Twisted anisotropic fibers for robust orbital-angular-momentum-based information transmission

Abstract

We study the light propagation in the twisted anisotropic optical fibers endowed with torsional mechanical stress by obtaining the analytical solution o f the vector wave equation. We show that at certain interplay between fiber parameters optical vortex beams o f topological charge l = 0 ,± 1 ,± 2 ,... become the modes o f the fibers in question. To explain the splitting of the optical vortex propagation constants we introduce the notions of orbital birefringence and optical Zeeman effect. Moreover, we unveil that induced by torsional stress circular birefringence makes the vortex beams with the well-defined orbital angular momentum robust against small perturbations characterized by both constant and spatially varying orientation o f a director. We believe that such fibers can be successfully utilized for the long-range robust transmission of information encoded in the light's orbital degrees o f freedom.

Helically twisted photonic crystal fibres

“…The OAM birefringence displayed by twisted multicore PCFs is of interest in OAM-based optical communications [35,36] and may also be useful for flexible transmission of OAM in laser tweezer experiments for manipulation, for example, of cells.…”

“…Similar experiments carried out at multiple wavelengths and for fibre lengths up to 50 m confirmed that the twisted PCFs preserve the magnitude and sign of the OAM. The OAM birefringence displayed by twisted multicore PCFs is of interest in OAM-based optical communications [35,36] and may also be useful for flexible transmission of OAM in laser tweezer experiments for manipulation, for example, of cells.…”

Twist-induced guidance in coreless photonic crystal fiber: A helical channel for light

“…Twisted multicore PCFs have been shown to support helical Bloch waves and to exhibit orbital angular momentum (OAM) birefringence ( 9 ). There have also been many theoretical studies, for example, of spin-orbit coupling ( 10 , 11 ) and Bloch dynamics in helical coupled waveguide arrays ( 12 ). …”

Vortex Solitons in Twisted Circular Waveguide Arrays

“…Nevertheless, the impact of twisting on the properties and stability of self-sustained vortex states in the nonlinear regime has not been addressed, neither in ring-like arrays nor in rotating lattices, such as those described in [66][67][68][69][70][71]. Such rotating structures can be created using interfering nondiffracting beams [72,73] propagating in photosensitive materials [74][75][76], or as photonic crystal fibers twisted during drawing process [77][78][79]. The non-degeneracy of linear vortex modes with opposite charges occurs in linear twisted photonic crystal fibers [80] and is suggested by the excitations in optically-induced structures [76], but it has not been addressed directly in the nonlinear regime.…”