KnE Energy

2022-10-18T12:28:26+00:00

Large-scale Synthesis of Monodisperse PbS Quantum Dots

2020-03-09T09:45:42+00:00

PbS quantum dots (QDs) are a promising material for designing of modern solar energy convertors. Yet, their reproducible synthesis is still intractable, since typical methods do not allow controlling the growth of PbS nanocrystals due to the high reaction rates. Here we propose the two-step synthetic procedure, which allows controlling precisely nanocrystal growth on the second stage. The first step allows obtaining small PbS QDs by the standard hot injection method, which are then slowly grown to a desired size on the second stage. By use of this method, we were able to obtain gram-scale batches of PbS QDs with high reproducibility of the photoluminescence properties of the synthesis product.

Keywords: PbS quantum dots, nanoparticles growth, infrared luminescence

Polymeric Layers for Optical Structures with Controllable Waveguide Parameters

2020-03-09T10:18:46+00:00

Anisotropic planar waveguides based on a liquid crystal monomer with principal refractive indices n

Periodic Structures Fabricated By STED-DLW Stereolithography: Morphology and Optical Properties

2020-03-09T10:21:20+00:00

Two-dimensional (photonic antennas) and three-dimensional (photonic crystals) periodic polymer structures were fabricated by STED-DLW stereolithography. Their morphological features were studied using scanning electron microscopy and atomic force microscopy; also their optical properties were investigated by Fourier spectroscopy and confocal microscopy.

Keywords: STED-DLW stereolithography, optical properties, luminescent mapping, 3D structures

Laser Printing of Gel Microdrops with Living Cells and Microorganisms

2020-03-09T10:23:17+00:00

We report the results of experiments on laser printing (wavelength λ=1064 nm) with gel microdrops acting as carriers of living microbial and cellular objects. The dynamics of transport processes with the help of high-speed optical video was studied, which allows to determine characteristics of the formed gel jets and to optimize the operating mode of the laser. It is shown that laser pulses of 4 to 20 ns duration and energy E ≤ 20 μJ should be used to minimize the negative effect on living systems. The results can be used to optimize the technologies of cellular printing and laser engineering of microbial systems (LEMS). LEMS technology is used to isolate hard-cultivated and non-cultivated by classical methods of microorganisms that can act as producers of new biologically active substances and antibiotics.

Keywords: laser printing, gel, microdrop, living cell, microbial

Equivalent Surface Temperature of Optical Elements Interacting with Laser Irradiation

2020-03-09T10:24:21+00:00

We propose a novel technique for measuring the surface temperature distribution of optical elements interacting with high power laser radiation. This technique is based on measuring temperature sensitive piezoelectric resonance frequencies of nonlinearoptical crystals that are transparent at involved laser radiation wavelengthes. Using small thermoresonators made of the lithium niobate (LiNbO3) crystal the kinetics of the surface temperature distribution of the silica lens heated by 11W CW laser radiation at 1064 nm was measured. According to measured data, the optical absorption coefficient of the lens was evaluated to be

Methods of Interaction Field Extension for Precision Highspeed Femtosecond Laser Processing of Transparent Materials

2020-03-09T10:26:14+00:00

The results of experiments on the study of methods of the focal volume elongation in the direction of the propagation of femtosecond laser pulses are given. The lengthening of the focal volume due to linear effects - interface spherical aberration, beam self-diffraction, and nonlinear effects - Kerr self-focusing is demonstrated. The conditions and reasons for the formation of extended filamentary micromodifications with diameters about 2 μm and a length of more than 100 μm in polycarbonate samples using different methods of extending the interaction region are determined.

Keywords: femtosecond laser, microstructures, microprocessing, photodegradation, filamentation.

The Design Optimization and Experimental Investigation of the 4.4 μm Raman Laser Basedon Hydrogen-filled Revolver Silica Fiber

2020-03-09T10:29:26+00:00

Optical properties of hollow-core revolver fibers are numerically investigated depending on various parameters: the hollow-core diameter, the capillary wall thickness, the values of the minimum gap between the capillaries, the number of capillaries in the cladding and the type of glass (silica and chalcogenide). Preliminary, similar calculations are made for simple models of hollow-core fibers. Based on the obtained results, the optimal design of the revolver fiber for Raman laser frequency conversion (1.56 μm → 4.4 μm in 1H2) was determined. As a result, efficient ns-pulsed 4.42 μm Raman laser based on 1H2-filled revolver silica fiber is realized. Quantum efficiency as high as 36 % is achieved and output average power as high as 250 mW is demonstrated.

Plasma-mediated Nanosecond-Laser Generation of Si Nanoparticles in Water

2020-03-09T10:32:21+00:00

Plasma-mediated nanosecond IR-laser ablation of Si in water was describe sublinear function mass loss by multi shot ablative and third-power function extinction coefficient of generated colloidal solutions of density laser intensity. The first addiction shows influence subcritical ablative plasma to ablative rate, also fast increase extinction coefficient of 100 nm size particles of silicon in colloidal solution implies plasma-mediated dissociation of the ablation products.

