We demonstrate that in-bulk vortex localized modes, and their surface half-vortex (“horseshoe”) counterparts (which were not reported before in truncated settings) self-trap in two-dimensional (2D) nonlinear optical systems with PT-symmetric photonic lattices (PLs). The respective stability regions are identified in the underlying parameter space. The in-bulk states are related to truncated nonlinear Bloch waves in gaps of the PL-induced spectrum. The basic vortex and horseshoe modes are built, severally, of four and three beams with appropriate phase shifts between them. Their stable complex counterparts, built of up to 12 beams, are reported too.

http://arxiv.org/abs/1403.4745
Optics (physics.optics); Pattern Formation and Solitons (nlin.PS)

We investigate light beam propagation along the interface between linear and nonlinear media with parity-time PT symmetry, and derive an equation governing the beam propagation. A novel class of two-dimensional PT surface solitons are found analytically and numerically, and checked to be stable over a wide range of PT potential structures and parameters. These surface solitons do not require a power threshold. The transverse power flow across beam is examined within the solitons and found to be caused by the nontrivial phase structure of the solitons. PT surface solitons are possibly observed experimentally in photorefractive crystals.

http://arxiv.org/abs/1304.6788
Optics (physics.optics); Pattern Formation and Solitons (nlin.PS)

We study effects of the spontaneous symmetry-breaking (SSB) in solitons built of the dipolar Bose-Einstein condensate (BEC), trapped in a dual-core system with the dipole-dipole interactions (DDIs) and hopping between the cores. Two realizations of such a matter-wave coupler are introduced, weakly- and strongly-coupled. The former one in based on two parallel pipe-shaped traps, while the latter one is represented by a single pipe sliced by an external field into parallel layers. The dipoles are oriented along axes of the pipes. In these systems, the dual-core solitons feature the SSB of the supercritical type and subcritical types, respectively. Stability regions are identified for symmetric and asymmetric solitons, and, in addition, for non-bifurcating antisymmetric ones, as well as for symmetric flat states, which may also be stable in the strongly-coupled system, due to competition between the attractive and repulsive intra- and inter-core DDIs. Effects of the contact interactions are considered too. Collisions between moving asymmetric solitons in the weakly-symmetric system feature elastic rebound, merger into a single breather, and passage accompanied by excitation of intrinsic vibrations of the solitons, for small, intermediate, and large collision velocities, respectively. A PT-symmetric version of the weakly-coupled system is briefly considered too, which may be relevant for matter-wave lasers. Stability boundaries for PT-symmetric and antisymmetric solitons are identified.

http://arxiv.org/abs/1212.5568

Quantum Gases (cond-mat.quant-gas); Pattern Formation and Solitons (nlin.PS)

It is studied the bright spatial solitons in nonlocal defocusing Kerr media with parity-time (PT) symmetric potentials. We find that these solitons can exist and be stable over a different range of potential parameters. The influence of the degree of nonlocality on the solitons and the transverse energy flow within the stable solitons are also examined.

http://arxiv.org/abs/1110.5108
Optics (physics.optics)