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ABSTRACT: A scheme of atom localization based on the interference of resonance of double-dark states is proposed, in which the atom interacts with a classical standing-wave field. It is found that the localization property is significantly improved due to the interaction of double-dark resonances. It is realized that the atom is localized just at the nodes of the standing-wave field with higher precision. Moreover, an improvement by a factor of 2 in the detecting probability of a single atom within the subwavelength domain can be achieved by adjusting the probe-field detuning. This scheme shows more advantages than other schemes of atom localization.
Phys. Rev. A. 02/2006; 73(2).
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ABSTRACT: The spectral and the temporal behavior of high-intensity negatively chirped femtosecond pulses in normally dispersive media at different input parameters are experimentally studied. The spectrum of the pulse is reshaped due to strong self-actions. The pulse is self-compressed, instead of broadening, accompanied with the spectral FWHM bandwidth shortened. Steepening of the leading edge of the pulse and spectral red-shift are observed in the experiment. The numerical simulation shows that the result is in agreement with the experimental result.
Optics Express 02/2006; 14(2):979-87. · 3.59 Impact Factor
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ABSTRACT: A gain amplifier for degenerated optical parametric chirped-pulse amplification (OPCPA) with lithium triborate and cesium lithium borate (CLBO) crystals was demonstrated in a near-collinear configuration. The signal gain of the final energy amplifier with CLBO was approximately 6. After compression, the 123 fs pulse duration was obtained. Compared with potassium dihydrogen phosphate, it is confirmed that CLBO is more effective as a nonlinear crystal in a final power amplifier for terawatt or petawatt OPCPA systems. To our knowledge, this is the first demonstration of OPCPA with CLBO.
Applied Optics 02/2006; 45(3):565-8. · 1.41 Impact Factor
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ABSTRACT: A two-mode adjustable superresolving filter based on a birefringent filter is proposed. This kind of filter has superresolution in two modes of adjustment. One is rotation of the binary pupil filter on the optical axis of the system and the other is the tilt of the filter away from the pupil plane on axis parallel or perpendicular to the optical axis of the crystal. The filters act as complex amplitude filters in the former mode, and as pure phase filters in the latter. By analyzing two superresolving parameters, we obtain the optimal design parameters that ensure a large field of view, a large superresolving range, and a high setting accuracy. This kind of filter can provide more flexibility in practical applications.
Applied Optics 02/2006; 45(1):104-9. · 1.41 Impact Factor
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ABSTRACT: Surface-enhanced resonance Raman scattering (SERRS) of Rhodamine 6G (R6G) adsorbed on colloidal silver clusters in a liquid has been studied. The first observation of single molecule resonance Raman scattering in a liquid in a probed volume of 10 pL was achieved. Anisotropy of SERRS spectra of single R6G molecule and huge SERRS spectra were observed and compared with that of single molecule fixed in the dried films of sols, which revealed the intricate complex interaction between R6G molecules and the environment in a liquid.
Applied Physics Letters 01/2006; 88(3):034104-034104-3. · 3.84 Impact Factor
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ABSTRACT: Nonlinear propagation of fs laser pulses in liquids and the dynamic processes of filamentation such as self-focusing, intensity clamping, and evolution of white light production have been analyzed by using one- and two-photon fluorescence. The energy losses of laser pulses caused by multiphoton absorption and conical emission have been measured respectively by z-scan technique. Numerical simulations of fs laser propagation in water have been made to explain the evolution of white light production as well as the small-scale filaments in liquids we have observed by a nonlinear fluorescence technique.
Optics Express 01/2006; 13(25):10248-59. · 3.59 Impact Factor
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ABSTRACT: A scheme for giant enhancement of the Kerr nonlinearity in a four-level system with double dark resonances is proposed. Compared with that generated in a single-dark-resonance system, the Kerr nonlinearity can be enhanced by several orders of magnitude with vanishing linear absorption. We attribute this dramatic enhancement to the interaction of dark resonances.
