115 research outputs found
Campsites of the Southern Urals Nomads in the Middle of the I Millennium BC (according to data from the Bannoye – Sabakty – Karabalykty Lake System)
The paper deals with the materials from three sites, namely the settlement Bannoye-5a (Berezki), Telyashevo-4 and Sabakty-3/5. They are discovered with ceramics of the early nomads (late V – late IV century BC). All these sites are situated within a narrow strip of mountain steppes along the eastern slope of the Southern Urals (modern Abzelilovsky district of the Republic of Bashkortostan). It is on the same latitude as Magnitogorsk. The settlement Bannoye-5a (Berezki) was studied in 1972–1976 and 2004–2005. The received materials were analyzed and showed three points of spread early nomadic ceramics. Two of them were revealed by excavations and are rather small in size. Also a similar situation was at Telyashevo-4 settlement. It is shown that all three sites can be interpreted as nomadic campsites. When the author analyzes all the information about the spread area of Southern Ural nomads in the middle of the I millennium BC, the author can conclude that the campsites and other types of settlements close to them were quite common (more than 30 sites are currently recorded). It is particularly complicated to find and register such kind of sites, however, studying them is the only way to learn something new about their household, spread and land development
Coherent control of topological states in an integrated waveguide lattice
Topological photonics holds the promise for enhanced robustness of light
localization and propagation enabled by the global symmetries of the system.
While traditional designs of topological structures rely on lattice symmetries,
there is an alternative strategy based on accidentally degenerate modes of the
individual meta-atoms. Using this concept, we experimentally realize
topological edge state in an integrated optical nanostructure based on the
array of silicon nano-waveguides, each hosting a pair of degenerate modes at
telecom wavelengths. Exploiting the hybrid nature of the topological mode
formed by the superposition of waveguide modes with different symmetry, we
implement coherent control of the topological edge state by adjusting the phase
between the degenerate modes and demonstrating selective excitation of bulk or
edge states. The resulting field distribution is imaged via third harmonic
generation allowing us to quantify the localization of topological modes as a
function of the relative phase of the excitations. Our results highlight the
impact of engineered accidental degeneracies on the formation of topological
phases, extending the opportunities stemming from topological nanophotonic
systems.Comment: 17 pages, 4 figure
Laser-driven pointed acceleration of electrons with preformed plasma lens
The simultaneous laser-driven acceleration and angular manipulation of the
fast electron beam is experimentally demonstrated. The bunch of multi-MeV
energy charged particles is generated during the propagation of the femtosecond
laser pulse through the near-critical plasma slab accompanied by plasma
channeling. Plasma is formed by the controlled breakdown of a thin-tape target
by a powerful nanosecond prepulse. The electron beam pointing approach is based
on the refraction of a laser pulse in the presence of a strong radial density
gradient in the breakdown of the tape with a small displacement of the
femtosecond laser beam relative to the breakdown symmetry axis. A shift of
several micrometers makes it possible to achieve beam deflection by an angle up
to 10 degrees with acceptable beam charge and spectrum conservation. This opens
up opportunities for in-situ applications for scanning objects with an electron
beam and the multistage electron beam energy gain in consecutive laser
accelerators without bulk magnetic optics for particles. Experimental findings
are supported by numerical Particle-In-Cell calculations of laser-plasma
acceleration and hydrodynamic simulations.Comment: Submitted to PPC
Bending of electromagnetic waves in all-dielectric particle array waveguides
We propose and demonstrate experimentally an alternative approach for realizing subwavelength photonic structures, exploiting the waveguiding properties of chains of high-index dielectric disks with both electric and magnetic dipole resonances. We reveal that the electromagnetic energy can be efficiently guided through sharp corners by means of the mode polarization conversion at waveguide bends. We confirm experimentally the guidance through a 90° bend in the microwave frequency range.This work was supported by the Ministry of Education
and Science of the Russian Federation (Project
11.G34.31.0020, GOSZADANIE 2014/190, Zadanie No.
3.561.2014/K, 14.584.21.0009 10), by Russian Foundation
for Basic Research, the Dynasty Foundation (Russia), the
Australian Research Council via Future Fellowship Program
(No. FT110100037), and the Australian National University
All-Optical Switching and Unidirectional Plasmon Launching with Nonlinear Dielectric Nanoantennas
High-index dielectric nanoparticles have become a powerful platform for nonlinear nanophotonics due to special types of optical nonlinearity, e.g. caused by electron-hole plasma (EHP) photoexcitation. We propose a highly tunable dielectric nanoantenna consisting of a chain of silicon particles excited by a dipole emitter. The nanoantenna exhibits slow group-velocity guided modes, corresponding to the Van Hove singularity in an infinite structure, which enable a large Purcell factor up to several hundred and are very sensitive to the nanoparticle permittivity. This sensitivity enables the nanoantenna tuning via EHP excitation with an ultrafast laser pumping. Dramatic variations in the nanoantenna radiation patterns and Purcell factor caused by ultrafast laser pumping of several boundary nanoparticles with relatively low intensities of about 25 GW/cm2 are shown. Unidirectional surface-plasmon polaritons launching with EHP excitation in the nanoantenna on a Ag substrate is demonstrated
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