all-dielectric guide-mode resonance grating (GMR) nanostructures working at quasi-bound states in the continuum (BICs). The complementary metal-oxide-semiconductor (CMOS) compatible material silicon nitride (SiN) is used for the design of nanostructures and simulations. The ultra-low threshold of input intensity in the feasible nanostructure for nanofabrication is obtained at the level of ~100 W/cm2 driven by quasi-BICs. Additionally, the resonance wavelength in the GMR nanostructure can be widely tuned by incident angles with the slightly changed Q-factor that enables the optical bistable devices to work efficiently over a wide spectrum. The impact of the defects of grating that may be introduced in the fabrication process on the optical properties is discussed, and the tolerance of the defects to the optical performance of the device is confirmed. The results indicate that the GMR nanostructures of broadband and ultra-low threshold optical bistability driven by quasi-BICs are promising in the application of all-optical devices.

Low threshold optical bistability in graphene/waveguide hybrid structure at terahertz frequencies

Here we propose a planar graphene/dielectric multilayer configuration to realize low threshold optical bistability at terahertz frequencies. This low-threshold optical bistability is achieved by field enhancement owing to the couple of the surface plasmon polaritons and the planar waveguide mode. We discussed the influence of graphene sheets and planar waveguide mode on the hysteretic response of the TM-polarization reflected light. It is found that the switch-up and switch-down threshold electric fields required to observe the optical bistable behavior are affected markedly by the excitation of surface plasmon polaritons or planar waveguide mode. Besides, the switching threshold value can be further reduced by coupling the surface plasmon polaritons and planar waveguide mode, hence providing a way of realizing low threshold and tunable optical bistable devices.

Theoretical Study of Polarized Optical Bistability Due to Rydberg State in a Four-Level Atomic System under External Magnetic Field

In this paper, we proposed a model based on Rydberg atoms for controlling the optical bistability (OB) and optical multistability (OM) in a ring cavity. The atoms interact with an elliptical polarized probe light and a strong coupling light in the presence of external magnetic field. We realized that the threshold of OB can be controlled by elliptical polarized parameter when the first excited states of the atoms interact with Rydberg state. Also, we found that by adjusting the elliptical parameter of probe light, the switching from OB to OM is possible when we consider the strong coupling between Rydberg level and first excited state of the atomic system. We find that when the probe light becomes linearly the OB and OM disappear due to Rydberg electromagnetically induced transparency. However, by adjusting the polarized parameter of the probe light the threshold of OB can be controlled due to Rydberg electromagnetically absorption. Our proposed model can be used as an all-optical device for switching between OB and OM with potential applications in optical communication.

Low threshold optical bistability based on coupled graphene Tamm states

The optical bistability based on an asymmetric dielectric Bragg reflector (DBR)–graphene–DBR (ADGD) structure is investigated numerically in terahertz frequencies. The threshold of optical bistability can be significantly reduced due to the strong enhancement of localized light field for the coupling between the Tamm states on the two sides of graphene. The threshold value of ADGD is nearly an order of magnitude lower than that in a structure based on graphene–DBR, and can be further reduced by decreasing the Fermi energy of graphene. The results will be helpful for the application of bistable devices in THz range.

Low-Threshold and Tunable Optical Bistability Based on Topological Edge State in One-Dimensional Photonic Crystal Heterostructure With Graphene

In this article, we present a theoretical analysis of the optical bistability phenomenon of the transmitted light beam in a graphene-based one-dimensional photonic crystal heterostructure in terahertz frequency range. This low-threshold optical bistability originates from the enhancement of the local electric field owing to the excitation of topological edge state at the interface between the two proposed one-dimensional photonic crystals. The results of calculation and simulation show that the hysteretic behavior and the threshold of optical bistability can be adjusted continuously by changing the applied voltage of the graphene. Moreover, the optical bistability of this structure also can be modified by the angle of the incident light and the number of graphene layers. Our findings provide a new method for realizing low threshold and tunable optical bistability in terahertz range, indicating excellent application prospects in the field of all-optical switches and other optical bistable devices.

Long-range Graphene Surface Plasmon Polariton induced Tunable Optical Bistability in Terahertz Range

An idea towards the low threshold optical bistability and tunability of bistable thresholds at THz frequency under realistic situation is analyzed through a proposed multilayered configuration. The proposed configuration comprises a coupling prism of silicon, and monolayer graphene sheets spatially separated through 35 nm thick polymer which is sandwiched between an air gap of thickness 4.6 μm and a kerr polymer (GaAs) at 300 K temperature and at an incident light frequency of 2 THz. Utilizing the large nonlinear effect of the configuration obtained by the nonlinearity of the kerr polymer and the high local field effect due to long-range graphene surface plasmon resonance, the switching-down and switching-up threshold values for optical bistability have been markedly reduced upto 1.21×105 V/m and 1.24×105 V/m respectively thereby rendering a minimum threshold intensity of 7.2 kW/cm2 than the articles reported till date. Tunability of the switching-down and switching-up threshold values have also been realized from 1.21×105 V/m to 5.18×105 V/m and 1.24×105 V/m to 1.424×106 V/m respectively through electrical or chemical modification of the charge carrier density and hence fermi energy of the graphene from 0.23 eV to 0.41 eV and from 1.21×105 V/m to 1.56×105 V/m and 1.24×105 V/m to 2.12×105 V/m respectively for the variation in incident angle from 70° to 88°. The effect of damping rate of graphene on optical bistability behavior has also been observed. Therefore the proposed optical bistable configuration finds potential applications in the field of all-optical switching, optical transistor, optical logic, nano-illumination and optical memory with low input threshold at THz frequency and can also be used to realize tunable optical bistable device for future THz optical communication technology.