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Projectile angular-differential cross sections for single electron transfer in fast He^+-He collisions

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Chinese physics B 2015年第3期24卷 127-135页

作者： Ebrahim Ghanbari-Adivi Hoda Ghavaminia department of physics and Isfahan Quantum optics Group (IQOG) Faculty of ScienceUniversity of Isfahan

The four-body Coulomb–Born distorted wave approximation is applied to investigate the integral as well as projectile angular-differential cross sections for single-electron capture in the collision of energetic singly positive charged helium ions with helium atoms in their ground states. The formalism satisfies the correct boundary conditions. The influence of the dynamic electron correlations on the cross sections is studied by considering the inter electronic interactions in the complete perturbation potentials in post form. Also, the sensitivity of the cross sections to the static electronic correlations is studied by using the single-zeta and the highly correlated Byron–Joachain wave functions to describe the initial bound state of the active electrons. The obtained results for the energy range of 40–5000 ke V/amu are reported and compared with other three- and four-body theoretical data and available experimental measurements. The comparison leads us to discuss the validity of the applied approach and survey the interaction effects on the cross sections by recognizing the electron–electron interaction. Particularly, for differential cross sections, the comparison of the present four-body method with the experiment shows that the agreement is not as good as that for its three-body version.

关键词： Coulomb–Born distorted-wave approximation four-body approximation Coulomb boundary conditions differential and total cross secti

Laser frequency stabilization and shifting by using modulation transfer spectroscopy

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Chinese physics B 2014年第10期23卷 242-247页

作者：程冰王兆英吴彬许翱鹏王启宇徐云飞林强 Institute of optics Department of Physics Zhejiang University

The stabilizing and shifting of laser frequency are very important for the interaction between the laser and atoms. The modulation transfer spectroscopy for the 87Rb atom with D2 line transition F = 2 →F＇ = 3 is used for stabilizing and shifting the frequency of the external cavity grating feedback diode laser. The resonant phase modulator with electro-optical effect is used to generate frequency sideband to lock the laser frequency. In the locking scheme, circularly polarized pump- and probe-beams are used. By optimizing the temperature of the vapor, the pump- and probe-beam intensity, the laser linewidth of 280 kHz is obtained. Furthermore, the magnetic field generated by a solenoid is added into the system. Therefore the system can achieve the frequency locking at any point in a range of hundreds of megahertz frequency shifting with very low power loss.

关键词： laser stabilization spectroscopy diode lasers line shapes and shifts

Exact Evolution of Ultrashort Hollow-Airy Pulses in the Spatiotemporal Domain

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Chinese physics Letters 2015年第1期32卷 47-51页

作者：张敬芳王兆英林强 Institute of optics Department of PhysicsZhejiang University

An exact analytic expression for an ultrashort hollow-Airy wave packet is presented beyond the slowly varying envelope approximation. The hollow-Airy wave packet combines the hollow-Gaussian beam in the spatial domain and the Airy pulse in the temporal domain. The spatiotemporal propagation dynamics of the ultrashort hollow- Airy pulse are analyzed by the numerical simulations. During the propagation in free space, the spatial intensity profile evolves from hollow-Gaussian to Gaussian shape; the temporal intensity profile retains Airy shape over several Rayleigh ranges. The acceleration property of the ultrashort Airy pulse is also demonstrated.

关键词： Exact Evolution of Ultrashort Hollow-Airy Pulses in the Spatiotemporal Domain cycle

High contrast atomic magnetometer based on coherent population trapping

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Chinese physics B 2014年第2期23卷 477-480页

作者：杨爱林杨国卿徐云飞林强 Institute of optics Department of PhysicsZhejiang University

We present an experimental and theoretical investigation of the coherent population trapping （CPT） resonance excited on the D1 line of 87Rb atoms by bichromatic linearly polarized laser light. The experimental results show that a lin｜｜lin tran- sition scheme is a promising alternative to the conventional circular-circular transition scheme for an atomic magnetometer. Compared with the circular light transition scheme, linear light accounts for high-contrast transmission resonances, which makes this excitation scheme promising for high-sensitivity magnetometers. We also use linear light and circular light to detect changes of a standard magnetic field, separately.

关键词： high contrast atomic magnetometer coherent population trapping

A laser pump-re-pump atomic magnetometer

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Chinese physics B 2013年第12期22卷 177-181页

作者：杨爱林杨国卿蔡勋明徐云飞林强 Institute of optics Department of Physics Zhejiang University

We demonstrate experimentally an atomic magnetometer based on optical pumping theory, a magnetic resonance that is induced by a radio frequency field and dependent on the magnetic field strength. Compared with the conventional method using one radiation field, which is used not only as the probe beam but also as a pump beam, the additional re-pump beam can increase remarkably the amplitude of the signal. It is shown that the amplitude of the magnetic field resonance signal can increase more than 55% by using an additional re-pump beam, which makes the sensitivity of the magnetometer higher. Finally, we investigate the relation between amplitude of the signal and re-pump laser power, and calculate the atomic population in the trapping states with rate equations.

