Low-Coherence Integrated Optical Interferometer for Fibre Optic Sensors.

This paper proposes and implements a novel scheme for recording signals from fibre optic sensors based on tandem low-coherence interferometry with an integrated optical reference interferometer. The circuit allows precision control of the phase shift. Additionally, the paper illustrates the potential for detecting vibration and object deformation using fibre optic Fabry-Perot sensors connected to the registration system.

Polarization-resolved resonant Raman excitation of surface and bulk electronic bands and phonons in MBE-grown topological insulator thin films.

Interaction of phonons with Dirac-like electronic states sets the fundamental limit of electron transport in topological insulators (TIs). Polarization-resolved and resonant Raman scattering of bulk and surface electronic excitation and vibrational modes in BiTe and BiSbTeSe (BSTS) thin films was investigated. At photon energies () of 1.

Investigation of Hf/Ti bilayers for the development of transition-edge sensor microcalorimeters.

The superconducting properties of 85 nm thick hafnium thin films with a 5 nm thick titanium layer on top have been investigated for three different geometries, that is, a film covering the entire 7 × 7 mm chip surface, bridges with a width of 200 μm and length up to 1800 μm, and bridges in the form of squares with sides from 100 to 1000 μm. The bridges were formed by a photolithographic lift-off process and are intended to be used as the main sensing element of a microcalorimeter based on a transition-edge sensor (TES) in experiments to determine the magnetic moment of neutrinos. Based on the measurements of the critical current, the critical temperature, and the width of the superconducting transition, we estimate the energy resolution δ of the TES prototypes, showing that it is possible to fabricate microcalorimeters with δ less than 1 eV using these films.

Probing multi-mobility edges in quasiperiodic mosaic lattices.

The mobility edge (ME) is a crucial concept in understanding localization physics, marking the critical transition between extended and localized states in the energy spectrum. Anderson localization scaling theory predicts the absence of ME in lower dimensional systems. Hence, the search for exact MEs, particularly for single particles in lower dimensions, has recently garnered significant interest in both theoretical and experimental studies, resulting in notable progress.

Effective removal of global tilt from atomically-resolved topography images of vicinal surfaces with narrow terraces.

The main feature of vicinal surfaces of crystals characterized by the Miller indices (hhm) is rather small width (less than 10 nm) and substantially large length (more than 200 nm) of atomically-flat terraces. This makes difficult to apply standard methods of image processing and correct visualization of crystalline lattices at the terraces and multiatomic steps. Here we consider two procedures allowing us to minimize effects of both small-scale noise and global tilt of sample: (i) analysis of the difference of two Gaussian blurred images, and (ii) subtraction of the plane, whose parameters are determined by optimization of the histogram of the visible heights, from raw topography image.

The diamond-silicon carbide composite Skeleton as a promising material for substrates of intense X-ray beam optics.

The paper considers the possibility of using the diamond-silicon carbide composite Skeleton with a technological coating of polycrystalline silicon as a substrate for X-ray mirrors used with powerful synchrotron radiation sources (third+ and fourth generation). Samples were studied after polishing to provide the following surface parameters: root-mean-square flatness ≃ 50 nm, micro-roughness on the frame 2 µm × 2 µm σ ≃ 0.15 nm.

Observation of reentrant metal-insulator transition in a random-dimer disordered SSH lattice.

The interrelationship between localization, quantum transport, and disorder has remained a fascinating focus in scientific research. Traditionally, it has been widely accepted in the physics community that in one-dimensional systems, as disorder increases, localization intensifies, triggering a metal-insulator transition. However, a recent theoretical investigation [Phys.

Raman scattering spectroscopy of MBE grown thin film topological insulator BiSbTeSe.

BSTS epitaxial thin film topological insulators were grown using the MBE technique on two different types of substrates , Si (111) and SiC/graphene with BiSbTeSe and BiSbTeSe, respectively. The crystallographic properties of BSTS films were investigated X-ray diffraction, which showed the strongest reflections from the (0 0 ) facets corresponding to the rhombohedral phase. Superior epitaxial growth, homogeneous thickness, smooth surfaces, and larger unit cell parameters were observed for the films grown on the Si substrate.

ac Hall Effect and Photon Drag of Superconducting Condensates.