Optics Letters 01/2006; 30(24):3371-3. · 3.40 Impact Factor
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ABSTRACT: The control role of the relative phase between the probe and driving fields on the gain and dispersion in an open Λ-type inversionless lasing system with spontaneously generated coherence (SGC) is investigated. It is shown that the inversionless gain and dispersion are quite sensitive to variation in the relative phase; by adjusting the value of the relative phase, electromagnetically induced transparency (EIT), a high refractive index with zero absorption and a larger inversionless gain can be realized. It is also shown that, in the contributions to the inversionless gain (absorption) and dispersion, the contribution from SGC is always much larger than that from the dynamically induced coherence for any value of the relative phase. Our analysis shows that variation in the SGC effect will cause the spectrum regions and values of the inversionless gain and dispersion to vary evidently. We also found that, under the same conditions, the values of the inversionless gain and dispersion in the open system are evidently larger than those in the corresponding closed system; EIT occurs in the open system but cannot occur in the closed system.
Journal of Modern Optics 12/2005; 52(18):2759-2769. · 1.17 Impact Factor
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ABSTRACT: It is proposed that single attosecond pulses be generated via high-order harmonic generation by using a two-color pump pulse with time dependent ellipticity. The two-color pump pulse is created by the fundamental field and its second harmonic: the fundamental field is left-circularly polarized and the second harmonic is right-circularly polarized. Numerical simulations show that single attosecond pulses can be produced in the cut-off region by using the synthesis of 20 fs left-hand and right-hand circularly polarized pulses with a pulse delay of 20 fs. The attosecond pulses produced this way are much stronger than that produced by a few-cycle linear polarized pulse of comparable intensity.
Optics Express 12/2005; 13(24):9897-902. · 3.59 Impact Factor
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ABSTRACT: Control of multiple filamentation by laser-induced microlens effect due to a nonlinear interaction of two overlapping laser beams inside a glass plate was demonstrated. Individual or multiple spots on the white light pattern which is a product of multiple filamentation through a mesh can be switched on and off with a very high contrast ratio on a femtosecond time scale. This phenomenon can find applications such as ultrafast optical switch and high-speed sampling.
Applied Physics Letters 11/2005; · 3.84 Impact Factor
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ABSTRACT: Diode-pumped passively mode-locked laser operation of Yb3+,Na+:CaF2 single crystal has been demonstrated for the first time. By using a SESAM (semiconductor saturable mirror), simultaneous transform-limited 1-ps passively mode-locked pulses, with the repetition rate of 183MHz, were obtained under the self-Q-switched envelope induced by the laser medium. The average output power of 360mW was attained at 1047nm for 3.34W of absorbed power at 976nm, and the corresponding pulse peak power arrived at 27kW, indicating the promising application of Yb3+,Na+ - codoped CaF2 crystals in achieving ultra-short pulses and high pulse peak power.
Optics Express 11/2005; 13(20):7970-5. · 3.59 Impact Factor
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ABSTRACT: The scaling law of photoionization in few-cycle laser pulses is verified in this paper. By means of numerical solution of time-dependent Schrödinger equation, the photoionization and the asymmetry degree of photoionization of atoms with different binding potential irradiated by various laser pulses are studied. We find that the effect of increasing pulse intensity is compensated by deepening the atomic binding potential. In order to keep the asymmetric photoionization unchanged, if the central frequency of the pulse is enlarged by k times, the atomic binding potential should also be enlarged by k times, and the laser intensity should be enlarged by k(3) times.
Optics Express 11/2005; 13(22):8708-16. · 3.59 Impact Factor
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ABSTRACT: By employing pump-probe back longitudinal diffractometry, the electron density and decay dynamics of a weak plasma channel created by a 1-KHz fs laser in air has been investigated. With ultrashort laser pulses of 50 fs and low energy of 0.6 mJ, we observe weak plasma channels with a length approximately 2 cm in air. An analytical reconstruction method of electron density has been analyzed, which is sensitive to the phase shift and channel size. The electron density in the weak plasma channel is extracted to be about 4 x 10(16) cm(-3). The diameters of the plasma channel and the filament are about 50 and 150 microm, respectively, and the measurable electron density can be extended to less than 10(15) cm(-3). Moreover, a different time-frequency technique called linearly chirped longitudinal diffractometry is proposed to time-resolved investigate ultrafast ionization dynamics of laser-irradiated gas, laser interaction with cluster beam, etc.
