arXiv subjects

Lluis Torner

Publications and source records attributed to Lluis Torner.

At least 109 records · Page 6Linked to original sources

arXiv2010

A method to generate complex quasi-nondiffracting optical lattices

We put forward a powerful technique that allows generating quasi-non-diffracting light beams with a variety of complex transverse shapes and topologies. We show that, e.g., spiraling patterns, patterns featuring curved or bent bright stripes, or patterns featuring arbitrary combinations of harmonic, Bessel, Mathieu and parabolic beams occupying different domains in the transverse plane can be produced. The quasi-non-diffracting patterns open up a wealth of opportunities for the manipulation of matter and optical waves, colloidal and living particles, with applications in biophysics, and quantum, nonlinear and atom optics.

physics.optics↗

arXiv2010

Stabilization of two-dimensional solitons in cubic-saturable nonlinear lattices

We consider soliton dynamics and stability in a nonlinear lattice formed by alternating domains with focusing cubic and saturable nonlinearities. We find that in such lattices solitons centered on cubic domains may be stabilized even in two-dimensional geometries, in spite of their intrinsic catastrophic instability in the absence of the lattice. Solitons centered on saturable domains are always unstable.

physics.optics↗

arXiv2010

Twin-vortex solitons in nonlocal nonlinear media

We consider soliton formation in thermal nonlinear media bounded by rectangular cross-sections and uncover a new class of nonlinear stationary topological state. Specifically, we find that stationary higher-order vortex states in standard shapes do not exist, but rather they take the form of multiple, spatially separated single-charge singularities nested in an elliptical beam. Double-charge states are found to be remarkably robust despite their shape asymmetry and the phase-singularity splitting. States with higher topological charges are found to be unstable.

physics.optics↗

arXiv2009

Polarization conversion spectroscopy of hybrid modes

Enhanced polarization conversion in reflection for the Otto and Kretschmann configurations is introduced as a new method for hybrid-mode spectroscopy. Polarization conversion in reflection appears when hybrid-modes are excited in a guiding structure composed of at least one anisotropic media. In contrast to a dark dip, in this case modes are associated to a peak in the converted reflectance spectrum, increasing the detection sensitivity and avoiding confusion with reflection dips associated with other processes as can be transmission.

cond-mat.mtrl-sci↗

arXiv2009

Vector solitons in nonlinear lattices

We consider two-component solitons in a medium with a periodic modulation of the nonlinear coefficient. The modulation enables the existence of complex multihump vector states. In particular, vector solitons composed of dipole and fundamental, or dipole and even double-hump components exist and may be stable. Families of unstable scalar solitons can be stabilized in the vectorial form, due to the coupling to a stable second component.

physics.optics↗

arXiv2009

Stabilization of multi-beam necklace solitons in circular arrays with spatially modulated nonlinearity

We address necklace solitons supported by circular waveguide arrays with out-of-phase modulation of nonlinearity and linear refractive index. Such two-dimensional necklace solitons appear as rings of multiple out-of-phase bright spots. We show that necklace solitons are stable if their peak intensity is low or moderate and that the domain of stability shrinks with increasing nonlinearity modulation depth. However, we find that the stability domains expand with increasing number of necklace spots.

physics.optics↗

arXiv2009

Power-dependent soliton steering in thermal nonlinear media

We address the existence and properties of optical solitons excited in thermal nonlinear media with a transverse refractive index gradient. We show that in such a geometry one can generate controllable switching from surface soliton propagating near the sample edges to bulk solitons. Beam steering associated to the different soliton output locations can be achieved by varying the input light intensity.

physics.optics↗

arXiv2009

Soliton shape and mobility control in optical lattices

We present a progress overview focused on the recent theoretical and experimental advances in the area of soliton manipulation in optical lattices. Optical lattices offer the possibility to engineer and to control the diffraction of light beams in media with periodically-modulated optical properties, to manage the corresponding reflection and transmission bands, and to form specially designed defects. Consequently, they afford the existence of a rich variety of new families of nonlinear stationary waves and solitons, lead to new rich dynamical phenomena, and offer novel conceptual opportunities for all-optical shaping, switching and routing of optical signals encoded in soliton formats. In this overview, we consider reconfigurable optically-induced lattices as well as waveguide arrays made in suitable nonlinear materials. We address both, one-dimensional and multi-dimensional geometries. We specially target the new possibilities made possible by optical lattices induced by a variety of existing non-diffracting light patterns, we address nonlinear lattices and soliton arrays, and we briefly explore the unique features exhibited by light propagation in defect modes and in random lattices, an area of current topical interest and of potential cross-disciplinary impact.

