V. M. Shandarov

Observation of bright spatial photorefractive solitons in a planar strontium barium niobate waveguide

We have obtained stationary bright spatial solitons in a planar photorefractive strontium barium niobate waveguide for visible light ranging from 514.5 to 780 nm. Even for larger wavelengths (lambda=1047 nm) strong self-focusing of the beam was observed; however, input power had to be some orders of magnitude higher than for visible light for self-focusing to occur. Furthermore, we found transient self-trapping of red light (lambda=632.8 nm) that corresponds to the formation of bright quasi-steady-state solitons.

Observation of dark spatial photovoltaic solitons in planar waveguides in lithium niobate

We have obtained photovoltaic lenses and dark spatial solitons in planar optical waveguides in lithium niobate doped with iron and copper. For TE modes of lower indices the photovoltaic nonlinearity only partly decreased the width of a dark notch within the outcoupled image of the recording light beam. The corresponding time to reach a steady state of this light-induced change ranged from about 0.1 to 30 s depending on the waveguide sample. For higher modes we observed a full compensation of the divergence of the dark notch on a time scale of some minutes. In some cases this was followed by an extinction of the dark solitons because the light was over-defocused in the highest modes.

Thermally induced self-focusing and optical beam interactions in planar strontium barium niobate waveguides

We present an experimental study of thermally induced self-focusing effects and interactions of incoherent light beams in strontium barium niobate waveguides. Depending on the input power, a single parallel beam is strongly focused inside the sample up to diameters of several micrometers. For higher input power we observe the splitting of the beam in a sequence of several spots. We demonstrate that these thermally induced refractive-index patterns can be used to focus and deflect an incoherent guided probe beam in the waveguide with time constants below 1 ms.

Formation of reconfigurable optical channel waveguides and beam splitters on top of proton-implanted lithium niobate crystals using spatial dark soliton-like structures

We report on the formation of reconfigurable optical channel waveguides (including straight stripes and Y-branches) on top of iron-doped lithium niobate crystals. The sample surface is first implanted by 500 keV protons to form a planar waveguide showing a propagation loss of ~1.6 dB cm−1 after modest post-implantation annealing. Afterwards, the sample surface is illuminated with well-defined stripe patterns (straight channels, beam splitters) of green light using lithographic masks. Due to the photovoltaic effect in lithium niobate resulting in negative index changes in illuminated regions, waveguide layers are formed in the non-illuminated regions perpendicular to the planar waveguide in the same way as it occurs in the dark spatial soliton regime. In this way two-dimensional waveguides are formed in the overlap region on top of the crystal that may be used for reconfigurable optical interconnections and splitters.

Observation of discrete gap solitons in one-dimensional waveguide arrays with alternating spacings and saturable defocusing nonlinearity.

We consider, both experimentally and theoretically, the existence and stability of localized, symmetric, and antisymmetric gap solitons (GSs) in binary lattices of identical waveguides but with alternating spacings. Furthermore, the properties of surface GSs at the boundary of the lattice are explored.

Quasi-one-dimensional photonic lattices and superlattices in lithium niobate: Linear and nonlinear discrete diffraction of light

The effects of linear and nonlinear light propagation in quasi-one-dimensional systems of coupled optical waveguides (photonic lattices and superlattices) obtained by projection optical induction in photorefractive lithium niobate samples have been experimentally studied and numerically simulated.

Discrete Diffraction and Spatial Self-Action of Light Beams in One-Dimensional Photonic Lattices in Lithium Niobate

Features of the behavior of light beams in one-dimensional photonic lattices in iron-doped lithium niobate have been experimentally studied. It is demonstrated that bright discrete spatial solitons and bright gap solitons can be formed in this system using 633 nm radiation on a microwatt power level.

Linear and nonlinear light propagation at the interface of two homogeneous waveguide arrays

We investigate linear and nonlinear light propagation at the interface of two one-dimensional homogeneous waveguide arrays containing a single defect of different strength. For the linear case and in a limited region of the defect size, we find trapped staggered and unstaggered modes. In the nonlinear case, we study the dependence of power thresholds for discrete soliton formation in different channels as a function of defect strength. All experimental results are confirmed theoretically using an adequate discrete model.

Transformation of the amplitude profiles of coherent light beams in a nonlinear photorefractive Fabry-Perot interferometer

The transformations of the transverse profiles of laser beams in a nonlinear Fabry-Perot interferometer based on lithium niobate crystals with a surface layer doped with a combination of photorefractive impurities (iron and copper ions) have been experimentally investigated. It is demonstrated that the distribution of transmitted beam intensity significantly changes for a few seconds at milliwatt beam powers.

Linear and nonlinear light localization within photorefractive photonic superlattices in lithium niobate

Some features of discrete diffraction of light, which manifest themselves in the possibility of its linear and nonlinear localization in one or several waveguide elements, in photorefractive photonic superlattices optically induced in lithium niobate crystals, and in planar optical waveguides based on this material, have been experimentally investigated.