Keywords: silicon nanoparticles, nanosecond laser ablation, sub-critical ablative plasma, extinction coefficient, scaling relationships, melt expulsion

Optical Properties of Gel Titanium Dioxide Film, Modified By Metal Nanoparticles

2020-03-09T10:35:11+00:00

The physic-chemical and optical properties of composite titanium dioxide films with gold, cobalt, copper, nickel and iron nanoparticles made using gel technology were studied in the work. The of titanium dioxide films structure synthesized according to different technologies is compared. The differential scanning calorimetry method was used to determine the temperatures of phase transitions of manufactured samples of various modifications of titanium dioxide. The transmission spectra of samples modified by metal nanoparticles with different concentrations were studied.

Keywords: sol-gel, gel method, titanium dioxide, modification, nanoparticles, gold, cobalt, copper, iron, nickel, spectroscopy.

Superconducting Single-photon Detectors Made of Ultra-thin VN Films

2020-03-09T10:37:55+00:00

We optimized technology of thin VN films deposition in order to study VN-based superconducting single-photon detectors. Investigation of the main VN film parameters showed that this material has lower resistivity compared to commonly used NbN. Fabricated from obtained films devices showed 100% intrinsic detection efficiency at 900 nm, at the temperature of 1.7 K starting with the bias current of 0.7·I

Preparation of Freestanding Porous Silicon Photonic Crystals

2020-03-09T10:40:50+00:00

Nowadays, the photonic crystals are of great interest and are widely used in photonics, biosensing, optoelectronics and other fields of research. The one-dimensional photonic crystals manufactured on the basis of porous silicon were proved to be the most suitable for applications due to their high sorption ability, large surface area, easiness of fabrication, and possibility to precisely control porosity and refractive index during electrochemical etching. However, the sensitivity of various kinds of gas and biological sensors as well as the performance of solar cells and other devices on the basis of porous silicon structures may be significantly increased by detaching the structures from the substrate. Here, we have developed and investigated the fabrication procedure of freestanding one-dimensional photonic crystals on the basis of porous silicon with the use of electropolishing method followed stabilization of freestanding porous silicon photonic structures through their oxidation. We have demonstrated that the developed and applied lift-off procedure does not violate the morphology and the photonic properties of the samples.

Keywords: Porous silicon, photonic crystals, microcavity, thin films, freestanding photonic crystals.

Dynamics of Changes in Optical Absorption Induced By Nanosecond Laser Pulses in the Bi12Tio20:Al Crystal

2020-03-09T10:43:18+00:00

The dynamics of the changes in optical absorption in Bi12TiO20:Al crystal at the wavelength of 655 nm, which were induced by a packet of laser pulses with the wavelength of 526.5 nm, pulse width of 10 ns, repetition frequency from 10 Hz to 1 kHz and pulse energy of 9-15 μJ had been experimentally investigated.

Keywords: light-induced absorption, bismuth titanium oxide crystal, impulse radiation

Correction of Y-Branches on Proton-exchanged Waveguides in Lithium Niobate By Femtosecond Writing Technology

2020-03-09T10:44:10+00:00

Correction Y-branches power dividers of the multi-function integrated optics chips on proton-exchanged waveguides in lithium niobate by the technology of direct femtosecond laser writing were investigated. Optimal correction parameters and their influence on temperature stability of Y-splitter are determined.

Keywords: lithium niobate, Y-splitters, proton exchange, femtosecond writing, refractive index, integrated optics.

Photoelectric Fields and Band Gap in Doped Lithium Niobate Crystals

2020-03-09T10:46:50+00:00

Photorefractive effect was researched and band gap was determined in nominally pure congruent and stoichiometric lithium niobate crystals, and in a series of congruent LiNbO3 crystals doped by Mg, Zn, B, Gd, Y, Er cations, and LiNbO3 single crystals with double doping Mg:Gd, Mg:Fe, Mg:Y, Mg:Ta by photoinduced light scattering and optical spectroscopy methods.

Keywords: lithium niobate single crystal, doping, photorefractive effect, photoinduced light scattering, optical spectroscopy, band gap

Nanogratings Formation in a System of Ultra-short Laser Pulses – Metalloorganic Gas – Deposited Metal – Sapphire in Sinergetic Interference Field with Waveguide Modes Participation

2020-03-09T10:50:27+00:00

Experimental results of laser-induced deposition of structured metal films from metalloorganic vapor have been analyzed. A new physical model has been put forward to explain the results. The model is based on the interference phenomena between the incident laser radiation and waveguide modes of a thermally induced gradient waveguide in the substrate.

Keywords: femtosecond radiation, metal deposition, interference, waveguide modes, surface nanogratings.

Conditions for the Dye Sensitization of Photoprocesses in Semiconductors

2020-03-09T10:52:21+00:00

The necessary requirements for the photoeffect sensitization are the existence of electron states in the semiconductors capable of accepting energy from the dye and subsurface band bending. Methods for control of the sensitization efficiency are discussed.

Keywords: Internal Photo Effect, Semiconductors, Dye Sensitization.