Physical Review E 09/2005; 72(2 Pt 2):026412. · 2.26 Impact Factor
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ABSTRACT: Several schemes for coherent quantum control of atomic and molecular processes have been pro-posed and investigated by using the techniques of adiabatic passage and ultrashort pulses, respec-tively. Some interesting results have been found.
Journal- Korean Physical Society 07/2005; 4680. · 0.45 Impact Factor
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ABSTRACT: High power optical parametric chirped pulse amplifiers at 1064 nm and 780 nm were demonstrated using LBO crystals pumped by synchronized frequency-doubled Nd:glass laser and Ti:sapphire laser. Some of their applications are presented and discussed.
Lasers and Electro-Optics, 2005. (CLEO). Conference on; 06/2005
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ABSTRACT: We investigate experimentally the self-compression behavior of high-power femtosecond pulses in normally dispersive solid bulk media with un-chirped laser pulses and negatively chirped laser pulses. It is demonstrated that high-power femtosecond laser pulses can be compressed by the nonlinear propagation in the transparent bulk media, and the temporal and spectral characteristics of resulted pulses were found to be significantly affected by the input laser intensity, with higher intensity corresponding to shorter compressed pulses. By the propagation in a piece of thin BK7 glass plate, a self-compression from 50fs to 20fs was achieved, with a compression factor of about 2.5. However, the output laser pulse was observed to be split into two peaks when the input laser intensity is high enough to generate supercontinuum and conical emission. When the input laser pulse is negatively chirped, the spectra of the pulse is reshaped and narrowed due to strong self-action effects, and the temporal pulse duration is found to be self-compressed, instead of broadening. With the increase in the input pulse intensity, the resulted self-compressed pulses became even shorter than the input laser pulse, and also shorter than sech2 transform-limited pulse according to the corresponding spectra. The self-compression scheme is simple and robust, and it is promising as a new pulse compression method to achieve intense laser pulses of few cycles.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
04/2005;
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ABSTRACT: Attosecond-pulse extreme-ultraviolet (XUV) photoionization in a two-color laser field is investigated. Attosecond pulse trains with different numbers of pulses are examined, and their strong dependence on photoelectronic spectra is found. Single-color driving-laser-field-assisted attosecond XUV photoionization cannot determine the number of attosecond pulses from the photoelectronic energy spectrum that are detected orthogonally to the beam direction and the electric field vector of the linearly polarized laser field. A two-color-field-assisted XUV photoionization scheme is proposed for directly determining the number of attosecond pulses from a spectrum detected orthogonally.
Optics Letters 04/2005; 30(5):564-6. · 3.40 Impact Factor
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Quantum Electronics Conference, 2005. International; 02/2005
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ABSTRACT: Coherent anti-Stokes Raman scattering (CARS) microscopy with the combining of confocal and CARS techniques is a remarkable alternative for imaging chemical or biological specimens that neither fluoresce nor tolerate labeling. The CARS is a nonlinear optical process, the imaging properties of CARS microscopy will be very different from the conventional confocal microscopy. In this paper, we calculated the propagation of CARS signals by using the wave equation in medium and the slowly varying envelope approximation (SVEA), and find that the intensity angular distributions vary considerably with the different experimental configurations and the different specimen shapes. So the conventional description of microscopy (e.g., the point spread function) will fail to descript the imaging properties of CARS microscopy.
Aspects. 01/2005; 257258:525-534.
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ABSTRACT: We analyse a four-wave mixing (FWM) scheme in a five-level atomic system in which double-dark resonances are present. It is found that the enhancement of FWM in both electromagnetically induced transparency (EIT) windows can be obtained even without the condition of multiphoton resonance. Moreover, the conversion efficiency of FWM in one EIT window can be much larger than that in the other due to the presence of interacting dark resonances.
J. Phys. B: At. Mol. Opt. Phys. 01/2005; 38:2657-2663.
