Efficient generation and sorting of orbital angular momentum eigenmodes of light by thermally tuned q-plates

We present methods for generating and for sorting specific orbital angular momentum (OAM) eigenmodes of a light beam with high efficiency, using a liquid crystal birefringent plate with unit topological charge, known as \qo{q-plate}. The generation efficiency has been optimized by tuning the optical retardation of the q-plate with temperature. The measured OAM $m=\pm2$ eigenmodes generation efficiency from an input TEM$_{00}$ beam was of 97%. Mode sorting of the two input OAM $m=\pm2$ eigenmodes was achieved with an efficiency of 81% and an extinction-ratio (or cross-talk) larger than 4.5:1.Comment: 4 pages, 3 Figures and 1 table. Submitte

Quantized Rotation of Atoms From Photons with Orbital Angular Momentum

We demonstrate the coherent transfer of the orbital angular momentum of a photon to an atom in quantized units of hbar, using a 2-photon stimulated Raman process with Laguerre-Gaussian beams to generate an atomic vortex state in a Bose-Einstein condensate of sodium atoms. We show that the process is coherent by creating superpositions of different vortex states, where the relative phase between the states is determined by the relative phases of the optical fields. Furthermore, we create vortices of charge 2 by transferring to each atom the orbital angular momentum of two photons.Comment: New version, 4 pages and 3 figures, accepted for publication in Physical Review Letter

Modeling the fundamental characteristics and processes of the spacecraft functioning

The fundamental aspects of modeling of spacecraft characteristics by using computing means are considered. Particular attention is devoted to the design studies, the description of physical appearance of the spacecraft, and simulated modeling of spacecraft systems. The fundamental questions of organizing the on-the-ground spacecraft testing and the methods of mathematical modeling were presented

Realization of a semiconductor-based cavity soliton laser

The realization of a cavity soliton laser using a vertical-cavity surface-emitting semiconductor gain structure coupled to an external cavity with a frequency-selective element is reported. All-optical control of bistable solitonic emission states representing small microlasers is demonstrated by injection of an external beam. The control scheme is phase-insensitive and hence expected to be robust for all-optical processing applications. The motility of these structures is also demonstrated

Spin-to-Orbital Angular Momentum Conversion in Semiconductor Microcavities

We experimentally demonstrate a technique for the generation of optical beams carrying orbital angular momentum using a planar semiconductor microcavity. Despite being isotropic systems, the transverse electric - transverse magnetic (TE-TM) polarization splitting featured by semiconductor microcavities allows for the conversion of the circular polarization of an incoming laser beam into the orbital angular momentum of the transmitted light field. The process implies the formation of topological entities, a pair of optical half-vortices, in the intracavity field

The role of International trade in improving the competitiveness of Saint Petersburg

This article aims to explore the prospects for the development of international trade and the impact of trade on increasing competitiveness of Saint Petersburg. To this end, the authors study the theoretical aspects of regional competitiveness as such, analyse the ten years’ data on the city’s international trade, and explore the significance of image, reputation, and information support for the region’s international trade provided by business information centres abroad. The authors employ the methods of expert opinion and statistical analysis as well as the authors’ own data to consider the problems of international trade development in Saint Petersburg and the ways to improve the city’s competitiveness. The authors estimate the international trade performance of Saint Petersburg and outline the key areas for increasing the city’s competitive ability. This article has theoretical and practical significance for experts studying regional competitiveness, for regional authorities, and the business community

Formation of metallic magnetic clusters in a Kondo-lattice metal: Evidence from an optical study

Magnetic materials are usually divided into two classes: those with localised magnetic moments, and those with itinerant charge carriers. We present a comprehensive experimental (spectroscopic ellipsomerty) and theoretical study to demonstrate that these two types of magnetism do not only coexist but complement each other in the Kondo-lattice metal, Tb2PdSi3. In this material the itinerant charge carriers interact with large localised magnetic moments of Tb(4f) states, forming complex magnetic lattices at low temperatures, which we associate with self-organisation of magnetic clusters. The formation of magnetic clusters results in low-energy optical spectral weight shifts, which correspond to opening of the pseudogap in the conduction band of the itinerant charge carriers and development of the low- and high-spin intersite electronic transitions. This phenomenon, driven by self-trapping of electrons by magnetic fluctuations, could be common in correlated metals, including besides Kondo-lattice metals, Fe-based and cuprate superconductors.Comment: 30 pages, 6 Figure

Optical vortex generation from molecular chromophore arrays

The generation of light endowed with orbital angular momentum, frequently termed optical vortex light, is commonly achieved by passing a conventional beam through suitably constructed optical elements. This Letter shows that the necessary phase structure for vortex propagation can be directly produced through the creation of twisted light from the vacuum. The mechanism is based on optical emission from a family of chromophore nanoarrays that satisfy specific geometric and symmetry constraints. Each such array can support pairs of electronically delocalized doubly degenerate excitons whose azimuthal phase progression is responsible for the helical wave front of the emitted radiation. The exciton symmetry dictates the maximum magnitude of topological charge; detailed analysis secures the conditions necessary to deliver optical vortices of arbitrary order

Theoretical and methodological approaches to management of resource flow processes of development projects on macro-, mezzo-, microlevels

Paper is devoted to the actual problem of managing resource flows of development projects as complex, unique, and open systems, across the different project lifecycle stages that differ in content and are distributed in space and time. The idea was to create a single throughout system for managing resource flow processes of the long-term projects. The research goal included development of theoretical and methodological approaches that can be used in order to manage the combination of development project resource flows using "order from chaos"paradigm. That includes by-stage organization of resource flow processes on of macro-, meso- and microscale, going from sources and sinks of the chaotic project environment resolve to ordered stages of project life cycles. It is proposed to implement resource flow management in form of the stage and resource-based "project-logistic"relay of a triune movement, ordering and transformation of the resource flow processes. This relay is created within a project-logistic field of project management that change by project phases. Synergetic effects of self-organization and self-control appear in the project logistic field due to horizontal interactions, sharing experience, competences, and values among the stakeholders in course of transforming entropic resource-flow processes into the negentropy processes related to project phase goals (attractors). Results can be used to forecast and develop multilevel resource-flow and process systems arranged by resource sources and sinks, and chaotically ordered for projects in different application areas. Further research perspectives include development of self-control and self-organization forms for development projects stakeholders that would comply with international best practices, and fit corresponding project stages. © Published under licence by IOP Publishing Ltd

Pattern manipulation via on-chip phase modulation between orbital angular momentum beams

An integrated approach to thermal modulation of relative phase between two optical vortices with opposite chirality has been demonstrated on a silicon-on-insulator substrate. The device consists of a silicon-integrated optical vortex emitter and a phase controlled 3 dB coupler. The relative phase between two optical vortices can be actively modulated on chip by applying a voltage on the integrated heater. The phase shift is shown to be linearly proportional to applied electrical power, and the rotation angle of the interference pattern is observed to be inversely proportional to topological charge. This scheme can be used in lab-on-chip, communications and sensing applications. It can be intentionally implemented with other modulation elements to achieve more complicated applications