Phase modulation of propagation effect with Doppler broadening

This paper studies the propagation effect in a closed lambda-type three-level atomic system with Doppler broadening. It is shown that, Doppler broadening due to atomic motion and propagation effect associated with driving field depletion along the active medium decreases obviously the gain and output of the lasing without inversion （LWI）; the relative phase between the probe and driving fields has a remarkable modulation role to the propagation effect on LWI when Doppler broadening presents; by choosing suitable value of the relative phase, we can get the largest gain and output of LWI.     

Nonlinear dynamics study of an open resonant A-type system

A way resulting in lasing without inversion (LWI) in an open resonant A-type system from a nonlinear dynamics viewpoint is investigated. The destabilization of the non-lasing solution can occur not only through pitchfork bifurcation, giving rise to continuous wave LWI, but also through Hopf bifurcation,giving rise to self-pulsing LWI. This is much different from that of the corresponding closed resonant A-type system in which the destabilization of the non-lasing solution can occur only through pitchfork bifurcation. The effects of the unsaturated gain coefficient, cavity loss coefficient, atomic injection and exit rates on the two bifurcations are discussed.     

Effect of spontaneously generated coherence on inversionless lasing gain in an atomic system with Doppler broadening

We have studied the effect of the spontaneously generated coherence (SGC) on gain of lasing without inversion (LWI) in a closed three-level $\Lambda $-type atomic system with Doppler broadening. It is shown that, regardless of the driving and probe fields being co- or counter-propagating, at a suitable value of the Doppler width, we can obtain a much larger LWI gain with SGC than that without SGC; and the region of the LWI gain spectrum with SGC is obviously larger than that without SGC. When the Doppler width takes a constant value, the gain does not monotonically decrease or increase with increasing strength of SGC, the largest LWI gain can be obtained by adjusting strength of SGC. Generally speaking, the co-propagating probe and driving fields is favourable to obtain a larger LWI gain.     

Bi-photonic transient gratings in bulk azo-dye containing poly (methyl methacrylate) matrix

Integrated optical micro-devices require the developmentof the holographic technique for the realization of lensmatrices, prisms, and diffraction gratings of micrometricdimensions. Both permanent and transient holographicsystems find important applications in this field. Mate-rials containing photo-responsive dyes have been foundto be suitable for such a task and therefore become at-tractive in the field of optical communication and high-density optical data storage[1-4]. Azo-dye containingpol…     

Effect of vacuum-induced coherence on lasing without inversion in an equispaced three-level ladder system

The effects of vacuum-induced coherence (VIC) on the properties of the absorption and gain of the probe field in an equispaced three-level ladder atomic system are investigated. It is found that lasing without inversion (LWI) is remarkably enhanced due to the effect of VIC in the case of the small incoherent pump rate.     

Laser controlling chaotic region of a two-component Bose-Einstein condensate

Because of the experimental realization of Bose-Einstein condensation in weakly interacting atomic systems, many fundamental works for Bose-Einstein condensates (BECs) have been carried out. One of the most interest- ing future prospects for the BECs is their application as a source of coherent matter waves[1-4] in atomic optics and atomic interferometry. Meanwhile, the analogies between coherent matter waves and coherent photons have been discussed as an "atom laser" [5-9]. Particularly, …     

Theoretical study of aging effects on LaNi_5 tritium storage

1 Introduction LaNi5 intermetallic compounds, used in storage, separation and purification of hydro- gen and hydrogen isotopes, are known for a high-density storage, easy activation, low pressure, and rapid and reversible absorption and desorption[1-15]. Tritium as an impor- tant material in the nuclear industry is radioactively decaying into 3He with a half-life of 12.3 years. With time, there are many changes in the electronic and physical properties of the tritide for the deposition of 3He…     

Searching for high-frequency gravitational waves with a ground high alternating magnetic field

正Recently,with the precise laser interferometers the LIGOVirgo collaboration[1-4]has realized the direct detection of the GWs,by probing their minute mechanical displacements.The peak strains of the detected GWs are at the order of 10-21and their frequencies are in the low-and intermediate frequency band,i.e.,dozens and hundreds of Hertz.Given the GWs could exist at any frequency[5,6],in principle,probing the GWs in the wider bands[7,8],typically the high frequency GWs expected by a series of models for cosmology     

Quantum nonlocality can be distributed via separable states

正Quantum nonlocality is one of the most astonishing features in quantum physics.It is of great importance in understanding the conceptual foundations of quantum theory and is closely related to certain quantum information processing such as quantum protocols for decreasing communication complexity[1]and secure quantum communication[2,3],see refs.[4-9]for more details.     