physics.optics↗

arXiv2009

Light bullets in Bessel optical lattices with spatially modulated nonlinearity

We address the stability of light bullets supported by Bessel optical lattices with out-of-phase modulation of the linear and nonlinear refractive indices. We show that spatial modulation of the nonlinearity significantly modifies the shapes and stability domains of the light bullets. The addressed bullets can be stable, provided that the peak intensity does not exceed a critical value. We show that the width of the stability domain in terms of the propagation constant may be controlled by varying the nonlinearity modulation depth. In particular, we show that the maximum energy of the stable bullets grows with increasing nonlinearity modulation depth.

nlin.PS↗

arXiv2009

Walking vector soliton caging and releasing

We address the formation and propagation of vector solitons in optical lattices in the presence of anisotropy-induced walk-off between ordinary and extraordinary polarized field components. Stable vector solitons trapped by the lattice form above a threshold power, while decreasing the lattice depth below a critical value results in the abrupt release of the caged solitons, that then move across the lattice and may get trapped in a desired lattice channel.

physics.optics↗

arXiv2009

Parametric amplification of random lattice soliton swinging

We consider the propagation of solitons in media with an imprinted transverse periodic or parabolic refractive index modulation when the modulation depth slightly fluctuates along the propagation direction. We find that, under suitable spectral resonance conditions, small transverse soliton oscillations may get parametrically amplified.

physics.optics↗

arXiv2009

Light bullets in optical tandems

We address the concept of three-dimensional light bullet formation in structures where nonlinearity and dispersion are contributed by different materials, including metamaterials, which are used at their best to create suitable conditions where bullets can form. The particular geometry considered here consists of alternating rings made of highly dispersive but weakly nonlinear media and strongly nonlinear but weakly dispersive media. We show that light bullets form for a wide range of parameters.

physics.optics↗

arXiv2009

Engineering soliton nonlinearities: From local to strongly nonlocal

We put forward a strategy to achieve synthetic nonlinearities where local and nonlocal contributions compete on similar footing, thus yielding intermediate tunable responses ranging from fully local to strongly nonlocal. The physical setting addressed is a semiconductor material with both Kerr and thermal nonlinearities illuminated by a pulse train with suitable single-pulse width and repetition rate. We illustrate the potential of the scheme by showing that it supports soliton properties that are not accessible in either limit of purely local or purely nonlocal media.

physics.optics↗

arXiv2009

Stable two-dimensional solitons in nonlinear lattices

We address the existence and stability of two-dimensional solitons in optical or matter-wave media, which are supported by purely nonlinear lattices in the form of a periodic array of cylinders with self-focusing nonlinearity, embedded into a linear material. We show that such lattices can stabilize two-dimensional solitons against collapse. We also found that stable multipoles and vortex solitons are also supported by the nonlinear lattices, provided that the nonlinearity exhibits saturation.

physics.optics↗

arXiv2008

Multipole surface solitons in layered thermal media

We address the existence and properties of multipole solitons localized at a thermally insulating interface between uniform or layered thermal media and a linear dielectric. We find that in the case of uniform media, only surface multipoles with less than three poles can be stable. In contrast, we reveal that periodic alternation of the thermo-optic coefficient in layered thermal media makes possible the stabilization of higher order multipoles.

physics.optics↗

arXiv2008

Stabilization of higher-order vortices and multi-hump solitons in media with synthetic nonlocal nonlinearities

We address the evolution of higher-order excited states, such as vortex and multi-hump solitons, in nonlocal media with synthetic, competing focusing and defocusing nonlinearities with different nonlocal transverse scales. We reveal that introduction of suitable competing effects makes possible the stabilization of vortex solitons with topological charge m>2, as well as one-dimensional multi-hump solitons with number of humps p>4, all of which are highly unstable in natural nonlocal materials with focusing nonlinearities.

physics.optics↗

arXiv2008

Gap solitons on a ring

We introduce a new species of gap solitons (GSs) supported by an azimuthally modulated guiding ring in defocusing cubic media. The periodicity in the azimuthal direction strongly modifies properties and existence domains of GSs. In addition to the fundamental solitons, we report even and twisted bound states. The former type is found to be stable, while the twisted states are always unstable in defocusing media.

physics.optics↗

arXiv2008

Power-dependent shaping of vortex solitons in optical lattices with spatially modulated nonlinear refractive index

We address vortex solitons supported by optical lattices featuring modulation of both the linear and nonlinear refractive indices. We find that when the modulation is out-of-phase the competition between both effects results in remarkable shape transformations of the solitons which profoundly affect their properties and stability. Nonlinear refractive index modulation is found to impose restrictions on the maximal power of off-site solitons, which are shown to be stable only below a maximum nonlinearity modulation depth.

physics.optics↗