Surface plasmon polariton at the interface of dielectric and graphene medium using Kerr effect

We theoretically investigate the control of surface plasmon polariton(SPP) generated at the interface of dielectric and graphene medium under Kerr nonlinearity. The controlled Kerr nonlinear signal of probe light beam in a dielectric medium is used to generate SPPs at the interface of dielectric and graphene medium. The positive, negative absorption, and dispersion properties of SPPs are modified and controlled by the control and Kerr fields. A large amplification(negative absorption) is noted for SPPs under the Kerr nonlinearity. The normal/anomalous slope of dispersion and propagation length of SPPs is modified and controlled with Kerr nonlinearity. This leads to significant variation in slow and fast SPP propagation. The controlled slow and fast SPP propagation may predict significant applications in nano-photonics, optical tweezers, photovoltaic devices, plasmonster, and sensing technology.     

Enhanced Kerr nonlinearity via quantum interference from spontaneous emission

A novel atom configuration is proposed for a giant Kerr nonlinearity in zero linear and nonlinear probe absorption. It is shown that without coherent control field and just by quantum interference of spontaneous emission, a giant Kerr nonlinearity can be obtained.     

Control of light in a quantized four level graphene atomic system via self and cross-Kerr nonlinearity

We investigate self and cross-Kerr nonlinearity in a four level quantized graphene atomic medium. The absorption, dispersion, transmission and subluminal/superluminal behaviors of a probe light field are studied. An amplification of the probe light field is observed in the absorption spectrum. The normal and anomalous slope of dispersion is also investigated at the positive/negative absorption region. It is shown that Kerr nonlinearity invert and enhance the subluminal/superluminal behaviors of the pulse and self-Kerr effect is found to be more subluminal/superluminal as compared to cross-Kerr effect. The results show significant applications in information storage, self and cross phase modulation and lasing without inversion.     

Enhancement of Kerr nonlinearity and its application to entangled state discrimination

In this paper, the recent research on the enhanced Kerr nonlinearity and its application in entangled state discrimination is reported. Two kinds of dynamics, including interacting double dark resonances and spontaneously generated coherence, are presented to enhance the Kerr nonlinearity. The application of Kerr nonlinearity in quantum state discrimination is also discussed. An arbitrary Greenberger-Horne-Zeilinger state can be discriminated using two-photon polarization parity detection which resorts to cross-Kerr nonlinearity between a single-photon qubit and probe field. In addition, a scheme for Greenberger-Horne-Zeilinger state discrimination of matter qubits is also proposed using the dipole induced transparency in a cavity-dipole system.      

Coherent control of Kerr nonlinearity via double dark resonances

A theoretical scheme for enhanced Kerr nonlinearity is proposed in a four-level ladder-type atomic system based on double dark resonances (DDRs). We solve the relevant density matrix equations in steady state and utilize the perturbation theory to obtain the analytical expressions for the third order susceptibility of the atomic system. The influence of system parameters on behavior of the first and third order susceptibilities is then discussed. In particular, it is found that an enhanced Kerr nonlinearity with reduced linear and nonlinear absorption is obtained around zero probe detuning under the slow light condition through proper adjusting the laser field intensity and frequency detuning of driving fields. The dressed state analysis is employed to explain the physical origin of the obtained result. The obtained results may be important for all-optical signal processing and quantum information technology.     

Enhanced Kerr Nonlinearities Caused by Cross Talk Between Optical and Microwave Transitions

We investigate the enhanced Kerr nonlinearities in four-level atomic vapors driven by a coupling, probe and microwave fields. Under the optical one-photon and two-photon resonant conditions, the linear and nonlinear responses of the weak probe field can be modified by the cross talk among optical and microwave transitions. The enhanced Kerr nonlinearity can form bright optical solitons of the probe field.     

Giant Kerr Nonlinearity for Three-Coupled-Quantum-Well Nanostructures

A four level ladder scheme is employed for the realization of slow light large Kerr nonlinear indices in an asymmetric semiconductor three-coupled-quantum-well (TCQW) structure based on intersubband transitions. It is shown that a giant Kerr nonlinearity accompanied with negligible loss can be achieved by properly tuning the intensity of the control fields. A dressed state analysis is given to explain the origin of such a transparency based on slow light enhanced Kerr nonlinearity in this solid medium. In addition, we show that the three-photon detuning plays the important role in enhancing the third-order nonlinearity of the TCQW medium, and may provide new possibilities for technological applications in nonlinear optics and optical switching.     

