Influence of Fano interference and incoherent processes on optical bistability in a four-level quantum dot nanostructure

Role of Fano interference and incoherent pumping field on optical bistability in a four-level designed In Ga N/Ga N quantum dot nanostructure embedded in a unidirectional ring cavity are analyzed. It is found that intensity threshold of optical bistability can be manipulated by Fano interference. It is shown that incoherent pumping fields make the threshold of optical bistability behave differently by Fano interference. Moreover, in the presence of Fano interference the medium becomes phase-dependent. Therefore, the relative phase of applied fields can affect the behaviors of optical bistability and intensity threshold can be controlled easily.     

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 4.4 nm to 14.4 nm 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.     

Optical bistability in a defect slab with a negative refractive quantum dot nanostructure

We demonstrate optical bistability (OB) in a defect slab doped V-type four-level InGaN/GaN quantum dot nanostructure in the negative refraction frequency band. It has been shown that the OB behavior of such a quantum dot nanostructure system can be controlled by the amplitude of the driving fields and a new parameter for controlling the OB behavior as thickness of the slab medium in the negative refraction band. Meanwhile, we show that the negative refraction frequency band can be controlled by tuning electric permittivity and magnetic permeability by the amplitude of the driving fields and electron concentration in the defect slab doped. Under the numerical simulations, due to the effect of quantum coherence and interference, it is possible to switch bistability by adjusting the optimal conditions in the negative refraction frequency band, which is more practical in all-optical switching or coding elements, and technology based nanoscale devices.     

A Novel Phase Sensitive Quantum Well Nanostructure Scheme for Controlling Optical Bistability

A novel four-level lambda-type quantum well (QW) nanostructure is proposed based on phase sensitive optical bistability (OB) and multistability (OM) with a closed-loop configuration. The influence of controlling parameters of the system on OB and OM is investigated. In particular, it is found that the OB behavior is strongly sensitive to the relative phase of applied fields. It is also shown that under certain parametric conditions, the OB can be switched to OM or vice versa. The controllability of OB/OM in such a QW nanostructure may bring some new possibilities for technological applications in solid-state quantum information science and optoelectronics.     

Optical bistability and multi-stability via voltage-controlled and the rate of incoherent pump in a quantum dot nanostructure

The optical bistability (OB) and optical multi-stability (OM) in a four-level quantum dot molecule are investigated. The effect of tunnel coupling and the rate of incoherent pump on OB are then discussed. It is found that the OB threshold can be controlled via tunnel coupling and the rate of incoherent pump. We demonstrate that the voltage-controlled detuning can significantly affect the behavior of OB and OM, therefore the OM converts to OB only by the rate of incoherent pump. The results obtained can be used for the development of new types of nanoelectronic devices for realizing switching process.     

Optical bistability and multistability via double dark resonance in graphene nanostructure

Electrons in graphene nanoribbons can lead to exceptionally strong optical responses in the infrared and terahertz regions owing to their unusual dispersion relation.Therefore,on the basis of quantum optics and solid-material scientific principles,we show that optical bistability and multistability can be generated in graphene nanostructure under strong magnetic field.We also show that by adjusting the intensity and detuning of infrared laser field,the threshold intensity and hysteresis loop can be manipulated efficiently.The effects of the electronic cooperation parameter which are directly proportional to the electronic number density and the length of the graphene sample are discussed.Our proposed model may be useful for the nextgeneration all-optical systems and information processing based on nano scale devices.     

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.     

Phase-dependent optical bistability and multistability in a semiconductor quantum well system

We theoretically investigate the hybrid absorptive-dispersive optical bistability and multistability in a four-level inverted-Y quantum well system inside a unidirectional ring cavity. We find that the coupling field, the pumping field as well as the cycling field can affect the optical bistability and multistability dramatically, which can be used to manipulate efficiently the threshold intensity and the hysteresis loop. The effects of the relative phase and the electronic cooperation parameter on the OB and OM are also studied. Our study is much more practical than its atomic counterpart due to its flexible design and the wide adjustable parameters. Thus, it may provide some new possibilities for technological applications in optoelectronics and solid-state quantum information science.     

Effect of Quantum Interference from Incoherent Pumping Field and Spontaneous Emission on Controlling the Optical Bistability and Multi-Stability

Optical bistability (OB) and optical multi-stability (OM) of a four-level Λ-type atomic system with two fold lower levels inside a unidirectional ring cavity is investigated. The effect of quantum interference arising from spontaneous emission and incoherent pumping on OB and OM is discussed. It is found that the threshold of OB and OM can be controlled by quantum interference mechanisms. In addition intensity of coupling field and the rate of an incoherent pumping field on behavior of OB and OM are then discussed.     

Optical bistability and multi-stability in a four-level atomic scheme

We investigate the optical bistability (OB) and optical multi-stability (OM) in a four-level Y-type atomic system. It is found that the optical bistability can strongly be affected by intensity and frequency detuning of coupling and probe fields. The effect of spontaneously generated coherence on phase control of the OB and OM is then discussed. It has also been shown that the optical bistability can be switched to optical multi-stability just by the quantum interference mechanism and relative phase of applied fields.     

Optical bistability induced by quantum coherence in a negative index atomic medium

Bistability behaviors in an optical ring cavity filled with a dense V-type four-level atomic medium are theoretically investigated. It is found that the optical bistability can appear in the negative refraction frequency band, while both the bistability and multi-stability can occur in the positive refraction frequency bands. Therefore, optical bistability can be realized from conventional material to negative index material due to quantum coherence in our scheme.     

