Cavity Field Spectra of a Cascade Three-Level Atom Interacting with a Single-Mode Field with Kerr-Like Medium

The cavity field spectrum of a cascade three-level atom interacting with single-mode field with Kerr-like medium in the cavity is investigated. The numerical results for the initial field in pure number state, coherent state and squeezed vacuum state are calculated, respectively. It is found that the Kerr-like medium affects the spectral structure even though the initial field is in vacuum when the atom is in upper level. In the case of strong input field, the number state spectrum shows two peaks with different heights; and the superposition state spectrum shows a multipeak structure with an equal distance of two neighboring peaks. The spectral ＂central frequency＂ shifts away from the resonant frequency with the increasing of average photon number.     

Eigenvalue spectrum analysis for temporal signals of Kerr optical frequency combs based on nonlinear Fourier transform

Based on the nonlinear Schr?dinger equation(NLSE) with damping, detuning, and driving terms describing the evolution of signals in a Kerr microresonator, we apply periodic nonlinear Fourier transform(NFT) to the study of signals during the generation of the Kerr optical frequency combs(OFCs). We find that the signals in different states, including the Turing pattern, the chaos, the single soliton state, and the multi-solitons state, can be distinguished according to different distributions of the eigenvalue spectrum. Specially, the eigenvalue spectrum of the single soliton pulse is composed of a pair of conjugate symmetric discrete eigenvalues and the quasi-continuous eigenvalue spectrum with eye-like structure.Moreover, we have successfully demonstrated that the number of discrete eigenvalue pairs in the eigenvalue spectrum corresponds to the number of solitons formed in a round-trip time inside the Kerr microresonator. This work shows that some characteristics of the time-domain signal can be well reflected in the nonlinear domain.     

Entropy evolution properties in a system of two entangled atoms interacting with light field

In this paper, we use the field entropy as a measurement of the degree of entanglement between the light field and the atoms of the system which is composed of two dipole—dipole interacting two-level atoms initially in an entangled state interacting with the single mode coherent field in a Kerr medium. The influence of the coupling constant of dipole—dipole interaction between atoms and the coupling strength of the Kerr medium with the light field and the intensity of the light field on the field entropy are discussed by numerical calculations. It is shown that when the coupling strength of the Kerr medium with the light field is large enough, and the light field is strong, the degree of entanglement between the atoms with the light field becomes weaker. The degree of entanglement only changes slightly with the change of the coupling constant of dipole—dipole interaction between atoms.     

Effect of cavity dissipation on the emission spectrum of an atom interacting with a field in the dispersive approximation

The emission spectrum of a two-level atom interacting dispersively with a single mode radiation field in the dissipative cavity is investigated. A general expression for the emission spectrum is derived. The numerical results for the initial field in coherent state are calculated. It is found that the spectrum structure is influenced significantly by the cavity damping constant \kappa , and the spectrum structure is dependent on the interaction time T when the cavity dissipation is present. Only one peak located at Ω_a appears in the atomic spectra for larger T.     

Dynamics of Entropy and Nonclassicality Features of the Interaction between a ◇-type Four-Level Atom and a Single-Mode Field in the Presence of Intensity-Dependent Coupling and Kerr Nonlinearity

The interaction between a◇-type four-level atom and a single-mode field in the presence of Kerr medium with intensity-dependent coupling involving multi-photon processes has been studied. Using the generalized(nonlinear)Jaynes–Cummings model, the exact analytical solution of the wave function for the considered system under particular condition, has been obtained when the atom is initially excited to the topmost level and the field is in a coherent state. Some physical properties of the atom-field entangled state such as linear entropy showing the entanglement degree, Mandel parameter, mean photon number and normal squeezing of the resultant state have been calculated. The effects of Kerr medium, detuning and the intensity-dependent coupling on the temporal behavior of the latter mentioned nonclassical properties have been investigated. It is shown that by appropriately choosing the evolved parameters in the interaction process, each of the above nonclassicality features, which are of special interest in quantum optics as well as quantum information processing, can be revealed.     

Emission spectrum of a harmonically trapped Λ-type three-level atom

We theoretically investigate the emission spectrum for a Λ-type three-level atom trapped in the node of a standing wave. We show that the atomic center-of-mass motion not only directly affects the peak number, peak position, and peak height in the atomic emission spectrum, but also influences the effects of the cavity field and the atomic initial state on atomic emission spectrum.     

