561 research outputs found
Optical bistability in a nonlinear photonic crystal waveguide notch filter
Optical bistability occurs when the effects of nonlinear behaviour of materials cause hysteresis in the transmission and reflection of a device. A possible mechanism for this is a strong dependence of the optical intensity on the index of refraction, e.g. in a cavity near resonance. In a 2- dimensional photonic crystal composed of rods of high-index material in air, a waveguide can be created by removing a line of rods. When a cavity is made by taking away several rods perpendicular to the waveguide, a notch filter characteristic in the transmission occurs. Due to the high intensity in the cavity in resonance, nonlinear effects are enhanced. This paper shows numerical simulations of bistability in the transmission and in the field inside the cavity both when a material inside the cavity has third-order (Kerr-type) nonlinear effects, and when the high-index rods themselves are nonlinear
Localization of Two-Component Bose-Einstein Condensates in Optical Lattices
We reveal underlying principles of nonlinear localization of a two-component
Bose-Einstein condensate loaded into a one-dimensional optical lattice. Our
theory shows that spin-dependent optical lattices can be used to manipulate
both the type and magnitude of nonlinear interaction between the ultracold
atomic species and to observe nontrivial two-componentnlocalized states of a
condensate in both bands and gaps of the matter-wave band-gap structure.Comment: 4 pages, 4 figure
Simple and efficient generation of gap solitons in Bose-Einstein condensates
We suggest an efficient method for generating matter-wave gap solitons in a
repulsive Bose-Einstein condensate, when the gap soliton is formed from a
condensate cloud in a harmonic trap after turning on a one-dimensional optical
lattice. We demonstrate numerically that this approach does not require
preparing the initial atomic wave packet in a specific state corresponding to
the edge of the Brillouin zone of the spectrum, and losses that occur during
the soliton generation process can be suppressed by an appropriate adiabatic
switching of the optical lattice.Comment: 7 pages, 10 figure
Nonlinear Aharonov-Bohm scattering by optical vortices
We study linear and nonlinear wave scattering by an optical vortex in a
self-defocusing nonlinear Kerr medium. In the linear case, we find a splitting
of a plane-wave front at the vortex proportional to its circulation, similar to
what occurs in the scattered wave of electrons for the Aharonov-Bohm effect.
For larger wave amplitudes, we study analytically and numerically the
scattering of a dark-soliton stripe (a nonlinear analog of a small-amplitude
wavepacket) by a vortex and observe a significant asymmetry of the scattered
wave. Subsequently, a wavefront splitting of the scattered wave develops into
transverse modulational instability, ``unzipping'' the stripe into trains of
vortices with opposite charges.Comment: 4 pages, 4 figure
Nonlinear metal-dielectric nanoantennas for light switching and routing
We introduce a novel hybrid metal-dielectric nanoantenna composed of
dielectric (crystalline silicon) and metal (silver) nanoparticles. A
high-permittivity dielectric nanoparticle allows to achieve effective light
harvesting, and nonlinearity of a metal nanoparticle controls the radiation
direction. We show that the radiation pattern of such a nanoantenna can be
switched between the forward and backward directions by varying only the light
intensity around the level of 11 MW/cm, with the characteristic switching
time of 260 fs.Comment: 9 pages, 5 figures, submitted to New J. Phy
Discreteness-Induced Oscillatory Instabilities of Dark Solitons
We reveal that even weak inherent discreteness of a nonlinear model can lead
to instabilities of the localized modes it supports. We present the first
example of an oscillatory instability of dark solitons, and analyse how it may
occur for dark solitons of the discrete nonlinear Schrodinger and generalized
Ablowitz-Ladik equations.Comment: 11 pages, 4 figures, to be published in Physical Review Letter
Coupled-mode theory for spatial gap solitons in optically-induced lattices
We develop a coupled-mode theory for spatial gap solitons in the
one-dimensional photonic lattices induced by interfering optical beams in a
nonlinear photorefractive crystal. We derive a novel system of coupled-mode
equations for two counter-propagating probe waves, and find its analytical
solutions for stationary gap solitons. We also predict the existence of moving
(or tilted) gap solitons and study numerically soliton collisions.Comment: 3 pages, submitted to Optics Letter
Square vortex solitons with a large angular momentum
We show the existence of square shaped optical vortices with a large value of
the angular momentum hosted in finite size laser beams which propagate in
nonlinear media with a cubic-quintic nonlinearity. The light profiles take the
form of rings with sharp boundaries and variable sizes depending on the power
carried. Our stability analysis shows that these light distributions remain
stable when propagate, probably for unlimited values of the angular momentum,
provided the hosting beam is wide enough. This happens if the peak amplitude
approaches a critical value which only depends on the nonlinear refractive
index of the material. A variational approach allows us to calculate the main
parameters involved. Our results add extra support to the concept of surface
tension of light beams that can be considered as a trace of the existence of a
liquid of light.Comment: 6 pages, 6 figures, submitted to Phys. Rev.
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