We suggest a theoretical description of the photogalvanic phenomena arising in superconducting condensates in the field of electromagnetic wave. The ac Hall effect and photon drag are shown to originate from the second-order nonlinear response of superconducting carriers caused by the suppression of their concentration due to the combined influence of the electron-hole asymmetry and charge imbalance generated by the incident electromagnetic wave. Starting from the time-dependent Ginzburg-Landau theory with the complex relaxation constant, we develop a phenomenological description of these phenomena and investigate the resulting behavior of the dc supercurrent and second harmonic induced by microwave radiation incident on a superconductor surface.

Investigation of structural and reflective characteristics of short-period Mo/BC multilayer X-ray mirrors.

The results of a study of the structural and reflective characteristics of short-period multilayer X-ray mirrors based on Mo/BC at wavelengths 1.54 Å, 9.89 Å and 17.

Low-Coherence Homodyne Interferometer for Sub-Megahertz Fiber Optic Sensor Readout.

This study proposes a method for interferometric fiber optic sensor readouts. The method utilizes the advantages of the active homodyne demodulation technique and low-coherence interferometry. The usage of the tandem low-coherence interferometer enables modulating the reference interferometer without any changes to the sensor.

Light-emitting diodes with Ge(Si) nanoislands embedded in photonic crystals.

Room temperature lateral p-i-nlight-emitting diodes (LEDs) with photonic crystals embedded in the i-region were fabricated on structures with Ge(Si) self-assembled islands and their optical properties were investigated. The use of preliminary amorphization and solid phase epitaxy of the implanted pand ncontact regions made it possible to reduce the impurity activation temperature from 800 °С-1100 °С to 600 °С, which corresponds to the growth temperature of Ge(Si) islands. This resulted in a significant reduction of the detrimental effect of the high-temperature annealing used for diode formation on the intensity and spectral position of the luminescence signal from the islands.

Measurements of dichroic bow-tie antenna arrays with integrated cold-electron bolometers using YBCO oscillators.

We consider properties of dichroic antenna arrays on a silicon substrate with integrated cold-electron bolometers to detect radiation at frequencies of 210 and 240 GHz. This frequency range is widely used in cosmic microwave background experiments in space, balloon, and ground-based missions such as BICEP Array, LSPE, LiteBIRD, QUBIC, Simons Observatory, and AliCPT. As a direct radiation detector, we use cold-electron bolometers, which have high sensitivity and a wide operating frequency range, as well as immunity to spurious cosmic rays.

Investigation of Hafnium Thin Films for Design of TES Microcalorimeters.

Hafnium is a superconductor with a transition temperature slightly above 100 mK. This makes it attractive for such applications as microcalorimeters with high energy resolution. We report the superconducting properties of Hf films of thicknesses ranging from 60 to 115 nm, deposited on Si and AlO substrates by electron beam evaporation.

Absence of Mobility Edge in Short-Range Uncorrelated Disordered Model: Coexistence of Localized and Extended States.

Unlike the well-known Mott's argument that extended and localized states should not coexist at the same energy in a generic random potential, we formulate the main principles and provide an example of a nearest-neighbor tight-binding disordered model which carries both localized and extended states without forming the mobility edge. Unexpectedly, this example appears to be given by a well-studied β ensemble with independently distributed random diagonal potential and inhomogeneous kinetic hopping terms. In order to analytically tackle the problem, we locally map the above model to the 1D Anderson model with matrix-size- and position-dependent hopping and confirm the coexistence of localized and extended states, which is shown to be robust to the perturbations of both potential and kinetic terms due to the separation of the above states in space.

Luminescence of In(III)Cl-etioporphyrin-I.

The luminescent and photophysical properties of the etioporphyrin-I complex with indium(III) chloride, InCl-EtioP-I were experimentally studied at room and liquid nitrogen temperatures in pure and mixed toluene solutions. At 77 K, in a 1:2 mixture of toluene with diethyl ether, the quantum yield of phosphorescence reaches 10.2%, while the duration of phosphorescence is 17 ms.

