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Simferopol', Ukraine

Alexeyev C.N.,Taurida National University
Applied Optics | Year: 2012

We have theoretically studied long-period spun l-helicoidal fibers and their ability to generate singular beams from regular ones. On the basis of perturbation theory in the presence of degeneracy, applied to the scalar waveguide equation, we obtained the structure of coupled modes of such fibers and their spectra. It is shown that the coupled modes consist of the fields, which taken separately bear topological charges that differby l units. We have numerically studied the process of the passage of a Gaussian beam through such a fiber and demonstrated that long-period l-helicoidal fibers have the ability to change - in a certain wavelength range - the topological charge of the incoming Gaussian beam by l units, generating in this way charge-l optical vortex. © 2012 Optical Society of America. Source


Alexeyev C.N.,Taurida National University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

In this paper, we have studied the propagation of light in a p array, that is, a circular array of strongly anisotropic fibers, orientation of whose anisotropy axes linearly depends on the angular position of the fiber in the array and makes an integer number of full rotations p while tracing along its contour. We have obtained the spectrum and the structure of supermodes for such a system and have shown that they consist of two discrete optical vortices nestled in the opposite circular polarizations. We have found the expressions for topological charges of such vortices. We have also studied the angular momentum carried by these supermodes. We have obtained the expression for the evolution of an arbitrary excitation created at the array's input upon its discrete diffraction in the array. As an example, we have examined the propagation of the set of circularly polarized fundamental modes excited at the input end with equal weights and phases. We have demonstrated that, in certain cross sections, the p array generates a discrete circularly polarized optical vortex, whose topological charge is determined by the array's index p. In this way, we have shown that the p arrays enable polarization control over phase singularities being a discrete analog of the q plates. © 2012 American Physical Society. Source


Alexeyev C.N.,Taurida National University
Applied Optics | Year: 2013

We have studied theoretically reflecting and transmitting properties of Bragg multihelicoidal spun fibers, in which refractive index distribution features l helical branches and possesses an l-fold symmetry in the transverse cross section. It is shown that for a special choice of the profile function modulation, such fibers in certain spectral ranges have the property to change the topological charge of the incoming Gaussian beam in the reflected field by l units. This property could be used for narrowband generation of optical vortices (OVs) from Gaussian beams and for changing the topological charge of incoming OVs. © 2013 Optical Society of America. Source


Volyar Alexander V.,Taurida National University
Ukrainian Journal of Physical Optics | Year: 2013

We have considered a new type of singular beams called as optical quarks. They have fractional topological charges being equal to half an integer and they possess rather unique properties. There are four types of optical quarks, even and odd ones, which reveal the opposite signs of topological charges. The sums or differences of the even and odd quarks form standard vortex or non-vortex beams with the topological charges of integer order. All the quarks in the same beam annihilate and the beam vanishes. The analysis of angular spectra of the optical quarks shows that the latter represent structurally unstable forms of field under condition of free-space propagation. We have analysed their propagation properties for different types of beam envelope, including a symmetric beam array with discrete optical quarks. We have discussed the properties of possible structurally stable forms of the quarks and the media capable of maintaining the optical quarks. Source


Grant
Agency: Cordis | Branch: FP7 | Program: CP-SICA | Phase: ENV.2008.4.1.4.1. | Award Amount: 8.01M | Year: 2009

The Black Sea Catchment is internationally known as one of ecologically unsustainable development and inadequate resource management, which has led to severe environmental, social and economic problems. EnviroGRIDS @ Black Sea Catchment aims at building the capacities of regional stakeholders to use new international standards to gather, store, distribute, analyze, visualize and disseminate crucial information on past, present and future states of the environment, in order to assess its sustainability and vulnerability. The EnviroGRIDS @ Black Sea Catchment project addresses these issues by bringing several emerging information technologies that are revolutionizing the way we are able to observe our planet. The Group on Earth Observation Systems of Systems (GEOSS) is building a data-driven view of our planet that feeds into models and scenarios. EnviroGRIDS aims at building the capacity of scientist to assemble such a system in the Black Sea Catchment, the capacity of decision-makers to use it, and the capacity of the general public to understand the important environmental, social and economic issues at stake. To achieve its objectives, EnviroGRIDS will build an ultra-modern Grid enabled Spatial Data Infrastructure (GSDI) that will become one component in the Global Earth Observation System of Systems (GEOSS), compatible with the new EU directive on Infrastructure for Spatial Information in the European Union (INSPIRE). EnviroGRIDS will particularly target the needs of the Black Sea Commission (BSC) and the International Commission for the Protection of the Danube River (ICPDR) in order to help bridging the gap between science and policy.

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