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排序方式: 共有805条查询结果,搜索用时 359 毫秒
81.
对聚焦光束通过有一定外加电场BaTiO3晶体时的自陷现象进行了理论分析,发现在正切割晶体中观察空间孤子是不合适的,因仅利用了很微小的电光系数γ33。对异型切割情况进行了讨论,给出了维持光束自陷的外加电场范围和实际观察的最佳角度。 相似文献
82.
83.
Novel effects resulting from joint action of chirality and non-linearity are discussed using a basic equation describing the
temporal evolution of fields in a chiral medium with Kerr non-linearity. The spatial chirality effect is characterized through
the Born-Fedorov formalism. Our simulations are based on the split-step Fourier method and the solution of the Stokes parameters.
The numerical results show the chiral effect on solitons with circular polarization and mixed polarization spatial solitons. 相似文献
84.
85.
The flow of a viscous liquid film down a vertical cylinder in the gravity field is considered. In the case of small Reynolds numbers for long-wave perturbations on a cylinder of radius much greater than the film thickness, the problem can be reduced to a single nonlinear equation for the evolution of the film thickness perturbation. For axially symmetric solutions, this equation coincides with the well-known Sivashinsky-Kuramoto equation. The results of a numerical analysis of this equation for three-dimensional stationary traveling solutions of the problem are reported. The effect of the problem parameters on the solution behavior is demonstrated. Soliton type solutions are presented. 相似文献
86.
L. M. Kovachev L. I. Pavlov L. M. Ivanov D. Y. Dakova 《Journal of Russian Laser Research》2006,27(3):185-203
We have investigated the evolution of picosecond and femtosecond optical pulses governed by the amplitude vector equation
in the optical and UV domains. We have written this equation in different coordinate frames, namely, in the laboratory frame,
the Galilean frame, and the moving-in-time frame and have normalized it for the cases of different and equal transverse and
longitudinal sizes of optical pulses or modulated optical waves. For optical pulses with a small transverse size and a large
longitudinal size (optical filaments), we obtain the well-known paraxial approximation in all the coordinate frames, while
for optical pulses with relatively equal transverse and longitudinal sizes (so-called light bullets), we obtain new non-paraxial
nonlinear amplitude equations. In the case of optical fields with low intensity, we have reduced the nonlinear amplitude vector
equations governing the light-bullet evolution to the linear amplitude equations. We have solved the linear equations using
the method of Fourier transform. An unexpected new result is the relative stability of light bullets and the significant decrease
in the diffraction enlargement of light bullets with respect to the case of long pulses in the linear propagation regime. 相似文献
87.
G. Tonini F. Werner Y. Castin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(2):283-294
We investigate theoretically the formation of a vortex lattice in
a superfluid two-spin component Fermi gas in a rotating harmonic trap, in a BCS-type
regime of condensed non-bosonic pairs.
Our analytical solution of the superfluid
hydrodynamic equations, both for the 2D BCS equation of state
and for the 3D unitary quantum gas, predicts that the vortex free gas is
subject to a dynamic instability for fast enough rotation.
With a numerical solution of the full
time dependent BCS equations in a 2D model, we confirm the existence of this dynamic
instability and we show that it leads to the formation of a regular pattern
of quantum vortices in the gas. 相似文献
88.
K. P. Schmidt A. Reischl G. S. Uhrig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(2):343-352
In this work we give a consistent picture of the thermodynamic properties of
bosons in the Mott insulating phase when loaded adiabatically into
one-dimensional optical lattices. We find a crucial dependence of the
temperature in the optical lattice on the doping level of the Mott
insulator. In the undoped case, the temperature is of the order of the large
onsite
Hubbard interaction. In contrast, at a finite doping level the
temperature jumps almost immediately to the order of the small hopping
parameter. These two situations are investigated on the one hand by considering
limiting cases like the atomic limit and the case of free fermions. On the
other hand, they are examined using a quasi-particle conserving continuous
unitary transformation extended by an approximate thermodynamics for
hardcore particles. 相似文献
89.
E. Lundh 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):517-520
Two effects are identified that affect the visibility of the
Mott transition in an atomic gas in an optical lattice confined
in a power-law potential. The transition can be made more
pronounced by increasing the power law, but at the same time,
experimental uncertainty in the number of particles will
induce corresponding fluctuations in the measured condensate
fraction. Calculations in two dimensions
indicate that a potential slightly more flat-bottomed than a
quadratic one is to be preferred for a wide range of
particle number fluctuation size. 相似文献
90.
双芯耦合光纤中高阶色散对光孤子相互作用的影响 总被引:3,自引:0,他引:3
利用变分原理对耦合纤芯中传输光孤子之间的相互作用和形成束缚孤子态的条件进行了研究,发现高阶色散减弱甚至可以消除光孤子之间的相互作用。这一结果为耦合光纤器件的设计提供了一种实用消除光孤子之间相互作用的方法。 相似文献