Partial Wave Decomposition for Meson Exchange Currents in Few-Nucleon Systems

We develop an approach for calculating matrix elements of meson exchange currents between 3N basis states in (jJ)-coupling and a 3N bound state. The contribution generated by $\pi$- and $\rho$-exchange are included in the consideration. The matrix elements are expressed in terms of multiple integrals in the momentum space. We apply a technique of the partial wave decompositions and carry out some angular integrations in closed form. Different representations appropriate for numerical calculations are derived for the matrix elements of interest. The momentum dependences of the matrix elements are studied and benchmark results are presented. The approach developed is of interest for the investigations of deuteron- proton radiative capture and ^3He photo- and electrodisintegration when the interaction in the initial or final nuclear states is taken into account by solving the Faddeev equations.Comment: 32pages (14 figures

Subwavelength micropolarizer in a gold film for visible light

Engineering and Physical Sciences Research Council (EPSRC) (EP/L017008/1); European Research Council (337508); Russian Foundation for Basic Research (RFBR) (14-07-97039, 14-29-07133, 15-07-01174, 15-37-20723, 16-07-00990, 16-29-11698); Ministry of Education and Science of the Russian Federation (MK-9019.2016.2).We have designed and fabricated a 100 μm x 100 μm four-sector binary subwavelength reflecting polarization microconverter in a gold film. Using finite-difference time-domain-aided numerical simulations and experiments, the micropolarizer was shown to convert an incident linearly polarized Gaussian beam of wavelength 532 nm into an azimuthally polarized beam. Conditions for generating on-axis regions of nonzero intensity when using propagating optical vortices with different initial polarization were deduced. By putting a spiral phase plate into an azimuthally polarized beam, the intensity pattern was shown to change from diffraction rings to a central peak.PostprintPeer reviewe

Robust Multi-Partite Multi-Level Quantum Protocols

We present a tripartite three-level state that allows a secret sharing protocol among the three parties, or a quantum key distribution protocol between any two parties. The state used in this scheme contains entanglement even after one system is traced out. We show how to utilize this residual entanglement for quantum key distribution purposes, and propose a realization of the scheme using entanglement of orbital angular momentum states of photons.Comment: 9 pages, 2 figure

Local vibrations in real crystals with combined defects

The conditions of formation and the main characteristics of local vibrations due to the presence of light impurities Al, Mg, and Mn in the bulk and on the close-packed [111] surface of the fcc crystal lattice of silver are investigated. The influence of surface roughness is analyzed. Analytical approximations are obtained which describe the frequency and intensity of the local vibrations at the impurity atom and its nearest neighborhood to high accuracy. The proposed analytical approximations provide a practical way of determining the parameters of the defect structure and the interatomic interactions from the experimentally determined characteristics of the local vibrations

Spin structure of three-nucleon bound states

The spin-dependent momentum distributions (SDMDs) of nucleons and proton-deuteron clusters in polarized ³He and ³H nuclei are studied with wave functions (WFs) for realistic models of nuclear forces.Хвильові функції для реалістичних моделей ядерних сил використовуються для дослідження залежних від спина імпульсних розподілів нуклонів і нуклон-дейтронних кластерів у поляризованих ядрах ³He та ³H.Волновые функции для реалистических моделей ядерных сил используются для исследования зависящих от спина импульсных распределений нуклонов и нуклон-дейтронных кластеров в поляризованных ядрах ³He и ³H

Tight focusing of laser light using a chromium Fresnel zone plate

Funding: Russian Scientific Foundation (17-19-01186).Using near-field scanning microscopy, we demonstrate that a 15-µm zone plate fabricated in a 70-nm chromium film sputtered on a glass substrate and having a focal length and outermost zone's width equal to the incident wavelength λ = 532 nm, focuses a circularly polarized Gaussian beam into a circular subwavelength focal spot whose diameter at the full-width of half-maximum intensity is FWHM = 0.47λ. This value is in near-accurate agreement with the FDTD-aided numerical estimate of FWHM = 0.46λ. When focusing a Gaussian beam linearly polarized along the y-axis, an elliptic subwavelength focal spot is experimentally found to measure FWHMx = 0.42λ (estimated value FWHMx = 0.40λ) and FWHMy = 0.64λ. The subwavelength focal spots presented here are the tightest among all attained so far for homogeneously polarized beams by use of non-immersion amplitude zone plates.PostprintPeer reviewe

Subwavelength gratings for polarization conversion and focusing of laser light

We review thin micro-optics components with nanostructured microreliefs intended to control the polarization and phase of laser light. These components include transmission and reflection subwavelength diffraction gratings characterized by spatially −varying groove directions and fill factors, with the microrelief period and depth remaining approximately unchanged. In the visible spectrum, the microrelief features may vary in size from dozens to hundreds of nanometers. Segmented diffractive micropolarizers for linear to radial/azimuthal polarization conversion and subwavelength microlenses for tightly focusing the laser light are discussed in detail. Examples of particular micropolarizers and microlenses fabricated in amorphous silicon films are also given

Microlens-aided focusing of linearly and azimuthally polarized laser light

Funding: Russian Foundation for Basic Research (RFBR) (14-29-07133, 14-07-97039, 15-07-01174, 15-47-02492, 15-37-20723, 16-07-00990, 16-47-630483); Ministry of Education and Science of the Russian Federation (NSh-4128.2016.9, MK-9019.2016.2); European Research Council (337508).We have investigated a four-Sector transmission Polarization Converter (4-SPC) for a wavelength of 633 nm, that enables the conversion of a linearly polarized incident beam into a mixture of linearly and azimuthally polarized beams. It was numerically shown that by placing a Fresnel zone plate of focal length 532 nm immediately after the 4-SPC, the incident light can be focused into an oblong subwavelength focal spot whose size is smaller than the diffraction limit (with width and breadth, respectively, measuring FWHM = 0.28λ and FWHM = 0.45λ, where λ is the incident wavelength and FWHM stands for full-width at half maximum of the intensity). After passing through the 4-SPC, light propagates in free space over a distance of 300 μm before being focused by a Fresnel zone plate (ZP), resulting in focal spot measuring 0.42λ and 0.81λ. The focal spot was measured by a near-field microscope SNOM, and the transverse E-field component of the focal spot was calculated to be 0.42λ and 0.59λ. This numerical result was verified experimentally, giving a focal spot of smaller and larger size, respectively, measuring 0.46λ and 0.57λ. To our knowledge, this is the first implementation of polarization conversion and subwavelength focusing of light using a pair of transmission micro-optic elements.PostprintPeer reviewe