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Zhang D.,Wuhan Polytechnic University | Yu R.,Wuhan Institute of Technology | Li J.,Huazhong University of Science and Technology | Li J.,Key Laboratory of Fundamental Physical Quantities Measurement of Ministry of Education | And 2 more authors.
Optics Communications | Year: 2014

A scheme of two-dimensional atom localization is proposed based on the phase-sensitive probe absorption and gain in a four-level atomic system with a closed-loop configuration. Due to the spatially dependent atom-field interaction, the position probability distribution of the atom can be directly determined by measuring the resulting absorption and gain spectra of the weak probe laser field. It is found that the phase-sensitive property of the atomic system significantly improves the localization behavior. Especially the maximal probability of finding the atom at a particular position within the sub-wavelength domain of the standing waves can arrive at unity by appropriate choice of the system parameters. © 2014 Elsevier B.V.


He L.,Huazhong University of Science and Technology | Li Y.,Huazhong University of Science and Technology | Zhang Q.,Huazhong University of Science and Technology | Lu P.,Huazhong University of Science and Technology | Lu P.,Key Laboratory of Fundamental Physical Quantities Measurement of Ministry of Education
Optics Express | Year: 2013

We propose an efficient method to generate an ultra-broadband supercontinuum by using a three-color field synthesized by a 1600 nm driving pulse and two weak (3200 nm and 400 nm) control pulses. The results show that the acceleration and ionization steps in the HHG process are simultaneously controlled in our scheme, which can not only broaden the bandwidth but also enhance the harmonic yields of the generated spectrum. Thus a high-efficiency supercontinuum with the photon energies ranging from 205 eV to 480 eV is observed. Based on our 3D propagation simulations, we show that the short quantum path of the supercontinuum is well phase-matched and can be selected under suitable propagation conditions. Thereby, the modulation due to quantum path interference is largely reduced and intense isolated sub-100 as pulses with tunable central wavelengths are directly obtained within water window spectral region. © 2013 Optical Society of America.


Li Y.,Huazhong University of Science and Technology | Zhu X.,Huazhong University of Science and Technology | Zhang Q.,Huazhong University of Science and Technology | Qin M.,Huazhong University of Science and Technology | And 2 more authors.
Optics Express | Year: 2013

We perform a quantum-orbit analysis for the dependence of high-order-harmonic yield on the driving field ellipticity and the polarization properties of the generated high harmonics. The electron trajectories responsible for the emission of particular harmonics are identified. It is found that, in elliptically polarized driving field, the electrons have ellipticity-dependent initial velocities, which lead to the decrease of the ionization rate. Thus the harmonic yield steeply decreases with laser ellipticity. Besides, we show that the polarization properties of the harmonics are related to the complex momenta of the electron. The physical origin of the harmonic ellipticity is interpreted as the consequence of quantum-mechanical uncertainty of the electron momentum. Our results are verified with the experimental results as well as the numerical solutions of the time dependent Schrödinger equation from the literature. © 2013 Optical Society of America.


Liu S.,Huazhong University of Science and Technology | Liu S.,Hubei University of Arts and Science | Li J.,Huazhong University of Science and Technology | Li J.,Key Laboratory of Fundamental Physical Quantities Measurement of Ministry of Education | And 2 more authors.
Optics Express | Year: 2013

We investigate the entanglement generation between two nitrogen-vacancy (NV) centers in diamond nanocrystal coupled to a high-Q counterpropagating twin whispering-gallery modes (WGMs) of a microtoroidal resonator. For looking into the degree and dynamics of the entanglement, we calculate the concurrence using the microscopic master equation approach. The influences of the coupling strength between the WGMs (or the size of the two spherical NV centers), the distance between two NV centers, the frequency detuning between the NV center and microresonator, and the initial state of the system on the dynamics of concurrence are discussed in detail. It is found that the maximum entanglement between the two NV centers can be created by properly adjusting these controllable system parameters. Our results may provide further insight into future solid-state cavity quantum electrodynamics (CQED) system for quantum information engineering. © 2013 Optical Society of America.


Zhou Y.,Huazhong University of Science and Technology | Huang C.,Huazhong University of Science and Technology | Liao Q.,Huazhong University of Science and Technology | Lu P.,Huazhong University of Science and Technology | Lu P.,Key Laboratory of Fundamental Physical Quantities Measurement of Ministry of Education
Physical Review Letters | Year: 2012

With a classical ensemble model that includes electron correlations during the whole ionization process, we investigate strong-field sequential double ionization of Ar by elliptically polarized pulses at the quantitative level. The experimentally observed intensity-dependent three-band or four-band structures in the ion momentum distributions are well reproduced with this classical model. More importantly, the experimentally measured ionization time of the second electrons by A.N. Pfeiffer et al., which cannot be predicted by the standard independent-electron model, is quantitatively reproduced by this fully classical correlated model. The success of our work encourages classical descriptions and interpretations of the complex multielectron effects in strong-field ionization where nonperturbative quantum approaches are currently not feasible. © 2012 American Physical Society.

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