1,109 research outputs found
Discrete light localization in one dimensional nonlinear lattices with arbitrary non locality
We model discrete spatial solitons in a periodic nonlinear medium
encompassing any degree of transverse non locality. Making a convenient
reference to a widely used material -nematic liquid crystals-, we derive a new
form of the discrete nonlinear Schrodinger equation and find a novel family of
discrete solitons. Such self-localized solutions in optical lattices can exist
with an arbitrary degree of imprinted chirp and a have breathing character. We
verify numerically that both local and non local discrete light propagation and
solitons can be observed in liquid crystalline arrays.Comment: Extended version with 6 pages and 4 Figures, to appear in Phys. Rev.
Breather solitons in highly nonlocal media
We investigate the breathing of optical spatial solitons in highly nonlocal
media. Generalizing the Ehrenfest theorem, we demonstrate that oscillations in
beam width obey a fourth-order ordinary differential equation. Moreover, in
actual highly nonlocal materials, the original accessible soliton model by
Snyder and Mitchell [Science \textbf{276}, 1538 (1997)] cannot accurately
describe the dynamics of self-confined beams as the transverse size
oscillations have a period which not only depends on power but also on the
initial width. Modeling the nonlinear response by a Poisson equation driven by
the beam intensity we verify the theoretical results against numerical
simulations.Comment: 7 pages, 4 figures, resubmitted to Physical Review
Electromagnetic confinement via spin-orbit interaction in anisotropic dielectrics
We investigate electromagnetic propagation in uniaxial dielectrics with a
transversely varying orientation of the optic axis, the latter staying
orthogonal everywhere to the propagation direction. In such a geometry, the
field experiences no refractive index gradients, yet it acquires a
transversely-modulated Pancharatnam-Berry phase, that is, a geometric phase
originating from a spin-orbit interaction. We show that the periodic evolution
of the geometric phase versus propagation gives rise to a
longitudinally-invariant effective potential. In certain configurations, this
geometric phase can provide transverse confinement and waveguiding. The
theoretical findings are tested and validated against numerical simulations of
the complete Maxwell's equations. Our results introduce and illustrate the role
of geometric phases on electromagnetic propagation over distances well
exceeding the diffraction length, paving the way to a whole new family of
guided waves and waveguides which do not rely on refractive index tailoring.Comment: 16 pages, 4 figure
Incoherent interaction of nematicons in bias-free liquid-crystal cells
We study experimentally the propagation dynamics and interaction of a pair of
mutually incoherent nematicons: spatial optical solitons in nematic liquid
crystals. In contrast to earlier studies, we consider a bias-free
liquid-crystal cell and compare the soliton interaction in copropagating and
counterpropagating geometries. We analyze the dependence of nematicon
interaction on input power and observe a direct manifestation of a long-range
nonlocal nonlinearity. Attraction of counterpropagating solitons requires
higher powers and longer relaxation times than that of copropagating nematicons
due to losses-induced power asymmetry of counterpropagating nematicons.Comment: 5 pages, z figure
Quadratic phase matching in slot waveguides
We analyze phase matching with reference to frequency doubling in nanosized
quadratic waveguides encompassing form birefringence and supporting
cross-polarized fundamental and second-harmonic modes. In an AlGaAs rod with an
air void, we show that phase-matched second-harmonic generation could be
achieved in a wide spectral range employing state-of-the-art nanotechnology.Comment: 3 pages, 4 figure
Spin-optical solitons in liquid crystals
© 2020 American Physical Society. In the framework of nonlinear spin optics, we investigate self-confined light beams in reorientational nematic liquid crystals. Using modulation theory and numerical experiments, we analyze spatial solitary waves supported by the geometric phase arising in a uniaxial when subject to a nonlinear modulation of its optic axis distribution. Spin evolution and optical reorientation in an index-homogeneous medium give rise to a longitudinally periodic, transversely inhomogeneous potential able to counteract the diffraction of a polarized bell-shaped beam, generating a spin-optical solitary wave. Spin-optical solitary waves evolve in polarization and have an oscillatory character in amplitude, size, and ellipticity
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