EXAFS Study on Structure of Sulfided K—Co—Mo Catalysts

Mixed alcohol is of great promise as octane improver in automotive fuel,and hopeful to replace the MTBE to reduce the environmental pollution,In this field,alkali-promted molybdenum-based catalysts have been given special interest because of their excellent sulfur-tolerance for synthesis of mixed alcohol from CO H2,It was reported that the coblat is a favorable promoter for enhancing alcohol production,especially for improving the selectivity for C2 alcohol[1-3],moreover,strong interaction between Con and Mo is in favor of mixed alcohol synthesis[4].Recently,we prpared a kind of K-Co-Mo ultrafine particles by sol-gel method and it shows much smaller particle size but higher activty and selectivity toward alcohol formation than the one prepared by conventional method[5],The aim of the present work is to research the micostructures of the Mo and Co species in the K-Co-Mo samples prepared by different method.     

Quantum coherence of multiqubit states in correlated noisy channels

Quantum coherence captures the essential nature of a quantum system[1]and can serve as a resource for quantum information processing[2].Recent studies also provide evidence that long-lived quantum coherence is crucial for overcoming the classical limits of measurement accuracy in quantum metrology[3-5].However,in practice,the unavoidable interaction of a principal system with its surroundings results in decoherence in most situations.Consequently,the advantage of quantum coherence in empowering the performance of quantum tasks will disappear in a very short time interval,which remains one of the major obstacles in its potential application.     

Hyperpolarizabilities of alkaline-earth metal ions Be+, Mg+, and Ca+

The knowledge of the hyperpolarizabilities of atoms and ions is helpful for the analysis of the high order effects of the frequency shifts in precision spectroscopy experiments. Liu et al. [Phys. Rev. Lett. 114, 223001(2015)] proposed to establish all-optical trapped ion clocks using laser at the magic wavelength for clock transition. To evaluate the high-order frequency shifts in this new scheme of optical clocks, hyperpolarizabilities are needed, but absent. Using the finite field method based on the B-spline basis set and model potentials, we calculated the electric-field-dependent energy shifts of the ground and low-lying excited states in Be+, Mg+, and Ca+ in the field strength range of 0.0-6×10.5 a.u.. The scalar and tensor polarizabilities(α0, α2) and hyperpolarizabilities(γ0, γ2, γ4) were deduced. The results of the hyperpolarizabilities for Be+ showed good agreement with the values in literature, implying that the present method can be applied for the effective estimation of the atomic hyperpolarizabilities,which are rarely reported but needed in experiments. The feasibility of optical trapping of Ca+ is discussed, and the contributions of hyperpolarizabilities to the transition frequency shift for Ca+ in the optical dipole trap are estimated using quasi-electrostatic approximation.     

The optimal path of piston motion for Otto cycle with linear phenomenological heat transfer law

An Otto cycle engine with internal and external irreversibilities of friction and heat leakage, in which the heat transfer between the working fluid and the environment obeys linear phenomenological heat transfer law [q ∝△(T -1)], is studied in this paper. The optimal piston motion trajectory for maximizing the work output per cycle is derived for the fixed total cycle time and fuel consumed per cycle. Optimal control theory is applied to determine the optimal piston trajectories for the cases of with and w...     