Polarization phase gate and three-photon GHZ state using coherently enhanced Kerr nonlinearity

We study the nonlinear optical response of a five-level atomic system in the regimes of electromagnetically induced transparency and coherent Raman gain, corresponding to two different schemes of light-atom interaction. Our analytical and numerical results show that greatly enhanced Kerr nonlinearity and efficient cross phase modulation may be achieved between a weak probe field and a weak signal field. The cross phase modulation via Kerr nonlinearity is then exploited toward the realization of a polarization quantum phase gate and the generation of a three-photon GHZ state.     

Observation of large Kerr nonlinearity at low light intensities

We report an experimental observation of large Kerr nonlinearity with vanishing linear susceptibilities in coherently prepared four-level rubidium atoms. Quantum coherence and interference manifested by electromagnetically induced transparency suppress the linear susceptibilities and greatly enhance the nonlinear susceptibilities at low light intensities. The measured Kerr nonlinearity is comparable in magnitude to the linear dispersion in a simple two-level system and is several orders of magnitude greater than the Kerr nonlinearity of a conventional three-level scheme under similar conditions.     

Control of Group Velocity via Spontaneous Generated Coherence and Kerr Nonlinearity

A four-level N-type atomic medium is considered to study the effect of spontaneous generated coherence(SGC) and Kerr nonlinearity on light pulse propagation. A light pulse is propagating inside the medium where each atom follows four-level N-type atom-field configuration of rubidium(85Rb) atom. The atom-field interaction leads to electromagnetically induced transparency(EIT) process. The atom-field interaction is accompanied by normal dispersion and in the presence of SGC and Kerr nonlinearity the dispersion property of the proposed atomic medium is modified,which leads to enhancement of positive group index of the medium. The enhancement of positive group index then leads to slow group velocity inside the medium. A more slow group velocity is also investigated by incorporated the collective effect of SGC and Kerr nonlinearity. The control of group velocity inside a four-level N-type atomic medium via collective effect of SGC and Kerr nonlinearity is the major part of this work.     

Generation of Four-Photon Cluster State with Coherent Light via Cross-Kerr Nonlinearity

We propose two schemes for preparing four-photon cluster state through cross-Kerr nonlinearity. Two coherent fields interact when they enter a nonlinear Kerr medium. If the interaction time is chosen appropriately in each Kerr medium, four-photon cluster state can be generated based on the results of two homodyne detectors in the first scheme. These schemes only use Kerr medium and homodyne measurements on coherent light fields, which can be efficiently made in quantum optical laboratories. In addition, weak cross-Kerr nonlinearity is sufficient. All of the properties make these schemes feasible in experiments.     

Tailoring optical nonlinearities via the Purcell effect

We predict that the effective nonlinear optical susceptibility can be tailored using the Purcell effect. While this is a general physical principle that applies to a wide variety of nonlinearities, we specifically investigate the Kerr nonlinearity. We show theoretically that using the Purcell effect for frequencies close to an atomic resonance can substantially influence the resultant Kerr nonlinearity for light of all (even highly detuned) frequencies. For example, in realistic physical systems, enhancement of the Kerr coefficient by one to two orders of magnitude could be achieved.     

Tunneling induced transparency and giant Kerr nonlinearity in multiple quantum dot molecules

The linear absorption and the Kerr nonlinearity of multiple quantum dots molecules controlled by the tunneling rather than the laser fields are investigated. The tunneling between the dots can induce multiple transparency windows. By varying the energy splitting of the excited states and the tunneling intensity, the width of the tunneling induced transparency windows can be narrowed. Within the narrowed transparency windows, the steep dispersion profile of the probe field makes it possible to enhance the Kerr nonlinearity. Therefore more than one probe fields with different frequencies can acquire giant Kerr accompanied by vanishing absorption simultaneously.     

