Dynamics of Two-Photon Lasers with A Atomic Level Configuration

We derive the dimensionless dynamic equations of two-photon lasers with A atomic level configuration by using the quantum Langevin equation method with the considerations of atomic coherence and injected classical fields. Then we analyze the stability and the chaotic dynamics of the two-photon laser by calculating the bifurcation diagram and the maximum Lyapunov exponent （MLE）. Our results show that the Lorenz strange attractors and one-focus strange attractors can exist in this system, and the chaos can be induced or inhibited by the injected classical fields via Hopfbifurcations or crises, while the atomic coherence induces chaos via crises, and inhibit chaos via Hopf bifurcation or crises.     

Resonance Fluorescence in Two—Photon JC Models Analyzed by Supersymmetric Transformation

Resonance fluorescences of two-photon two-level and two-photon three-level atoms driven by laser are investigated with supersymmetric transformation.It is shown that the spectrum of fluorescent light obtained from the supersymmetric transformation is more accurate and the physical process shown by this method is clearer than that from dress transformation.     

Quantum—Mechanical Simulation of an Atomic Beam Focused by an Optical Standing Wave

Recent experiments have demonstrated that the light pressure force from an optical standing wave (SW) focuses an atomic beajm to sub-micrometre dimensions.We start from a two-dimensional time-dependent Schrodinger equation and reduce in to a one-dimensional equation by a paraxial approximation.We calculate some theoretical limits on the focusing of an atomic beam by an SW optical field.It is found that two parameters,the atomic velocity and the intensity of the laser beam,play an important role in determining the deposition quality.     

Husimi Operator for Describing Probability Distribution of Electron States in Uniform Magnetic Field Studied by Virtue of Entangled State Representation

For the first time we introduce an operator Δ _h (γ,ε;κ) for studying Husimi distribution function in phase space (γ,ε) for electron’s states in uniform magnetic field, where κ is the Gaussian spatial width parameter. The marginal distributions of the Husimi function are Gaussian-broadened version of the Wigner marginal distributions. Using the Wigner operator in the entangled state 〈λ | representation we find that Δ _h (γ,ε;κ) is just a pure squeezed coherent state density operator | γ,ε〉 _{κ κ} 〈γ,ε |, which brings much convenience for studying Husimi distribution, so we name Δ _h (γ,ε;κ) the Husimi operator. We then derive Husimi operator’s normally ordered form that provides us with an operator version to examine various properties of the Husimi distribution. Work supported by the National Natural Science Foundation under the grant: 10775097.     

Self—Trapping State and Atomic Tunnelling Current of an Atomic Bose—Einstein Condensate Interacting with a Laser Field in a Double—Well Potential

We present a theoretical treatment of dynamics of an atomic Bose-Einstein condensation interacting with a single-mode quantized travelling-wave laser field in a double-well potential.When the atom-field system is initially in a coherent state,expressions for the energy exchange between atoms and photons are derived.It is revealed that atoms in the two wells can be in a self-trapping state when the tunnelling frequency satisfies two specific conditions,in which the resonant and far off-resonant cases are included.It is found that there is an alternating current with two different sinusoidal oscillations between the two wells,but no dc characteristic of the atomic tunnelling current occurs.It should be emphasized that when without the laser field,both the population difference and the atomic tunnelling current are only a single oscillation.But they will respectively become a superposition of two oscillations with different oscillatory frequencies in the presence of the laser field.For the two oscillations of the population difference,one always has an increment in the oscillatory frequency,the other can have an increment or a decrease under different cases.These conclusions are also suitable to those of the atomic tunnelling current.As a possible application,by measurement of the atomic tunnelling current between the two wells,the number of Bose-condensed atoms can be evaluated.By poperly selecting the laser field,the expected atomic tunnelling current can be obtained too.     

Transmission Probability of an Ultracold Atom in the Presence of Atomic Coherence

We investigate the transmission probability of an ultracold V-type three-level atom passing through a micromaser cavity,in the presence of atomic coherence which is established by a coherent driving field.We show that the transmissibility of this micromaser system with the atomic coherence is better than that of the ordinary micromaser system without atomic coherence.When the driving field is strong enough,for any cavity length the ultracold atom can pass through the micromaser cavity freely.     

Resonance-Radiation Force Exerted by a Circularly Polarized Light on an Atomic Wave Packet

We study the behaviour of an atomic wave packet in a circularly polarized light, and especially give the calculation of the radiative force exerted by the circularly polarized light on the atomic wave packet under the resonance condition. A general method of the calculation is presented and the result is interesting. For example, under the condition that the wave packet is very narrow or/and the interaction is very strong, no matter whether the atom is initially in its ground state or excited state, as time approaches to infinity, the resonance-radiation force exerted by the light on the atom approaches to zero. If the atom is initially in its ground state and excited state with the probability 1/2 respectively, and if the momentum density is a even function, then the resonance-radiation force exerted by the light on the atom is equal to zero.     

Two-Dimensional Collimation of an Atomic Beam in a Diffuse Light Field

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Improvement of Efficiency and Brightness of Red Organic Light－Emitting Devices Using Double－Quantum－Well Configuration

We present red double-quantum-well organic light-emitting devices (DQW-OLEDs), in which N,N-bis-(1-naphthyl)-N,N’-diphenyl-1,1‘-biphenyo-4,4‘-diamine (NPB) is used as potential barriers and hole transport layer, 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7, 7-thtramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) doped tris (8-hydroxyquinoline) aluminum (Alq3 ) as potential wells and emitter, undoped Alq3 as electron transport layer, respectively. The turn-on voltage is about 4 V. The maximum brightness and electroluminescent (EL) efficiency of the DQW device can reach 5916cd m^-2 at 16 V and 2.85cd A^-1 at 7 V, respectively. In addition, the EL efficiency of the DQW deviceis relatively independent of the drive voltage in the range from 5 V to 16 V.     

