共查询到8条相似文献,搜索用时 0 毫秒
1.
A. A. Zemlyanov Y. E. Geints 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):349-357
The generic scenario of intense femtosecond laser pulse propagation in the
air from the viewpoint of evolution of its integral effective parameters
(energy transfer coefficient, effective radius, effective duration, limiting
angular divergence) is considered. The analysis of variation of the
effective parameters along the propagation path in the single and multiply
filamentation scenarios based on numerical calculations is presented. It is
shown that the process of self-action of the ultrashort radiation is
characterized by the formation in a medium of the nonlinearity layer, after
which optical pulse propagates quasi-linearly with the limiting angular
divergence that depends mainly on initial pulse power. The effective pulse
temporal duration and the effective beam radius increase after the passage
through the nonlinearity layer, and their values are mostly determined by
the initial beam power also. The coefficient of energy transmission of
femtosecond laser radiation is lower than in the linear medium and has a
tendency to decrease with the increase of the pulse power. 相似文献
2.
D. Benredjem V. Bommier H. Guennou C. Möller A. Sureau 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(1):83-87
In order to solve the radiative-transfer equation for polarized beams propagating in plasmas a matrix approach is applied.
The solution is the four-components Stokes vector, and the effect of the medium on the state of the radiation is represented
by an amplification operator. Our approach is applied to the neon-like germanium 23.6 nm line, when a right-circularly polarized
beam is injected into an amplifying plasma. The conditions governing the recovery of the initial polarization state are investigated
over the entire spectrum of the output.
Received: 10 October 1997 / Revised: 12 January 1998 / Accepted: 27 January 1998 相似文献
3.
L.-M. Zhao B.-Y. Gu 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(2):275-280
We apply the expanded basis method (EBM) to investigate
the behavior of light in a two-dimensional photonic crystal (PC) slab. This
method is based on expanded completeness bases, including both
the propagation and evanescence modes.
We calculate the reflected and transmitted coefficients and
the corresponding field distributions in the case of
multiple mode transportation.
We also show the related phases which exhibit oscillations
with the frequency of the incident light. 相似文献
4.
Experiments by Gittings, Bandyopadhyay and Durian (Europhys. Lett. 65, 414 (2004)) demonstrate that light possesses a higher probability to propagate in the liquid phase of a foam due to total
reflection. The authors term this observation photon channelling which we investigate in this article theoretically. We first
derive a central relation in the work of Gitting et al. without any free parameters. It links the photon's path-length fraction f in the liquid phase to the liquid fraction ɛ. We then construct two-dimensional Voronoi foams, replace the cell edges by
channels to represent the liquid films and simulate photon paths according to the laws of ray optics using transmission and
reflection coefficients from Fresnel's formulas. In an exact honeycomb foam, the photons show superdiffusive behavior. It
becomes diffusive as soon as disorder is introduced into the foams. The dependence of the diffusion constant on channel width
and refractive index is explained by a one-dimensional random-walk model. It contains a photon channelling state that is crucial
for the understanding of the numerical results. At the end, we shortly comment on the observation that photon channelling
only occurs in a finite range of ɛ. 相似文献
5.
E.G. Mishchenko M. Patra C.W.J. Beenakker 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):289-297
A theory is presented for the frequency dependence of the power spectrum of photon current fluctuations originating from a
disordered medium. Both the cases of an absorbing medium (“grey body”) and of an amplifying medium (“random laser”) are considered
in a waveguide geometry. The semiclassical approach (based on a Boltzmann-Langevin equation) is shown to be in complete agreement
with a fully quantum mechanical theory, provided that the effects of wave localization can be neglected. The width of the
peak in the power spectrum around zero frequency is much smaller than the inverse coherence time, characteristic for black-body
radiation. Simple expressions for the shape of this peak are obtained, in the absorbing case, for waveguide lengths large
compared to the absorption length, and, in the amplifying case, close to the laser threshold.
Received 8 August 2000 相似文献
6.
Preliminary analysis of surface radiation measurements recorded at the Nansen ice sheet (Antarctica)
Summary An experiment on radiation and surface energy balance was conducted during the 9th Italian expedition in Antarctica at the
Nansen ice sheet, a glacier situated close to the Italian base at Terra Nova Bay, to correlate surface balances to the formation
and development of katabatic winds. Measurements were taken by radiometers covering the whole spectra of solar and terrestrial
emissions and by fast sensors of atmospheric wind velocity and humidity for the application of the eddy correlation technique.
A preliminary analysis of the radiotive energy balance during the Antarctic summer in clear-sky conditions is reported and
discussed. The findings show the very low available energy (mean about 1 W/m2), in terms of net radiation, for the physical processes such as sensible- and latent-heat fluxes. Long-wave radiation balance
was applied to estimate the reliability of the Swinbank's parametrization, relative to general conditions of the atmosphere. 相似文献
7.
8.
P. Pellegrini O. Dulieu F. Masnou-Seeuws 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(1):77-86
This paper proposes a general method to investigate Feshbach resonances in atomic collisions similar to Cs(6
s
) + Cs(6
p
) in the thermal or cold regime. In order to compute the predissociation widths of the C
1
Π
u
(6
s
+ 5
d
) bound vibrational levels of Cs2, coupled both with the (2)
3
Σ
+
u
(6
s
+ 6
p
) continuum and with the (2)
3
Π
u
(6
s
+ 5
d
) vibrational series, a Fourier grid method is implemented, with an optical potential. A convenient way of optimizing the latter
is proposed. A large number of resonances are found and calculations of their cross-sections for stabilization into ground
state molecules show that the rate may be important. This confirms the interpretation of Lintz and Bouchiat [Phys. Rev. Lett.
80, 2570 (1998)] who observed dimer formation in cell experiments. Possible generalization to the cold regime relies on the
possibility to tune the position of a resonance to coincide with the maximum of the collisional energy distribution.
Received 14 February 2002 Published online 28 June 2002 相似文献