Emission Enhancement of Ge/Si Quantum Dots in Hybrid Structures with Subwavelength Lattice of Al Nanodisks.

The effects of resonance interaction of plasmonic and photonic modes in hybrid metal-dielectric structures with square Al nanodisk lattices coupled with a Si waveguide layer were investigated using micro-photoluminescence (micro-PL) spectroscopy. As radiation sources, GeSi quantum dots were embedded in the waveguide. A set of narrow PL peaks superimposed on the broad bands were observed in the range of quantum dot emissions.

A method for estimating magnetic field of TEM objective lens.

We propose a method for calibration of magnetic field in the objective lens of transmission electron microscope. The calibration process is based on classical Fresnel imaging of Permalloy disks and measuring the displacement of the magnetic vortex core when the sample is tilted at various excitations of the objective lens. We adopted the Carl Zeiss LIBRA 200 MC transmission electron microscope for Lorentz electron microscopy using this method.

Lanthanide Coordination Polymers with Soft-Base Ditopic Bisthiazolate Ligands.

In order to prepare the first lanthanide coordination polymers (CPs) based on ditopic sulfide ligands, benzo[1,2-:4,5-']bisthiazole-2,6(3,7)-dithione (HL) was used as a linker. The reactions of lanthanide silylamides Ln[N(SiMe)] (Ln = Nd, Gd, Er, and Yb) with HL result in the formation of soluble dimethyl sulfoxide (DMSO) ionic salts [Ln(DMSO)][L] [Ln = Nd (), Gd (), Er (), and Yb ()]. Due to the lack of coordination of anionic ligands, compounds , , and do not show sensitized metal-centered photoluminescence (PL), while Gd compound shows weak phosphorescence at 77 K.

Tuning the Luminescence Response of an Air-Hole Photonic Crystal Slab Using Etching Depth Variation.

Detailed studies of the luminescent properties of the Si-based 2D photonic crystal (PhC) slabs with air holes of various depths are reported. Ge self-assembled quantum dots served as an internal light source. It was obtained that changing the air hole depth is a powerful tool which allows tuning of the optical properties of the PhC.

An Indium Synthetic Etioporphyrin for Organic Electronics: Aggregation and Photoconductivity in Thin Films.

A new complex of indium(III)chloride with etioporphyrin-I was synthesized and characterized. As with naturally occurring extraligated etioporphyrins, the InCl-EtioP-I spectrum in solution has a very strong B-band and a more than an order of magnitude weaker Q-band, but this difference diminishes in solid films of InCl-EtioP-I obtained by thermal evaporation in vacuum. In a solid, molecules have a tight convex-convex arrangement in a 2D double layered structure with interplane distance of 3.

Iron(II) Complexes with Porphyrin and Tetrabenzoporphyrin: CASSCF/MCQDPT2 Study of the Electronic Structures and UV-Vis Spectra by sTD-DFT.

The geometry and electronic structures of iron(II) complexes with porphyrin () and tetrabenzoporphyrin () in ground and low-lying excited electronic states are determined by DFT (PBE0/def2-TZVP) calculations and the complete active space self-consistent field (CASSCF) method, followed by the multiconfigurational quasi-degenerate second-order perturbation theory (MCQDPT2) approach to determine the dynamic electron correlation. The minima on the potential energy surfaces (PESs) of the ground (A) and low-lying, high-spin (A) electronic states correspond to the planar structures of and with symmetry. According to the results of the MCQDPT2 calculations, the wave functions of the A and A electronic states are single determinant.

Microwave Near-Field Dynamical Tomography of Thorax at Pulmonary and Cardiovascular Activity.

The developed near-field microwave diagnostics of dynamical lung tomography provide information about variations of air and blood content depth structure in the processes of breathing and heart beating that are unattainable for other available methods. The method of dynamical pulse 1D tomography (profiling) is based on solving the corresponding nonlinear ill-posed inverse problem in the extremely complicated case of the strongly absorbing frequency-dispersive layered medium with the dual regularization method-a new Lagrange approach in the theory of ill-posed problems. This method has been realized experimentally by data of bistatic measurements with two electrically small bow-tie antennas that provide a subwavelength resolution.