Entropy squeezing and atomic inversion in the h-photon Jaynes-Cummings model in the presence of the Stark shift and a Kerr medium： A full nonlinear approach

The interaction between a two-level atom and a single-mode field in the k-photon Jaynes-Cummings model （JCM） in the presence of the Stark shift and a Kerr medium is studied. All terms in the Hamiltonian, such as the single-mode field, its interaction with the atom, the contribution of the Stark shift and the Kerr medium effects are considered to be f-deformed. In particular, the effect of the initial state of the radiation field on the dynamical evolution of some physical properties such as atomic inversion and entropy squeezing are investigated by considering different initial field states （coherent, squeezed and thermal states）.     

Entropy squeezing and atomic inversion in the K-photon Jaynes–Cummings model in the presence of the Stark shift and a Kerr medium:A full nonlinear approach

The interaction between a two-level atom and a single-mode field in the k-photon Jaynes–Cummings model(JCM) in the presence of the Stark shift and a Kerr medium is studied. All terms in the Hamiltonian, such as the single-mode field, its interaction with the atom, the contribution of the Stark shift and the Kerr medium effects are considered to be f-deformed.In particular, the effect of the initial state of the radiation field on the dynamical evolution of some physical properties such as atomic inversion and entropy squeezing are investigated by considering different initial field states(coherent, squeezed and thermal states).     

Photon statistics of the micromaser with a Kerr medium

We have established the master equation for the micromaser with a Kerr medium,we have studied the photon statics of the micromaser with a Kerr medium field and analysed the influence of the Kerr effect on the photon statistics,The influence of the Kerr effect on the photon statistics is different in two regimes,In the thermal-atom regime,the Kerr effect produces quantum noise,and decreases the mean photon number.In the ultracold-atom regime,with the increase of the nonlinear parameter of the Kerr medium,the stability of the mean photon number and the normalized variance enhances the mean photon number,and the normalized variance exhibits collapse-revival phenomena periodically,their resonance peaks become lower,and the photon statistics of more and more regions are sub-Poissonian.     

Influences of decoherence on the generation of a macroscopic superposition state using weak cross-Kerr effect

Considering a system in which a single photon and a coherent field propagate through a Kerr medium, when the weak cross-Kerr interaction between the coherent state and the single photon under decoherence is involved, this paper derives analytically a macroscopic superposition state by the superoperator method and investigates the influences of decoherence on the coherence properties of the obtained state. It finds that the macroscopic superposition state will experience evolution from a pure superposltion state to a mixed state in a dissipative environment and the Kerr effect makes the field display a periodic revival from decoherence for a short time.     

Effect of the Initial Laser Phase on the Interaction Between Relativistic Electron and Ultra－Intense Laser Field in a Strong Uniform Magnetic Field

We investigate the influence of the initial laser phase on the interaction between relativistic electron and ultraintense linear polarized laser field in a strong uniform magnetic field. It is found that the dynamic behaviour of the relativistic electron and the emission spectrum varies dramatically with different initial laser field phases.The effect of changing initial phase is contrary in the two parameter regions divided by the resonance condition.The phase dependence of the electron energy and velocity components are also studied. Some beat structure is found when the initial laser phase is zero and this structure is absent when the initial laser phase is a quarter of a period.     

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 effciently made in quantum optical laboratories. In addition, weak cross-Kerr nonlinearity is sufficient. All of the properties make these schemes feasible in experiments.     

Spectrum of the Micromaser with Kerr Medium

We have established the master equation for the micromaser with Kerr medium field density operator,studied the spectrum of the micromaser with Kerr medium and analyzed the influence of Kerr effect and the detuning on the spectrum.In the thermal-atom regime,we find that Kerr effect broadens Linewidth D and increases frequency-shift S,and that the detuning Δ narrows linewidth D and increases frequency-shift S as a whole,Moreover Kerr effect leads to oscillatings more rapidly in the resonance peaks,which means that it causes quantum noise,As a whole,with the increase of cavity-length L,the linewidth D and frequency-shift S gradually increase.     