Suppression of bend loss in writing of three-dimensional optical waveguides with femtosecond laser pulses

正Optical waveguides are one of the fundamental building blocks for integrated photonic applications[1-6].Recently,femtosecond laser has been used for inscribing optical waveguides in various transparent materials such as glass,crystals and polymers thanks to the unique capability of the locally modifying refractive index in the vicinity of the focal spot[7-11].This has allowed producing three-dimensional photonic circuits for a broad spectrum of applications ranging from quantum information processing and miniaturized     

THz spectrum of reduced glutathione

The collective rotational and vibrational transitions of most of large bio-molecules distribute in about 0.1-10 THz range, and the response to THz wave mainly results from the collective vibration modes determined by configuration and conformation of large molecules[1,2]. In 2000, A. G. Markelz et al. first used THz-TDS for studying the characteristic of DNA, bovine serum and collagen in the THz band[3], found these three molecules have characteristic absorption and obtained some useful …     

The generalized quasi-variational principles of non-conservative systems with two kinds of variables

Many investigators have paid much attention to the generalized variational principles in mechanics of deformable bodies. Ref. [1] laid a foundation for the generalized varia-tional principles by studying the principle of complementary energy, from both theoreti-cal and practical points of view. Ref. [2] established the generalized variational princi-ples of elasticity and plasticity and provided the theoretical foundation for the mixed finite element method, which was widely used in the field.…     

Molecular dynamics simulation on generalized stacking fault energies of FCC metals under preloading stress

Molecular dynamics(MD) simulations are performed to investigate the effects of stress on generalized stacking fault(GSF) energy of three fcc metals(Cu, Al, and Ni). The simulation model is deformed by uniaxial tension or compression in each of [111], [11-2], and [1-10] directions, respectively, before shifting the lattice to calculate the GSF curve. Simulation results show that the values of unstable stacking fault energy(γusf), stable stacking fault energy(γsf), and unstable twin fault energy(γutf) of the three elements can change with the preloaded tensile or compressive stress in different directions.The ratio of γsf/γusf, which is related to the energy barrier for full dislocation nucleation, and the ratio of γutf/γusf, which is related to the energy barrier for twinning formation are plotted each as a function of the preloading stress. The results of this study reveal that the stress state can change the energy barrier of defect nucleation in the crystal lattice, and thereby can play an important role in the deformation mechanism of nanocrystalline material.     

First-principles study of structural,electronic,elastic,and thermal properties of Imm2-BC

Using the first-principles method, we predict an orthorhombic boron–carbon binary structure with sp~ace group Imm2.This structure is verified to be dynamically and mechanically stable, and possesses a cavity of 27.5 ~2 that makes it a potential molecular sieve material. The C sp~2 and sp~3 hybridized bonding in Imm2 BC is an important factor for its structural stability. The energy band calculations reveal that Imm2 BC is a semiconductor with a band gap of 1.3 eV and has a promising application in the electro-optic field. The lattice thermal conductivity along the crystal [100] direction at room temperature is 186 W·m~(-1)·K~(-1), that is about 5 times higher than those along the [010] and [001] directions, which stems from the different group velocity along the crystal direction. Moreover, the acoustic-optical coupling is important for heat transp~ort in Imm2 BC, and the contribution of optical phonons to lattice thermal conductivity in the [100], [010], and [001]directions is 49%, 59%, and 61%, resp~ectively. This study gives a fundamental understanding of the structural, electronic,elastic, and heat transp~ort properties in Imm2 BC, further enriching the family of boron–carbon binary compounds.     

Singularity-free approximate analytical solution of capillary rise dynamics

正Capillary rise is one of the most well-known and vivid illustrations of capillarity(shown in Figure 1).Knowledge of capillarity laws is important in oil recovery,civil engineering,dyeing of textile fabrics,ink printing,and a variety of other fields.It is capillarity that brings water to the upper layer of soils,drives sap in plants,or lays the basis for the operation of pens[1-10].Washburn[1]developed an equation to describe the rate     

Development of a polarized ~3He neutron spin filter based on spin exchange optical pumping at China Mianyang Research Reactor

正Spin-polarized~3 He gas is widely used in many research areas.It is used to search for new spin-dependent interactions beyond the standard model[1,2].It works as a target for electron scattering when studying the spin structure of neurons in high-energy and nLuclear physics[3].Also,it works as a neutron spin filter(NSF)for polarizing/analyzing neutron polarizations in scattering experiments[4-7].One of the ad-