Bäcklund Transformation for Supersymmetric Self-Dual Theories for Semisimple Gauge Groups and a Hierarchy of Ai Solutions

We present a Bdcklund transformation (a discrete symmetry transformation) for the self-duality equations for supersymmetric gauge theories in N-extended super-Minkowski space ^4|4N for an arbitrary semisimple gauge group. For the case of anA ₁ gauge algebra we integrate the transformation starting with a given solution and iterating the process we construct a hierarchy of explicit solutions.     

Anisotropy in Thermo-Optic Coefficient of Different Polymer Systems by Attenuated Total Reflection Configuration

Thermo-optic coefficient dn/dT as well as volume expansion coefficients β of different polymer systems are measured for both TE and TM polarizations in an attenuated total reflection （ATR） configuration. Experimental results indicate that cross-linked polymer systems exhibit the thermal expansion coefficients smaller than those of the original side-chain systems. Moreover, the anisotropies in thermo-optic coefficients of the polymer systems with small birefringence exhibit linear relationship with the anisotropies in volume expansion coefficients, but the polymer systems with larger birefringence exhibit more complicated relationship.     

Performance of an Accelerometer Suspended by a Pendulum

Performances of an accelerometer suspended by a pendulum and set on ground directly are both discussed. Theoretical analysis shows that the isolation from seismic disturbances of such a suspending accelerometer is equal to that of a narrow band-pass electronic filter. This means that the effect of seismic noises to the accelerometer can be substantially suppressed by means of a pendulum suspension during its performance tests.     

Polarization Conversion of Single Photon via Scattering by a Λ System in a Semi-Infinite Waveguide

We theoretically investigate single-photon polarization conversion via scattering by an atom with Λ configuration coupled to a semi-infinite waveguide and discuss the two cases in which the Λ system is non-degenerated and degenerated. By applying the hard-wall boundary condition of the semi-infinite waveguide, it is found that singlephoton polarization conversion can be realized with unit probability for both cases under the ideal condition.Together with the polarization conversion, the frequency conversion of a single photon can also be realized with unit probability in the ideal case if the Λ system is not degenerated.     

Influence of Atomic Motion on a Microlaser in an Optical Standing—Wave Cavity

We study the microlaser in an optical standing-wave cavity injected with two-level atoms.The results have shown the obvious influence of atomic centre-of-mass motion on the microlaser,such as the photon distribution,the linewidth and the frequency shift.It was found that when the momentum of atoms is comparable to that of photons,the influence of atomic motion is dominated and the number of photons in the microlaser can be greatly enhanced,owing to part of the atomic kinetic energy being transferred to the resonator.This work provides a comparison of the related studies on the atomic motion under special assumptions.     

Experimental Investigation of the Velocity Effect on Adhesion Forces with an Atomic Force Microscope

Capillary forces are significantly dominant in adhesive forces measured with an atomic force microscope (AFM) in ambient air, which are always thought to be dependent on water film thickness, relative humidity, and the free energy of water film. We study the nature of the pull-off force on a variety of surfaces as a function of tip velocity. It is found that the capillary forces are of relatively strong dependence on tip velocity. The present experiment is expected to provide a better understanding of the work mechanism of AFM in ambient air.     

Plasticity Analysis of Nano—Grain—Sized NiAl Alloy in an Atomic Scale

The molecular dynamics method is used to simulate a uniaxial tensile deformation of 3.8 nm nano-NiAl alloy with curved amorphous-like interfaces at 0 K.Plastic deformation behaviour is studied by examining the strainstress relationship and the microstructural evolution characteristics.Atomic level analysis has shown that the micro-strain is essentially heterogeneous in simulated nano-phase samples.The plastic deformation is not only attributed to the plasticity of interfaces,but also accompanied with the plastic shear strain mechanism inside lattice distortion regions and grains.     

New Form of Legendre Polynomials Obtained by Virtue of Excited Squeezed State and IWOP Technique in Quantum Optics

Using the technique of integration within an ordered product of operators and the intermediate coordinatemomentum representation in quantum optics, as well as the excited squeezed state we derive a new form of Legendre polynomials.     

Mechanism of Formation of Carbon–Vacancy Structures in Silicon Carbide during Its Growth by Atomic Substitution

Physics of the Solid State - The mechanism of formation of carbon-vacancy structures in silicon carbide SiC from silicon vacancies that inevitably form during synthesizing SiC from Si by atomic...     

Cooperative emission from an ensemble of three-level Λ radiators in a cavity: An insight from the viewpoint of dynamics of nonlinear systems

Cooperative radiation emitted by an ensemble of three-level optical systems with a doublet in the ground state (Λ scheme), which is placed into a cyclic cavity, is studied theoretically. In contrast to the two-level model of emitters, this process with such a configuration of operating transitions may occur without population inversion in the whole, if the doublet is prepared at the initial instant in a superposition (coherent) state. In the ideal case of a Hamilton system, in which the cavity losses and relaxation in the radiator ensemble are disregarded, the conservation laws are derived, which allow a substantial reduction of the dimension of the phase space of the model (?¹¹ → ?⁵) and the application of methods of dynamics of nonlinear systems for analyzing the three-level superradiance under these conditions. The possibility of different (both quasiperiodic and chaotic) scenarios of the three-level superradiance is demonstrated on the basis of Poincaré’s mappings. Global bifurcation of the system upon a transition from the conventional superradiance regime to inversionless one is revealed. The effects of cavity losses, as well as homogeneous and inhomogeneous broadening in the system of radiators on the regularities found are also discussed.