Influence of multi-photon excitation on the atomic above-threshold ionization

Using the time-dependent pseudo-spectral scheme, we solve the time-dependent Schr ¨odinger equation of a hydrogenlike atom in a strong laser field in momentum space. The intensity-resolved photoelectron energy spectrum in abovethreshold ionization is obtained and further analyzed. We find that with the increase of the laser intensity, the abovethreshold ionization emission spectrum exhibits periodic resonance structure. By analyzing the population of atomic bound states, we find that it is the multi-photon excitation of bound state that leads to the occurrence of this phenomenon, which is in fairly good agreement with the experimental results.     

Optical bistability based on surface plasmon coupled between a noble metal film and a metal grating involving Kerr materials

A phenomenon about optical bistability is successfully investigated in a layered structure consisting of a silver film with Kerr medium and a silver grating sandwiched between semi-infinite linear dielectrics.This type of structure can lead to the optical bistability phenomena occurring in reflection and transmission.There exists an optimal thickness of the metal grating that can cut off the effect of the near-field enhancement and may have the lowest effect on conversion from surface plasmon to light.This structure can realize the functions of the beam splitter and the polarization splitter and will be essential for future classical and quantum information processing.     

Entropy squeezing of the field interacting with a nearly degenerate V-type three-level atom

The position- and momentum-entopic squeezing properties of the optical field in the system of a nearly degenerate three-level atom interacting with a single-mode field are investigated. Calculation results indicate that when the field is initially in the vacuum state, it may lead to squeezing of the position entropy or the momentum entropy of the field if the atom is prepared properly. The effects of initial atomic state and the splitting of the excited levels of the atom on field entropies are discussed in this case. When the initial field is in a coherent state, we find that position-entropy squeezing of the field is present even if the atom is prepared in the ground state. By comparing the variance squeezing and entropy squeezing of the field we confirm that entropy is more sensitive than variance in measuring quantum fluctuations.     

Fidelity of quantum information for V-type three-level atom interacting with a number state light field in Kerr medium

In this paper the evolution characteristics of the fidelity of quantum information for the V-type three-level atom interacting with number state light field in Kerr meddium are investigated. It shows that the periodicity of the evolutions of fidelity of quantum information is influenced by the Kerr coefficient, the photon number of the initial field and intensity of light. The evolutions of the fidelity of quantum information are modulated by the initial number state field. The Rabi oscillation frequency and the modulation frequency of fidelity for the field and the system vary with the value of the Kerr coefficient. The evolutions of fidelity of quantum information obviously show the quantum collapse and revival behaviours in the system of atom interacting with light field.     

Localized modes in orientation-disordered one-dimensional media with uniaxial scatterers

Localized modes in one-dimensional (1D) media with uniaxial scatterers that are assumed to be order in spatial location but disorder in spatial orientation of their optical axis are investigated.Based on the holistic effect model in random laser,i.e.,the random laser is due to the interaction of the complex localized modes in active random media with local aperiodic quasi-structure with appropriate pump light,a physical model on this type of random media is found.Its disorder degree is defined by D=n_o/n_e.Then,the typical transmission spectrum through the random media and the light field intensity distribution corresponding to the defect modes in photonic band-gap are calculated numerically by means of the transfer matrix method,and the condition that the localized mode appears is discussed.Results show that the medium disorder plays an important role in determining the lightwave state.The localized state appears when the medium disorder is strong enough,and a new mechanism creating random laser phenomenon is brought forward.     

Gain-assisted optical switching in plasmonic nanocavities

A plasmonic cavity filled with active material is proposed to explain optical switching. Optical properties, including transmission, response time, and field distribution of on/off state, are numerically investigated. We demonstrate that such a gain-assisted plasmonic structure can achieve optical switching in the nan- odomain and shorten the switching time to the subpicosecond level. Our results indicate the potential application of the proposed structure in optical communication and photonic integrated circuits.     

Entanglement properties between two atoms in the binomial optical field interacting with two entangled atoms

The temporal evolution of the degree of entanglement between two atoms in a system of the binomial optical field interacting with two arbitrary entangled atoms is investigated. The influence of the strength of the dipole–dipole interaction between two atoms, probabilities of the Bernoulli trial, and particle number of the binomial optical field on the temporal evolution of the atomic entanglement are discussed. The result shows that the two atoms are always in the entanglement state. Moreover, if and only if the two atoms are initially in the maximally entangled state, the entanglement evolution is not affected by the parameters, and the degree of entanglement is always kept as 1.