90 research outputs found
Selective excitation of plasmons superlocalized at sharp perturbations of metal nanoparticles
Sharp metal corners and tips support plasmons localized on the scale of the
curvature radius -- superlocalized plasmons. We analyze plasmonic properties of
nanoparticles with small and sharp corner- and tip-shaped surface perturbations
in terms of hybridization of the superlocalized plasmons, which frequencies are
determined by the perturbations shape, and the ordinary plasmons localized on
the whole particle. When the frequency of a superlocalized plasmon gets close
to that of the ordinary plasmon, their strong hybridization occurs and
facilitates excitation of an optical hot-spot near the corresponding
perturbation apex. The particle is then employed as a nano-antenna that
selectively couples the free-space light to the nanoscale vicinity of the apex
providing precise local light enhancement by several orders of magnitude
Chirped dissipative solitons of the complex cubic-quintic nonlinear Ginzburg-Landau equation
Approximate analytical chirped solitary pulse (chirped dissipative soliton)
solutions of the one-dimensional complex cubic-quintic nonlinear
Ginzburg-Landau equation are obtained. These solutions are stable and
highly-accurate under condition of domination of a normal dispersion over a
spectral dissipation. The parametric space of the solitons is
three-dimensional, that makes theirs to be easily traceable within a whole
range of the equation parameters. Scaling properties of the chirped dissipative
solitons are highly interesting for applications in the field of high-energy
ultrafast laser physics.Comment: 20 pages, 12 figures, the mathematical apparatus is presented in
detail in http://info.tuwien.ac.at/kalashnikov/NCGLE2.htm
Nonlinear optical pulses in media with asymmetric gain
A generic novel model governing optical pulse propagation in a nonlinear
dispersive amplifying medium with asymmetric (linear spectral slope) gain is
introduced. We examine the properties of asymmetric optical pulses formed in
such gain-skewed media, both theoretically and numerically. We derive a
dissipative optical modification of the classical shallow water equations that
highlights an analogy between this phenomenon and hydrodynamic wave-breaking.
We observe the development of spectral optical shock waves, and discuss the
conditions and origins of this spectral wave-breaking in media with asymmetric
gain. These findings provide insight into the nature of asymmetric optical
pulses capable of accumulating large nonlinear phase without wave-breaking, a
crucial aspect in the design of nonlinear fiber amplifiers.Comment: 11 pages, 10 figure
Random mode coupling assists Kerr beam self-cleaning in a graded-index multimode optical fiber
In this paper, we numerically investigate the process of beam self-cleaning in a graded-index multimode optical fiber, by using the coupled-mode model. We introduce various models of random linear coupling between spatial modes, including coupling between all modes, or only between degenerate ones, and investigate the effects of random mode coupling on the beam self-cleaning process. The results of numerical investigations are in complete agreement with our experimental data
Nonlinear Optical Pulses in Media with Asymmetric Gain
A generic novel model governing optical pulse propagation in a nonlinear dispersive amplifying medium with asymmetric (linear spectral slope) gain is introduced. We examine the properties of asymmetric optical pulses formed in such gain-skewed media, both theoretically and numerically. We derive a dissipative optical modification of the classical shallow water equations that highlights an analogy between this phenomenon and hydrodynamic wave breaking. These findings provide insight into the nature of asymmetric optical pulses capable of accumulating large nonlinear phase without wave breaking, a crucial aspect in the design of nonlinear fiber amplifiers
Beam self-cleaning in multimode optical fibers and hydrodynamic 2D turbulence
We experimentally demonstrate the conservation of the average mode number in the process of Kerr beam self-cleaning in a graded-index multimode optical fiber, in analogy with wave condensation in hydrodynamic 2D turbulence
Giant Coulomb broadening and Raman lasing on ionic transitions
CW generation of anti-Stokes Raman laser on a number of blue-green argon-ion
lines (4p-4s, 4p-3d) has been demonstrated with optical pumping from metastable
levels 3d'^2G, 3d^4F. It is found, that the population transfer rate is
increased by a factor of 3-5 (and hence, the output power of such Raman laser)
owing to Coulomb diffusion in the velocity space. Measured are the excitation
and relaxation rates for the metastable level. The Bennett hole on the
metastable level has been recorded using the probe field technique. It has been
shown that the Coulomb diffusion changes shape of the contour to exponential
cusp profile while its width becomes 100 times the Lorentzian one and reaches
values close to the Doppler width. Such a giant broadening is also confirmed by
the shape of the absorption saturation curve.Comment: RevTex 18 pages, 5 figure
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