38 research outputs found
Rate coefficients of exchange reactions accounting for vibrational excitation of reagents and products
No full textEffect of dipole orientation on Purcell factor for the quantum emitter near silicon nanoparticle
No full textCampsites of the Southern Urals Nomads in the Middle of the I Millennium BC (according to data from the Bannoye – Sabakty – Karabalykty Lake System)
No full textThe 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
On the Southern Border of the Forest and Forest-Steppe Cultures in the Urals in the Ist Millennium BC
No full textThe article demonstrates that the central part of South Ural Mountains with surrounding foot-hills was a special transzonal territory, where the natural conditions prevented development of homogenous and stable ethnic and cultural formations in the central part of the South-Ural region. In the I Millennium BC, this region accepted numerous groups of forest and northern forest-steppe population who continuously migrated here from the north and lived in the immediate vicinity to the steppe nomads. The author identified three main itineraries of such groups migrating to the south. A number of laws of interaction of forest and northern forest-steppe early Iron Age population was considered, both among themselves and with the nomads
Topological states in arrays of optical waveguides engineered via mode interference
No full textPhotonic structures with topologically nontrivial bands are usually designed by arranging simple meta-atoms, ideally, single-mode ones, in a carefully designed photonic lattice with symmetry that guarantees the emergence of topological states. Here we investigate an alternative option that does not require complex lattice geometry but instead relies on the tuning of the parameters of the individual meta-atoms to achieve the degeneracy of the modes with different symmetry. As an illustrative example, we consider a one-dimensional array of equidistant identical periodic nanophotonic waveguides supporting degenerate modes with strongly asymmetric near field profiles giving rise to the coupling modulation. Exploiting this feature, we demonstrate that the proposed system supports topological edge modes and can be viewed as a generalization of the paradigmatic Su-Schrieffer-Heeger model, reducing to it for the suitable parameter choice. Our results thus provide an avenue to engineer topological states via mode interference which further expands the plethora of topological structures available in photonics being especially promising for nonlinear topological systems
Unidirectional coupling of a quantum emitter to a subwavelength grating waveguide with engineered stationary inflection point
No full textIn this work, we propose an approach for the design of a waveguide structure that allows for efficient and highly asymmetric coupling of the quantum sources with circularly polarized transition dipole moments to the guided mode of the structure. The approach is based on the mixing of the two quasi-degenerate modes of a periodic waveguide with an auxiliary single-mode waveguide leading to the formation of the dispersion with a stationary inflection point and consequently to the high coupling efficiency of this mode with a dipole source. We show that the distribution of the field polarization inside the waveguide is relatively homogeneous maintaining the circular polarization in a large area. Consequently, this leads to a high degree of tolerance of the coupling asymmetry and strength to the position of the quantum emitter. We believe, that our results will extend the variety of designs of the efficient chiral nanophotonic interfaces based on planar semiconductor nanostructures
Ultrafast Tunable Hybrid Yagi-Uda Nanoantenna
No full textWe study radiation from Yagi-Uda nanoantennas composed of metal-dielectric core-shell nanoparticles. We have found an interesting operation regime in such nanoantennas determined by their hybrid nature. This regime rests on the excitation of the Van Hove singularity, supporting high values of directivity and Purcell factor within the same narrow frequency range. In this regime, a strong dynamical tuning of the emission pattern via electron-hole plasma photoexcitation by a femtosecond pumping can be achieved
HighQ Localized States in Finite Arrays of Subwavelength Resonators
No full textWe
uncover how to achieve giant Q-factors in finite-length
periodic arrays of subwavelength optical resonators. The underlying
physics is based on interference between the band-edge mode and a
standing mode in the array, and it leads to the formation of spatially
localized states with dramatically suppressed radiative losses. We
demonstrate this concept for an array of N dipoles
with simultaneous cancellation of multipoles up to N-th order and the Q-factor growing as Q ∝ Nα, where α ≳
6.88. We study a realistic array of nanoparticles (N ≲ 37) supporting the magnetic dipole Mie resonances with
the enhanced Purcell factor (∼7600) achieved by tuning the
array parameters
Solitary Waves in Chains of High-Index Dielectric Nanoparticles
No full textWe study both linear
and nonlinear propagation of pulses in waveguides
composed of high-index dielectric nanoparticles supporting both electric
and magnetic resonances. We reveal that short pulses (∼100
fs) broaden significantly in the linear regime after propagating only
several tens of micrometers, due to a strong waveguide dispersion.
In the nonlinear regime, the pulses propagating in the chains of spherical
nanoparticles broaden even more strongly than in the linear regime
due to defocusing nonlinearity. However, for the chains of nanodisks
the pulse broadening can be compensated by the nonlinear effect, due
to the interplay of the electric and magnetic resonances that can
change the sign of the group-velocity dispersion for some frequencies,
making possible the formation and propagation of solitary waves and
effective generation of the new frequencies. Our results demonstrate
that considered systems can serve as a promising platform for nonlinear
and ultrafast nanophotonics, allowing the observation of strong nonlinear
effects at the micrometer scales
