12,412 research outputs found
On negative higher-order Kerr effect and filamentation
As a contribution to the ongoing controversy about the role of higher-order
Kerr effect (HOKE) in laser filamentation, we first provide thorough details
about the protocol that has been employed to infer the HOKE indices from the
experiment. Next, we discuss potential sources of artifact in the experimental
measurements of these terms and show that neither the value of the observed
birefringence, nor its inversion, nor the intensity at which it is observed,
appear to be flawed. Furthermore, we argue that, independently on our values,
the principle of including HOKE is straightforward. Due to the different
temporal and spectral dynamics, the respective efficiency of defocusing by the
plasma and by the HOKE is expected to depend substantially on both incident
wavelength and pulse duration. The discussion should therefore focus on
defining the conditions where each filamentation regime dominates.Comment: 22 pages, 11 figures. Submitted to Laser physics as proceedings of
the Laser Physics 2010 conferenc
Parametric Resonance Phenomena in Bose-Einstein Condensates: Enhanced Quantum Tunneling of Coherent Matter Pulses
We investigate the quantum tunneling of a Bose-Einstein condensate confined
in a optical trap. We show that periodic pulses of coherent matter are emitted
from the trap by using an oscillating energy barrier. Moreover, the emitted
fraction of condensed atoms strongly increases if the period of oscillation of
the height of the energy barrier is in parametric resonance with the period of
oscillation of the center of mass of the condensate inside the potential well.
Our model is analyzed by numerically solving the nonpolynomial Schrodinger
equation (NPSE), an effective one-dimensional equation which describes the
macroscopic wavefunction of Bose condensates under transverse harmonic
confinement. The range of validity of NPSE is discussed and compared with that
of Gross-Pitaevskii equation.Comment: 11 pages, 2 figures, presented to the 'Laser Physics Workshop 2002',
seminar on 'Bose-Einstein Condensation of Trapped Atoms', Bratislava, July
2002, to be published in Laser Physics; related papers can be found at
http://www.mi.infm.it/salasnich/tdqg.htm
How Does a Dipolar Bose-Einstein Condensate Collapse?
We emphasize that the macroscopic collapse of a dipolar Bose-Einstein
condensate in a pancake-shaped trap occurs through local density fluctuations,
rather than through a global collapse to the trap center. This hypothesis is
supported by a recent experiment in a chromium condensate.Comment: Proceedings of 17th International Laser Physics Worksho
Ray transfer matrix for a spiral phase plate
We present a ray transfer matrix for a spiral phase plate. Using this matrix,
we determine the stability of an optical resonator made of two spiral phase
plates, and trace stable ray orbits in the resonator. Our results should be
relevant to laser physics, optical micromanipulation, quantum information and
optomechanics.Comment: 5 pages, 3 figure
Ytterbium- and chromium-doped fibre laser: from chaotic self-pulsing to passive Q-switching
A spontaneously chaotic, self-pulsing ytterbium-doped fibre laser is
partially stabilized into the passively Q-switched mode of operation using a
chromium-doped saturable absorber fibre. This original all-fibre laser produces
sustained and stable trains of smooth pulses at high repetition rate.Comment: 1 page abstract; at 20th International laser physics workshop,
Sarajevo : Bosnia And Herzegovina (2011
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