Control of Group Velocity via Spontaneous Generated Coherence and Kerr Nonlinearity

A four-level N-type atomic medium is considered to study the effect of spontaneous generated coherence (SGC) and Kerr nonlinearity on light pulse propagation. A light pulse is propagating inside the medium where each atom follows four-level N-type atom-field configuration of rubidium (⁸⁵Rb) atom. The atom-field interaction leads to electromagnetically induced transparency (EIT) process. The atom-field interaction is accompanied by normal dispersion and in the presence of SGC and Kerr nonlinearity the dispersion property of the proposed atomic medium is modified, which leads to enhancement of positive group index of the medium. The enhancement of positive group index then leads to slow group velocity inside the medium. A more slow group velocity is also investigated by incorporated the collective effect of SGC and Kerr nonlinearity. The control of group velocity inside a four-level N-type atomic medium via collective effect of SGC and Kerr nonlinearity is the major part of this work.     

Nonlinear optics of coupled semiconductor microcavities

In a coupled microcavity configuration with Kerr optical nonlinearities in the external as well as in the central distributed Bragg reflectors, the energies of the closely spaced doublet of delocalized photon eigenmodes change with increasing light intensity. One beam optical bistability as well as all optical switching in a pump and probe configuration can be realized. The nonlinearity can induce a novel kind of Rabi anticrossing between a photonic mode and a nearly resonating quantum well exciton. Realistic numerical simulations of such effects in AlGaAs based microstructures are presented.     

Theoretical Investigation of Light Transmission in a Slab Cavity via Kerr Nonlinearity of Carbon Nanotube Quantum Dot Nanostructure

In this paper, we discuss the transmission properties of weak probe laser field propagate through slab cavity with defect layer of carbon-nanotube quantum dot (CNT-QD) nanostructure. We show that due to spin-orbit coupling, the double electromagnetically induced transparency (EIT) windows appear and the giant Kerr nonlinearity of the intracavity medium can lead to manipulating of transmission coefficient of weak probe light. The thickness effect of defect layer medium has also been analyzed on transmission properties of probe laser field. Our proposed model may be useful for integrated photonics devices based on CNT-QD for applications in all-optical systems which require multiple EIT effect.     

Enhanced Kerr nonlinearity via atomic coherence in a three-level atomic system

We measure the Kerr-nonlinear index of refraction of a three-level Lambda-type atomic system inside an optical ring cavity. The Kerr nonlinearity is modified and greatly enhanced near atomic resonant conditions for both probe and coupling beams. The Kerr nonlinear coefficient n(2) changes sign when the coupling beam frequency detuning switches sign, which can lead to interesting applications in optical devices such as all-optical switches.     

Controllable Kerr nonlinearity with vanishing absorption in a four-level inverted-Y atomic system

The giant enhancement of Kerr nonlinearity in a four-level inverted-Y atomic system is investigated theoretically. Compared with that generated in a generic three-level system, the Kerr nonlinearity can be enhanced by several orders of magnitude with vanishing linear absorption. The physical mechanism leading to the giant enhancement of Kerr nonlinearity is also discussed.     

Giant Kerr nonlinearity in an n-doped semiconductor quantum well

A scheme for enhancement of Kerr nonlinearity with vanishing linear and nonlinear absorption in a three-level ladder-configuration n-doped semiconductor quantum well is proposed. It is shown that the Kerr nonlinearity can be controlled and even enhance by the intensity of coupling fields. Also, phase control of Kerr nonlinearity is then discussed.     

四能级Tripod-型原子系统中量子相干导致的交叉Kerr非线性效应

计算了四能级Tripod-型原子系统中探针光极化率随其频率失谐量的变化曲线.结果表明,当触发光作用于该系统的一个共振跃迁能级时,可使探针光的吸收和色散在其电磁感应透明(Electromagnetically Induced Transparency,EIT)窗口(由耦合光产生)处发生显著变化.随着触发光Rabi频率的增加,探针光在EIT窗口的吸收显著降低,色散显著增加.这种由触发光引起的探针光极化率的变化对应着三阶Kerr非线性光学效应,这一效应在偏振量子相位门中有着潜在的应用价值.