We investigate the propagation of optical vortices in strongly elliptic weakly guiding fibres. A novel method of the perturbation theory developing is suggested based on the simple change of variables that effectively makes it possible to take account of the field amplitude corrections in higher orders of perturbation theory. The form of a generic elliptic vortex in elliptic fibres is found to be a mixture of partial circular vortices.
We investigate the influence of the spin-orbit coupling on the band-gap structure in a weakly guiding strongly anisotropic
optical fiber, in which the anisotropy axis uniformly rotates in a transverse plane with z increasing. It is demonstrated
that the spin-orbit coupling slightly renormalizes the spectrum gap. The structure of modes in the gap vicinity is also
slightly renormalized by this coupling.
In the article we consider some manifestations of the rotational Doppler effect in weakly guiding optical fibers. The fiber
chosen as a sample has a waveguide parameter V<3.8 that corresponds to eigen modes with azimuth indices l=0,1
realizing in the fiber. We showed the polarizer rotation in the radiation field to come to rotating an intensity zero. A zero
trajectory and rotation frequency depends on excitation conditions, a fiber length and an initial polarization state.
We investigate polarization state evolution in the fundamental mode in a weakly guiding highly elliptic twisted optical fiber. On the basis of the scalar wave equation the analytical expression for the fundamental mode is obtained. Twisting-induced polarization corrections to the propagation constant are found. It is demonstrated that in some limiting case the rise of such corrections can be explained as a manifestation of topological Pancharatnam-Berry's phase.
We investigate the band-gap structure in a weakly guiding strongly anisotropic optical fiber, in which the anisotropy axis uniformly rotates in a transverse plane with z increasing. It is demonstrated that there is a gap in the spectrum of the scalar wave equation with the width proportional to the anisotropy constant.
We investigate the mode structure of a weakly guiding anisotropic optical fiber, in which the anisotropy axis rotates in a transverse plane with z increasing. It is demonstrated that at certain values of the anisotropy pitch the spin-orbit coupling is in effect damped and 1=1 modes of the fibers are almost pure linear optical vortices. Polarization corrections to the propagation constant are found. It is demonstrated that in some limiting cases the rise of such corrections can be explained as a manifestation of topological Pancharatnam-Berry’s phase.
The combined singular beams generated by saddle-like imperfections of the cover glass surface in IR spectral range is subjected to the unfolding process near the focal plane of a microobjective. As far as such beams have their intensity profile similar to those of the optical vortices with the quaternary topological charge they can be exploited for the trapping and transportation of large micro particles. In contrast to the ordinary high-order optical vortices being unstable against the slight perturbations of the beam's shape, the given singular beams conserve their topological structure to trap and carry over the particles up to 200 μm in sizes. This fact is discussed in detail in the given work.
The mode structure in weakly guiding twisted fibers is investigated. It is demonstrated that in the case of small pitch of twist in the model without the spin-orbit coupling modes of twisted fibers are almost pure circular vortices with suppressed mode dispersion. The influence of the spin- orbit coupling on mode structure in twisted fibers is discussed.
A mechanical bent of an optical fiber induces perturbations of geometrical and material fiber parameters. Due to these factors there arise both wave field distortions and variations of a mode propagation constant. In the given paper, polarization corrections to propagation constants are shown to be mean values of the spin-orbit operator of a singular beam in a bent optical fiber. The propagation process of eigen modes in those fibers is analyzed.
Properties of vortical fields in an elliptic weakly guiding optical fiber are considered. The eigenfunctions and the spectrum of polarization corrections to the scalar propagation constant in the case of relatively large and small values of a fiber ellipticity are obtained by means of the spin-orbit interaction operator method. It is discussed the conversion process of a spin and orbit angular momenta on a vortex propagation.
On the basis of spin continuity equation we study the propagation of light in locally isotropic inhomogeneous media. We have obtained refined value of linear birefringence of order ((lambda) /(alpha) )2 in layered media. We have studied spin transformations in perturbed weakly guiding fibers and proved that spin dynamics in fibers is governed by Heisenberg equation for a spin-1/2 particle.
Macroscopic continuity equation for the angular momentum (AM) of radiation, valid in arbitrary media, is built. The expression for sources of the AM are obtained. On the basis of the equation the stability of the total AM flux in round weakly guiding optical fibers with elliptically deformed section is investigated. The conservation of the total AM flux of the circular optical vortex in the first order in deformation is demonstrated. On the basis of the equation an approximate expression for the torque acting on an absorbing particle in arbitrary electromagnetic field is obtained. The comparison with the know results is carried out.
Macroscopic continuity equation for spin momentum of radiation in vacuum is obtained. On the basis of continuity equations for spin and angular momentum (AM) the refined description of the classical R.A. Beth's experiment (that is with the of reflections on both the faces of the plate) is developed. It is demonstrated that a quarter-wavelength plate transforms a spin flux--0 radiation field into a spin flux--1 one. The effect of nonmonochromaticity of the incident beam is studied. The passage of beams with their own AM and finite lateral extent through a quarter-wave plate is considered.
An orbital angular momentum of a circular vortex in a low-mode fiber is studied. An experimental scheme based on a mechanism of a total reflection is proposed. The expression of mechanical torque induced by radiation is obtained.
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