617 research outputs found
Inhibition of light tunneling for multichannel excitations in longitudinally modulated waveguide arrays
We consider evolution of multichannel excitations in longitudinally modulated
waveguide arrays where refractive index either oscillates out-of-phase in all
neighboring waveguides or when it is modulated in phase in several central
waveguides surrounded by out-of-phase oscillating neighbors. Both types of
modulations allow resonant inhibition of light tunneling, but only the
modulation of latter type conserves the internal structure of multichannel
excitations. We show that parameter regions where light tunneling inhibition is
possible depend on the symmetry and structure of multichannel excitations.
Antisymmetric multichannel excitations are more robust than their symmetric
counterparts and experience nonlinearity-induced delocalization at higher
amplitudes.Comment: 17 pages, 6 figures, to appear in Physical Review
Asymmetric solitons and domain walls supported by inhomogeneous defocusing nonlinearity
We show that an inhomogeneous defocusing nonlinearity that grows toward the
periphery in the positive and negative transverse directions at different rates
can support strongly asymmetric fundamental and multipole bright solitons,
which are stable in wide parameter regions. In the limiting case when
nonlinearity is uniform in one direction, solitons transform into stable domain
walls (fronts), with constant or oscillating intensity in the homogeneous
region, attached to a tail rapidly decaying in the direction of growing
nonlinearity.Comment: 3 pages, 5 figures, to appear in Optics Letter
Dynamics of platicons due to third-order dispersion
Dynamics of platicons caused by the third-order dispersion is studied. It is
shown that under the influence of the third-order dispersion platicons obtain
angular velocity depending both on dispersion and on detuning value. A method
of tuning of platicon associated optical frequency comb repetition rate is
proposed.Comment: 11 pages, 5 figure
Light bullets by synthetic diffraction-dispersion matching
We put forward a new approach to generate stable, fully three-dimensional
light bullets, which is based on the matching of the intrinsic material
dispersion with a suitable effective diffraction. The matching is achieved in
adequate waveguide arrays whose refractive index is periodically modulated
along the direction of light propagation. We show that by using
non-conventional, out-of-phase longitudinal modulation of the refractive index
of neighboring channels, it is possible to tune the effective diffraction to
match the intrinsic material group velocity dispersion. Three-dimensional light
bullets are shown to form at reduced energy levels, in settings where the
dispersion would be far too weak to generate bullets in the absence of array.Comment: 13 pages, 4 figures, to appear in Physical Review Letter
Generation of platicons and frequency combs in optical microresonators with normal GVD by modulated pump
We demonstrate that flat-topped dissipative solitonic pulses, platicons, and
corresponding frequency combs can be excited in optical microresonators with
normal group velocity dispersion using either amplitude modulation of the pump
or bichromatic pump. Soft excitation may occur in particular frequency range if
modulation depth is large enough and modulation frequency is close to the free
spectral range of the microresonator.Comment: 10 pages, 4 figures, to appear in EP
Dynamic versus Anderson wavepacket localization
We address the interplay between two fundamentally different wavepacket
localization mechanisms, namely resonant dynamic localization due to collapse
of quasi-energy bands in periodic media and disorder-induced Anderson
localization. Specifically, we consider light propagation in periodically
curved waveguide arrays on-resonance and off-resonance, and show that inclusion
of disorder leads to a gradual transition from dynamic localization to Anderson
localization, which eventually is found to strongly dominate. While in the
absence of disorder, the degree of localization depends critically on the
bending amplitude of the waveguide array, when the Anderson regime takes over
the impact of resonant effects becomes negligible.Comment: 13 pages, 5 figures, to appear in Physical Review
Stable nonlinear amplification of solitons without gain saturation
We demonstrate that the cubic gain applied in a localized region, which is
embedded into a bulk waveguide with the cubic-quintic nonlinearity and uniform
linear losses, supports stable spatial solitons in the absence of the quintic
dissipation. The system, featuring the bistability between the solitons and
zero state (which are separated by a family of unstable solitons), may be used
as a nonlinear amplifier for optical and plasmonic solitons, which, on the
contrary to previously known settings, does not require gain saturation. The
results are obtained in an analytical form and corroborated by the numerical
analysis.Comment: EPL, in pres
Solitons supported by singular spatial modulation of the Kerr nonlinearity
We introduce a setting based on the one-dimensional (1D) nonlinear
Schroedinger equation (NLSE) with the self-focusing (SF) cubic term modulated
by a singular function of the coordinate, |x|^{-a}. It may be additionally
combined with the uniform self-defocusing (SDF) nonlinear background, and with
a similar singular repulsive linear potential. The setting, which can be
implemented in optics and BEC, aims to extend the general analysis of the
existence and stability of solitons in NLSEs. Results for fundamental solitons
are obtained analytically and verified numerically. The solitons feature a
quasi-cuspon shape, with the second derivative diverging at the center, and are
stable in the entire existence range, which is 0 < a < 1. Dipole (odd) solitons
are found too. They are unstable in the infinite domain, but stable in the
semi-infinite one. In the presence of the SDF background, there are two
subfamilies of fundamental solitons, one stable and one unstable, which exist
together above a threshold value of the norm (total power of the soliton). The
system which additionally includes the singular repulsive linear potential
emulates solitons in a uniform space of the fractional dimension, 0 < D < 1. A
two-dimensional extension of the system, based on the quadratic nonlinearity,
is formulated too.Comment: Physical Review A, in pres
- …