关键词： atomic magnetometer optical pumping sensitivity

Generation of four-atom Greenberger-Horn-Zeilinger state via adiabatic passage

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Chinese physics B 2013年第5期22卷 141-146页

作者：张春玲陈美锋 Laboratory of Quantum optics Department of PhysicsFuzhou University

We propose a scheme to generate a Greenberger-Horn-Zeilinger （GHZ） state of four atoms trapped in a two-mode optical cavity via an adiabatic passage. The scheme is robust against moderate fluctuations of the experimental parameters. Numerical calculations show that the excited probabilities of both the cavity modes and the atoms are tiny and depend on the pulse peaks of the classical laser fields. For certain decoherence due to the atomic spontaneous emission and the cavity decay, there exits a range of pulse peaks to get a high fidelity.

关键词： Greenberger-Horn-Zeilinger (GHZ) state adiabatic passage cavity quantum electrodynamics

Electron correlation in fast ion-impact single ionization of helium atoms

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Chinese physics B 2015年第1期24卷 240-246页

作者： E.Ghanbari-Adivi S.Eskandari department of physics and Isfahan Quantum optics Group (IQOG) Faculty of Science University of Isfahan Isfahan 81746-73441 Iran

A four-body distorted-wave approximation is applied for theoretical analysis of the fully differential cross sections（FDCS） for proton-impact single ionization of helium atoms in their ground states. The nine-dimensional integrals for the partial amplitudes are analytically reduced to closed-form expressions or some one-dimensional integrals which can be easily calculated numerically. Calculations are performed in the scattering and perpendicular planes. The influence of the target static electron correlations on the process is investigated using a number of different bound-state wave functions for the ground state of the helium targets. An illustrative computation is performed for 75-ke V proton–helium collisions and the obtained results are compared with experimental data and other theoretical predictions. Although for small momentum transfers, the comparison shows a reasonable agreement with experiments in the scattering and perpendicular planes, some significant discrepancies are still present at large momentum transfers in these planes. However, our results are compatible and for some cases, better than those of the other sophisticated calculations.

关键词： single ionization four-body collision distorted-wave approximation electron correlation

Programmable complex pumping field induced color-on-demand random lasing in fiber-integrated microbelts for speckle free imaging

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Science China(Information Sciences) 2023年第12期66卷 251-260页

作者： Xiaoyu SHI Kaiyue SHEN Yaoxing BIAN Wanting SONG Jun RUAN Zhaona WANG Tianrui ZHAI College of physics and Optoelectronics Faculty of ScienceBeijing University of Technology Applied optics Beijing Area Major Laboratory Department of PhysicsBeijing Normal University

Miniaturized lasers with on-demand color emission have immense potential in the development of integrated imaging sources. Random lasers(RLs) with cavity-free structures and low spatial coherence are promising candidates for multicolor imaging sources. However, the wide tuning range and high tuning accuracy of continuous and reversible random lasing color with a defined emissive direction remain challenging. Here, random lasing with on-demand color emission and defined emissive direction is realized in fiber-integrated microbelts through programmable pumping. Individual RL microbelts as RL units doped with blue(B)-, green(G)-, and red(R)-emissive dyes and titanium dioxide nanoparticles are assembled on an optical fiber, resulting in high-performance B/G/R lasing. The optical fiber functions as a waveguide that guides the multicolor RL to ensure a defined directional emission. By manipulating the combination of the B/G/R RL units on the waveguide, distinctive lasing colors covering the entire visible spectrum are obtained, including white-colored random lasing. To realize dynamically controllable lasing for on-demand color emission, a pumping strategy with programmable excitation is proposed by shaping the pump beams into different beam arrays for precisely pumping the RL unit combination. We envision that fiber-integrated RL sources can be implemented in various imaging applications, such as biomedical diagnosis, multiplexed communication, and optical sensing.

关键词： random laser multi-color pump control fiber-integrated directional emission

Dissipative dynamics of an entangled three-qubit system via non-Hermitian Hamiltonian: Its correspondence with Markovian and non-Markovian regimes

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Chinese physics B 2021年第3期30卷 283-292页

作者： M Rastegarzadeh M K Tavassoly Laser and optics Group Faculty of PhysicsYazd UniversityYazd 89195-741Iran

We investigate an entangled three-qubit system in which only one of the qubits experiences the decoherence effect by considering a non-Hermitian Hamiltonian,while the other two qubits are isolated,i.e.,do not interact with environment,***,the time evolution of the density matrix(for the pure as well as mixed initial density matrix)and the corresponding reduced density matrices are obtained,by which we are able to utilize the dissipative non-Hermitian Hamiltonian model with Markovian and non-Markovian regimes via adjusting the strange of the non-Hermitian term of the total Hamiltonian of the under-considered system.

关键词： non-Hermitian Hamiltonian entanglement concurrence measure Markovian and non-Markovian regimes