Phase control of Goos-Hänchen shifts in a four-level quantum dot nanostructure

In this letter, phase control of the Goos-Hänchen shifts of the reflected and transmitted probe light beams through a cavity containing four-level InGaN/GaN quantum dot nanostructure is theoretically discussed. In order to achieve the wave functions and their corresponding energy levels of the mentioned quantum dot nanostructure, Schrödinger and Poisson equations must be solved in a self consistent manner for carriers (here electron) in quantum dot. It is found that the coupling field, the pumping field as well as the cycling field can enhance the GH shifts of the reflected and transmitted probe beams. The effect of relative phase and the detuning of the probe light on the GH shifts of the reflected and transmitted probe beams are also investigated. We find that the GH shifts can be switched between the large positive and negative values by adjusting the controllable parameters.     

Controlling the optical bistability via interacting dark-state resonances

We analyze the behavior of optical bistability in a four-level mercury atomic system driven by a cavity and two external coherent fields by means of a unidirectional ring cavity. We find that without interacting dark resonances and for large intensity of coupling field, the optical bistability disappears. So, the double dark resonances could significantly establish the optical bistability. Moreover, we demonstrate that the double dark resonances can dramatically reduce the threshold of optical bistability.     

Optical bistability through the cavity effect in a four-level open atomic medium

The optical bistability and multistability behavior in a ring cavity for the four-level open atomic system, driven by two coupling fields has been analyzed. It is shown that the presence of exit rate from cavity is having a dominant effect on generating the optical bi(multi) stability on the system. It is found that the effects of the injection rates can be used to control the threshold intensity. It is also found that optical bistability can convert to optical multistability or vice versa via the effect of intensity and detuning of the coupling fields.     

利用腔内四能级原子相干效应实现全光学信号存储

在光学腔与四能级原子组成的非线性光学双稳系统中，利用调谐于不同能级附近的控制信号光脉冲可以使光学腔模产生“IT”或“负”的非线性相移，从而实现了光学双稳迟滞曲线的受控移动及双稳“高态”与“低态”之间的可控跃变，基于上述效应，完成了光学信号的全光存储与腔输出状态的低功率控制开关．这一结果为全光及量子信息处理提供了新的可供利用的物理机制．     

Voltage-controlled storage and retrieval of an infrared-light pulse in a quantum-dot molecule

Dynamic storage and retrieval of a weak infrared (IR)-light pulse are investigated theoretically with feasible parameters in an asymmetric double quantum dot system, a quantum dot molecule (QDM). It is shown that, with a voltage-controlled tunneling, we are able to store and retrieve the IR signal pulse in this three-subband QDM medium by slowly switching off and on the tunneling. The scheme proposed may open up the electrical controllability of quantum optical information storage and retrieval, which is expected to be useful in quantum information science in an asymmetric double quantum dot controlled by voltage.     

Controlling the optical bistability via quantum interference in a four-level N-type atomic system

We investigate the optical bistability (OB) and optical multi-stability (OM) in a four-level N-type atomic system. The effect of spontaneously generated coherence (SGC) on OB and OM is then discussed. It is found that SGC makes the medium phase dependent, so the optical bistability and multi-stability threshold can be controlled via relative phase between applied fields. We realize that the frequency detuning of probe and coupling fields with the corresponding atomic transition plays an important role in creation OB and OM. Moreover, the effect of laser coupling fields and an incoherent pumping field on reduction of OB and OM threshold is then discussed.     

Optical bistability using quantum coherence in a microwave-driven four-level atomic system

The behavior of the optical bistability (OB) is investigated in an optical system which consists of a four-level atomic system with a microwave drive field and an optical cavity. It is found that the optical bistability can be accomplished by adjusting different physical parameters in both steady and transient process. Due to the existence of the microwave drive field, the optical bistability can be also obtained even under weak coherent coupling field condition. Since the intensity and phase of microwave drive field can be conveniently modulated, this optical system provides a new experimental method to test the optical bistability theory.     

Enhanced Cross-Phase Modulation via Phase Control in a Quantum dot Nanostructure

A four-level quantum dot (QD) nanostructure interacting with four fields (two weak near-infrared (NIR) pulses and two control fields) forms the well-known double-cascade configuration. We investigate the cross-phase modulation (XPM) between the two NIR pulses. The results show, in such a closed-loop scheme, that the XPM can be greatly enhanced, while the linear absorption and two-photon absorption (gain) can be efficiently depressed by tuning the relative phase among the applied fields. This protocol may have potential applications in NIR all-optical switch design and quantum information processing with the solid-state materials.     

Control over hysteresis curves and thresholds of optical bistability in different semiconductor double quantum wells

The effects of optical field on the phenomenon of optical bistability(OB) are investigated in a K-type semiconductor double quantum well(SDQW) under various parametric conditions. It is shown that the OB threshold can be manipulated by increasing the intensity of coupling field. The dependence of the shift of OB hysteresis curve on probe wavelength detuning is then explored. In order to demonstrate controllability of the OB in this SDQW, we compare the OB features of three different configurations which could arise in this SDQW scheme, i.e., K-type, Y-type, and inverted Y-type systems. The controllability of this semiconductor nanostructure medium makes the presented OB scheme more valuable for applications in all-optical switches, information storage, and logic circuits of all optical information processing.