Observation of two-dimensional nonlocal gap solitons.

We demonstrate, both theoretically and experimentally, the existence of nonlocal gap solitons in two-dimensional periodic photonic structures with defocusing thermal nonlinearity. We employ liquid-infiltrated photonic crystal fibers and show how the system geometry can modify the effective response of a nonlocal medium and the properties of two-dimensional gap solitons.

Tunable diffraction and self-defocusing in liquid-filled photonic crystal fibers.

We suggest and demonstrate a novel platform for the study of tunable nonlinear light propagation in two-dimensional discrete systems, based on photonic crystal fibers filled with high index nonlinear liquids. Using the infiltrated cladding region of a photonic crystal fiber as a nonlinear waveguide array, we experimentally demonstrate highly tunable beam diffraction and thermal self-defocusing, and realize a compact all-optical power limiter based on a tunable nonlinear response.

Observation of nonlinear self-trapping in triangular photonic lattices.

We experimentally study light self-trapping in triangular photonic lattices induced optically in nonlinear photorefractive crystals. We observe the formation of two-dimensional discrete and gap spatial solitons originating from the first and second bands of the linear transmission spectrum.

Observation of surface gap solitons in semi-infinite waveguide arrays.

We report on the observation of surface gap solitons found to exist at the interface between uniform and periodic dielectric media with defocusing nonlinearity. We demonstrate strong self-trapping at the edge of a LiNbO3 waveguide array and the formation of staggered surface solitons with propagation constant inside the first photonic band gap. We study the crossover between linear repulsion and nonlinear attraction at the surface, revealing the mechanism of nonlinearity-mediated stabilization of the surface gap modes.

Demonstration of all-optical beam steering in modulated photonic lattices.

We demonstrate experimentally all-optical beam steering in modulated photonic lattices induced optically by three-beam interference in a biased photorefractive crystal. We identify and characterize the key physical parameters governing the beam steering and show that the spatial resolution can be enhanced by the additional effect of nonlinear beam self-localization.

Crossover from self-defocusing to discrete trapping in nonlinear waveguide arrays.

We predict a sharp crossover from nonlinear self-defocusing to discrete self-trapping of a narrow Gaussian beam with the increase of the refractive index contrast in a periodic photonic lattice. We demonstrate experimentally nonlinear discrete localization of light with defocusing nonlinearity by single site excitation in LiNbO(3) waveguide arrays.

Tunable positive and negative refraction in optically induced photonic lattices.

We study tunable refraction of light in one-dimensional periodic lattices induced optically in a photorefractive crystal. We observe experimentally both positive and negative refraction of beams that selectively excite the first or second spectral bands of the periodic lattice, and we demonstrate tunability of the output beam position by dynamically adjusting the lattice depth. At higher laser intensities, beam broadening due to diffraction can be suppressed through nonlinear self-focusing while preserving the general steering properties.