Abstract
Two-dimensional optical vortex beams can propagate stably and undergo bending in nonlocal media with the aid of a spatial soliton, the latter preventing their destabilization and breakup. By colaunching a suitable pair of collinear soliton and vortex beams in nematic liquid crystals, we conduct a series of numerical experiments to demonstrate that the vortex beam can be made to propagate in the nematicon waveguide and follow its trajectory, even in the cases of refraction and total internal reflection at a dielectric interface. Modulation theory supports these findings and provides an excellent theoretical framework.
Highlights
Finite light beams are subject to diffraction unless the latter is balanced by additional linear or nonlinear effects, e.g. by spatial dispersion or self-focusing or gain guiding [1,2,3,4]
At variance withsombrero’’ refractive potentials, such as in antiguides [18], a bright soliton induces a dielectric waveguide and can, in some cases, confine and route a complex wavepacket such as a vortex. In this Paper we investigate collinear soliton-vortex pairs interacting with a dielectric interface and undergoing angular deviation by either refraction or total internal reflection
We investigate the evolution of nematicon-vortex wavepackets upon refraction/Total Internal Reflection (TIR) using both numerical solutions of the governing equations (1)-(3) and approximate evolution equations derived from modulation theory [49]
Summary
Finite light beams are subject to diffraction unless the latter is balanced by additional linear or nonlinear effects, e.g. by spatial dispersion or self-focusing or gain guiding [1,2,3,4]. With specific reference to nematic liquid crystals, but without loss of generality, we address the stabilization and guidance of vortex beams by means of nonlocal bright spatial solitons, using modulation theory for and numerical solutions of the equations governing the nonlinear, nonlocal response of reorientational media. U and v are the complex envelopes of the electric fields of the soliton (nematicon [9]) and vortex beams, respectively; F(x,z) indicates a y- uniform refractive index variation across the cell; the parameter Γ measures the elastic response of the medium and in the usual experimental regimes is large, 0(100) [9,33,34]; the parameter q is proportional to the magnitude of the external pre-tilting voltage (bias). Taking variations of the averaged Lagrangian (10) with respect to the nematicon and vortex parameters results in the variational, or modulation [49], equations ( ) d dz
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