Aleksandra I. Strinić

Transverse modulational instabilities of counterpropagating solitons in photorefractive crystals

We study numerically the counterpropagating vector solitons in SBN:60 photorefractive crystals. A simple theory is provided for explaining the symmetry-breaking transverse instability of these solitons. Phase diagram is produced that depicts the transition from stable counterpropagating solitons to bidirectional waveguides to unstable optical structures. Numerical simulations are performed that predict novel dynamical beam structures, such as the standing-wave and rotating multipole vector solitonic clusters. For larger coupling strengths and/or thicker crystals the beams form unstable self-trapped optical structures that have no counterparts in the copropagating geometry.

Counterpropagating self-trapped beams in photorefractive crystals

A time-dependent model for the formation of self-trapped optical beams in photorefractive media by counterpropagating laser beams is analysed. It is shown that dynamically the beams may form stable steady-state structures or display periodic and irregular temporal behaviour. Steady-state solutions of non-uniform cross section are found, representing a general class of self-trapped waveguides, that include counterpropagating spatial vector solitons as a particular case. Two critical curves are identified in the plane of parameters, the first one separating vector solitons from the stable bidirectional waveguides and the second one separating stable waveguides from the unstable ones. Dynamically stable rotating beam structures are discovered that have no analogues in the usual steady-state theory of spatial solitons.

Interactions in large arrays of solitons in photorefractive crystals

Large two-dimensional spatial soliton arrays are generated experimentally and numerically in photorefractive media and their waveguiding properties at red and infrared wavelengths are demonstrated. An enhanced stability of solitonic lattices is achieved by exploiting the anisotropy of coherent soliton interaction and by controlling the relative phase between soliton rows. Manipulation of individual solitonic channels is accomplished by the use of separate control beams.

Comment on “Spatial optical solitons in highly nonlocal media”

In a recent paper [A. Alberucci, C. Jisha, N. Smyth, and G. Assanto, Phys. Rev. A 91, 013841 (2015)], Alberucci et al. have studied the propagation of bright spatial solitary waves in highly nonlocal media. We find that the main results in that and related papers, concerning soliton shape and dynamics, based on the accessible soliton (AS) approximation, are incorrect; the correct results have already been published by others. These and other inconsistencies in the paper follow from the problems in applying the AS approximation in earlier papers by the group that propagated to the later papers. The accessible soliton theory cannot describe accurately the features and dynamics of solitons in highly nonlocal media.

Finite-size effects in fundamental solitons in highly nonlocal nematic liquid crystals

We investigate numerically solitons in highly nonlocal three-dimensional uniaxial nematic liquid crystals in the presence of an externally applied bias voltage. We calculate fundamental soliton profiles by using the modified Petviashvili method under different boundary conditions (BCs). We obtain elliptical soliton profiles in rectangular samples. We study the influence of BCs on the fundamental solitons obtained. We report the existence of crystal thicknesses for which specific solitons from a given family of fundamental solitons achieve minimal power and maximal width.

Counterpropagating photorefractive spatial solitons

This study introduces a model for the interaction of counterpropagating spatial solitons using the photorefractive screening nonlinearity. To correctly describe the type of interaction considered, the model takes into account the spatial propagation of the light field as well as the temporal evolution of the screening space charge field. The model equations are evaluated numerically for incident beams with a varying degree of mutual coherence. Depending on the strength of the nonlinearity and the degree of coherence, as well as on the incident geometry, i.e. the lateral offset and the angle between both beams, a broad range of behavior is reported.

Generation and control of photorefractive soliton lattices

This study extends the experimental creation of arrays of parallel propagating solitons as first demonstrated previously to larger lattices and investigates potential control and waveguiding features. The dependence of mutual interaction on the separation of adjacent channels is studied in order to show the potential of these solitonic lattices for applications in telecommunications. This work also demonstrates waveguiding using red (/spl lambda/ = 633 nm) and infrared light ( /spl lambda/ = 1.55 /spl mu/m). In the latter case, a spatially resolved infrared-to-visible light converter using a gas discharge system is used. Moreover, this study shows induced control of solitons in these large lattices using coherent and incoherent steering beams.