Observation of optical spatial solitons in a highly nonlocal medium

Incoherent solitons in instantaneous nonlocal nonlinear media

We predict random-phase spatial solitons in instantaneous nonlocal nonlinear media. The key mechanism responsible for self-trapping of such incoherent wave packets is played by the nonlocal (rather than the traditional noninstantaneous) nature of the nonlinearity. This kind of incoherent soliton has profoundly different features than other incoherent solitons.

Discrete light localization in one-dimensional nonlinear lattices with arbitrary nonlocality

We model discrete spatial solitons in a periodic nonlinear medium encompassing any degree of transverse nonlocality. Making a convenient reference to a widely used material--nematic liquid crystals--we derive a form of the discrete nonlinear Schrödinger equation and find a family of discrete solitons. Such self-localized solutions in optical lattices can exist with an arbitrary degree of imprinted chirp and have breathing character. We verify numerically that both local and nonlocal discrete light propagation and solitons can be observed in liquid crystalline arrays.

Theory of nonlocal soliton interaction in nematic liquid crystals

We investigate interactions between spatial nonlocal bright solitons in nematic liquid crystals using an analytical ("effective particle") approach as well as direct numerical simulations. The model predicts attraction of out-of-phase solitons and the existence of their stable bound state. This nontrivial property is solely due to the nonlocal nature of the nonlinear response of the liquid crystals. We further predict and verify numerically the critical outwards angle and degree of nonlocality which determine the transition between attraction and repulsion of out-of-phase solitons.

Spatial solitons and modulational instability in the presence of large birefringence: the case of highly nonlocal liquid crystals

With reference to spatially nonlocal nematic liquid crystals, we develop a theory of optical spatial solitons and modulational instability in anisotropic media with arbitrarily large birefringence. Asymmetric spatial profiles and multivalued features are predicted for self-localized light versus walk-off angle. The results hold valid for generic self-focusing birefringent media and apply to large angle steering of individual and multiple self-trapped optical beams.

Optical spatial solitons in soft matter

We predict that spatial self-trapping of light can occur in soft matter encompassing a wide class of new materials such as colloids, foams, gels, fractal aggregates, etc. We develop a general nonlocal theory that allows one to relate the properties of the trapped state of Maxwell equations to the measurable static structure factor of the specific material. We give numerical evidence for stable trapping in fractal aggregates and suggest also the possibility of soliton spectroscopy of soft matter.

Nonlocal incoherent white-light solitons in logarithmically nonlinear media

The propagation properties of white-light solitons in spatially nonlocal media with a logarithmically nonlinearity are investigated theoretically. The existence curve of the stationary nonlocal incoherent soliton is obtained and the coherence characteristics of the soliton are also described. The evolution behaviors of the nonlocal white-light soliton are discussed in detail by both approximate analytical solution and numerical simulation when the solitons undergo periodic oscillation.

Soliton mobility in nonlocal optical lattices

We address the impact of nonlocality in the physical features exhibited by solitons supported by Kerr-type nonlinear media with an imprinted optical lattice. We discover that the nonlocality of the nonlinear response can profoundly affect the soliton mobility, hence all the related phenomena. Such behavior manifests itself in significant reductions of the Peierls-Nabarro potential with an increase in the degree of nonlocality, a result that opens the rare possibility in nature of almost radiationless propagation of highly localized solitons across the lattice.

Stable vortex solitons in nonlocal self-focusing nonlinear media

We reveal that spatially localized vortex solitons become stable in self-focusing nonlinear media when the vortex symmetry-breaking azimuthal instability is eliminated by a nonlocal nonlinear response. We study the main properties of different types of vortex beams and discuss the physical mechanism of the vortex stabilization in spatially nonlocal nonlinear media.

Self-healing generation of spatial solitons in liquid crystals

We demonstrate that, in suitably designed cells with undoped nematic liquid crystals, extraordinary-wave spatial solitons can be excited at every applied voltage without adjustments in the input polarization. Their walk-off, hence direction of propagation, is externally controlled over angles as large as 7 degrees. The results pave the way not only to polarization-forgiving generation but also to voltage readdressing of these extraordinary-wave nematicons.

Discrete light propagation and self-trapping in liquid crystals

We investigate light propagation and self-localization in a voltage-controlled array of channel waveguides realized in undoped nematic liquid crystals. We report on discrete diffraction and solitons, as well as all-optical angular steering and the formation of multiband vector breathers. The results and are in excellent agreement with both coupled mode theory and full numerical simulations.

Interplay between nonlocality and nonlinearity in nematic liquid crystals

Spatial nonlocality has a crucial role in the optical response of bulk liquid crystals. With specific reference to one-dimensional modulation instability, we demonstrate the tuning of transverse nonlocality in the nonlinear response of nematics.

Optical multiband vector breathers in tunable waveguide arrays

We investigate multiband optical breathers in a voltage-adjustable array of coupled waveguides in nematic liquid crystals. Symmetric breathers resulting from vector composition of modes from two bands are observed over large propagation distances and are described in terms of the Floquet-Bloch theory.

Routing of anisotropic spatial solitons and modulational instability in liquid crystals

In certain materials, the spontaneous spreading of a laser beam (owing to diffraction) can be compensated for by the interplay of optical intensity and material nonlinearity. The resulting non-diffracting beams are called 'spatial solitons' (refs 1-3), and they have been observed in various bulk media. In nematic liquid crystals, solitons can be produced at milliwatt power levels and have been investigated for both practical applications and as a means of exploring fundamental aspects of light interactions with soft matter. Spatial solitons effectively operate as waveguides, and so can be considered as a means of channelling optical information along the self-sustaining filament. But actual steering of these solitons within the medium has proved more problematic, being limited to tilts of just a fraction of a degree. Here we report the results of an experimental and theoretical investigation of voltage-controlled 'walk-off' and steering of self-localized light in nematic liquid crystals. We find not only that the propagation direction of individual spatial solitons can be tuned by several degrees, but also that an array of direction-tunable solitons can be generated by modulation instability. Such control capabilities might find application in reconfigurable optical interconnects, optical tweezers and optical surgical techniques.

Nonlocal incoherent solitons

We investigate the propagation of partially coherent beams in spatially nonlocal nonlinear media with a logarithmic type of nonlinearity. We derive analytical formulas for the evolution of the beam parameters and conditions for the formation of nonlocal incoherent solitons.