Optical switching and logic gates with hybrid plasmonic-photonic crystal nanobeam cavities

We propose a hybrid resonance architecture in which a plasmonic element is coupled to a silicon-on-insulator photonic crystal nanobeam cavity operating at telecom wavelengths. It benefits from the combined characteristics of the photonic cavity and the plasmonic element, and exploits the unique properties of Fano resonances resulting from interactions between the continuum and the localized cavity states. As confirmed through 3D time-domain simulations, a strong cavity mode damping by the plasmonic element offers mechanisms of controlling a probe signal propagating in the nanobeam. It makes possible to create optical switching devices and logic gates relying on any optical nonlinear effect.     

Artifact Reduction Based on Sinogram Interpolation for the 3D Reconstruction of Nanoparticles Using Electron Tomography

Electron tomography is a well‐known technique providing a 3D characterization of the morphology and chemical composition of nanoparticles. However, several reasons hamper the acquisition of tilt series with a large number of projection images, which deteriorate the quality of the 3D reconstruction. Here, an inpainting method that is based on sinogram interpolation is proposed, which enables one to reduce artifacts in the reconstruction related to a limited tilt series of projection images. The advantages of the approach will be demonstrated for the 3D characterization of nanoparticles using phantoms and several case studies.     

Shallow Donors and Deep-Level Color Centers in Bulk AlN Crystals: EPR, ENDOR, ODMR and Optical Studies

The results of studies of shallow donors and deep-level color centers in bulk AlN crystals are presented. Two shallow donors (presumably oxygen located on the nitrogen site and carbon located on the aluminum site) are suggested to exhibit the DX-relaxation. Third shallow donor (presumably silicon on the Al site) shows the shallow donor behavior up to the room temperature and can be observed without light excitation at temperatures above 200 K. The values of the Bohr radius of the shallow donors are estimated. The structure of deep-level color centers (neutral nitrogen vacancy V _N) in bulk AlN crystals is determined and analyzed by electron paramagnetic resonance, electron-nuclear double resonance, optical absorption and thermoluminescence induced by X-ray irradiation. Spin-dependent recombination processes in AlN crystals are studied by means of optically detected magnetic resonance.     

Kinematics in matrix gravity

We develop the kinematics in Matrix Gravity, which is a modified theory of gravity obtained by a non-commutative deformation of General Relativity. In this model the usual interpretation of gravity as Riemannian geometry is replaced by a new kind of geometry, which is equivalent to a collection of Finsler geometries with several Finsler metrics depending both on the position and on the velocity. As a result the Riemannian geodesic flow is replaced by a collection of Finsler flows. This naturally leads to a model in which a particle is described by several mass parameters. If these mass parameters are different then the equivalence principle is violated. In the non-relativistic limit this also leads to corrections to the Newton’s gravitational potential. We find the first and second order corrections to the usual Riemannian geodesic flow and evaluate the anomalous nongeodesic acceleration in a particular case of static spherically symmetric background.     

Succession of one-soliton pulses in the zero-dispersion region of silica optical fibres: The role of the phase difference between the adjacent pulses

Some features of the propagation of one-soliton successions in the third order dispersion region are presented for the case where the phase difference between adjacent pulses is rads. We show that this considerably improves the stability of the pulses in the zero-dispersion region. Walk-off can be diminished by increasing the number of pulses in the succession. These features may help optimize the bandwidth of non-linear fibre communication links.     

Electrical conductivity in very anisotropic conductors and semiconductors

Summary For very anisotropic metallic and semiconducting systems it is shown that the electrical conductivity in the direction of high effective mass decreases as the number of electrons in the conduction band grows. In the other directions the conductivity behaves normally.

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Riassunto Si mostra che, per sistemi semiconduttori e metallici anisotropi, la conduttività elettrica nella direzione di massa altamente efficace diminuisce all'aumentare del numero di elettroni nella banda di conduzione. Nelle altre direzioni la conduttività si comporta normalmente.

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Резюме Для очень анизотропных металлических и полупроводниковых систем показывается, что электропропроводность в направлении большой эффективной массы уменьшается, когда число электронов в зоне проводимости увеличивается. В других направлениях проводимость ведет себя нормальным образом.

     

Buckling-driven morphological transformation of droplets of a mixed colloidal suspension during evaporation-induced self-assembly by spray drying

Morphological transformation during evaporation-induced self-assembly of a mixed colloidal suspension in micrometric droplets has been investigated. It has been demonstrated that a buckling-driven shape transition of drying droplets of mixed colloidal suspension takes place during evaporation-induced self-assembly. Further, it is also shown that the distortion modulations get significantly amplified with enhancement in volume fraction of anisotropic soft colloidal component of the mixed colloids. It has been argued that the reduction in elastic modulus of formed shell, at the boundary of a drying droplet, and the anisotropic nature of one of the colloidal components facilitate the deformation process. Hierarchical structures of these assembled colloidal grains have been probed using electron microscopy and scattering techniques.     

Spinless Duffin-Kemmer-Petiau Oscillator in a Galilean Non-commutative Phase Space

We examine Galilei-invariant linear wave equations in a non-commutative phase space. Specifically, we establish and solve the Galilean covariant Duffin-Kemmer-Petiau equation for spin-0 fields in a harmonic oscillator potential. We obtain these wave equations with a Galilean covariant approach, based on a (4+1)-dimensional manifold with light-cone coordinates followed by a reduction to a (3+1)-dimensional spacetime. We find the exact wave functions and their energy levels, and we examine the effects of non-commutativity.     

Preservation of the Pt(100) surface reconstruction after growth of a continuous layer of graphene

Scanning tunneling microscopy shows that a layer of graphene can be grown on the hex-reconstructed Pt(100) surface and that the reconstruction is preserved after growth. A continuous sheet of graphene can be grown across domain boundaries and step edges without loss of periodicity or change in direction. Density functional theory calculations on a simple model system support the observation that the graphene can have different rotation angles relative to the hex-reconstructed Pt surface. The graphene sheet direction can be changed by incorporating pentagon-heptagon defects giving rise to accommodation of edge dislocations. The defect formation energy and the induced buckling of the graphene have been characterized by DFT calculations.     

Analysis of spectral properties of acoustic noise produced during magnetic resonance imaging

Magnetic resonance imaging (MRI) technique enables non-invasive analysis of the human vocal tract during phonation. Creation of MR images of the vocal tract is accompanied by simultaneous recording of the produced speech. The paper analyzes and compares spectral properties of an acoustical noise produced by mechanical vibration of the gradient coils during scanning in the open-air MRI equipment working in a weak magnetic field with low B₀ up to 0.2 T. This noise exhibits harmonic character, so it is suitable to analyze its properties in the spectral domain. Obtained results of spectral analysis will be used to devise a new cepstral-based filtering method for noise suppression of recorded speech.