Experimental Research of XeBr Excimer Molecule Luminescence in Ar-Xe- C2HBrClF3 Gas Mixture with High Energy Particles Excitation

2020-03-09T10:53:39+00:00

The results of experimental research of spectral and time-resolved properties of XeBr excimer molecule luminescence in high-pressure gas mixtures of Ar-Xe-C2HBrClF3 under fast electron (E

Organic Chromophores with Nonlinear Optical Properties for Electro-optical Modulators

2020-03-09T10:55:06+00:00

Terahertz Radiation of a Low-inductance Discharge in Vacuum with Laser-plasma Initiation

2020-03-09T10:56:06+00:00

The results of the study of terahertz radiation, which is generated by the plasma of a low-inductance discharge with micropinchs, are presented in this paper. The discharge was initiated by focused radiation from a pulsed Nd:YAG laser (pulse duration is 10 ns, pulse energy is 0.8 J). The energy that was stored in the capacitor of the discharge system was ∼ 40 J. The principal role of micropinch for the generation of THz radiation was proposed. The oscillogram of the diode current was obtained to visualize the presence of micropinch plasma. The power of the THz source was calculated and an experimental study of the spectrum of this source was carried out.

Taking into Account the Increase in the Dye Molecules Absorptivity in Modeling of Graetzel Solar Cell with Metallic Nanoparticles

2020-03-09T10:57:30+00:00

Using a model developed by Professor Kucherenko M.G. a mathematical description of the effect of metal nanoparticles on the absorbing capacity of organic dye molecules in Graetzel cells was carried out. The enhanced absorption spectra of the dyenanoparticle system and the current-voltage characteristics of the investigated solar cells are calculated.

Dynamics of Switching Waves in a Nanofluid in a Light Field

2020-03-09T11:01:06+00:00

The dynamics of the concentration of nanofluids placed in a light field with a Gaussian intensity profile is studied theoretically. The investigation is based on the analytical and numerical solutions of the system of linearized heat conduction and convectiondiffusion equations. The convection-diffusion equation contains terms that correspond both to the Soret effect and to the transfer of nanoparticles, caused by the action of a light field on them (electrostriction). The dependence of the coefficient of thermal conductivity of the medium on the concentration is taken into account. It is shown that under these conditions single travelling waves appear in the medium, the velocity of which depends not only on the thermal physical parameters of the medium, but also on the polarization of the particles. Conditions under which the stratification of the medium is possible are found.

Calculation of Field Characteristics in Periodic Nanostructures from Composite Elements with Activated Plasmon Modes

2020-03-10T06:06:18+00:00

Modeling of the electromagnetic field of the optical frequency in periodic structures composed of parallel conducting nanorods as well as composite spherical nanoparticles with an excitonogenic envelope in hexagonal 2d-lattices - in the quasistatic approximation and the FDTD method. The qualitative agreement of these approaches is shown when calculating field characteristics in lattices of cylindrical elements.

Formation of Surface Plasmon-Polariton Vortices at Reflection from Curvilinear Boundary

2020-03-10T06:10:06+00:00

We present the results of simulation of interference of surface plasmon-polaritons (SPPs) which are falling and reflecting from the curvilinear boundary of inhomogeneity area in the metal layer. The plasmon vortices with a screw phase dislocation appear in the singular points of the field as a result of the SPP interference after reflection from the boundary of inhomogeneity in the dovetail form. The position of the plasmon vortices on the surface of metal layer can be controlled by means of the external electrostatic field. Negative charges localized at the control probes cause the change of the boundary curvature of the permittivity of inhomogeneity area on the metal layer, which leads to displacement of the vortex localization points. When the vortex is localized under the readout nanowire probe with angular thread, the maximum or minimum of the signal takes place in the probe depending on the helicity of the thread and the topological charge of the vortex.

Keywords: surface plasmon-polariton, plasmon vortex, nanowire.

The Features of Surface Plasmon-Polariton Pulses Generation Via Cooperative Effects in Waveguide Spaser

2020-03-10T06:12:57+00:00

The problem of sub-picosecond plasmon-polariton pulse formation in metal/dielectric interface due to collective decay of excited quantum dots, placed in the dielectric layer near the metal surface, is considered. Theoretical approach to selection of semiconductor quantum dots and dielectric host medium to increase the energy transmission of quantum dot collective excitations into surface plasmon-polariton modes of waveguide spaser is developed.

Polariton Propagation in Imperfect Resonantly Absorbing Bragg grating

2020-03-10T06:18:18+00:00

The nonlinear polariton transmission through resonantly absorbing Bragg grating (RABG) with randomly varying lattice spacing is studied. In this work are presented the results of numerical simulation of propagation stability of polaritonic solitary wave consisting of matter wave coupled with counter propagating light waves which propagate through dielectric medium, containing periodically placed in the dielectric waveguide thin dielectric films with metallic nanoparticles (or quantum dots, nanoagregates with nonlinear dielectric properties). The influence of lattice spacing deviations from mean value (average) of the lattice spacing is described in the model equations by random multiplicative noise set in the phases of forward and backward electric components of electromagnetic wave. As the initial condition it was used the solitary wave solution of the model describing nonlinear wave propagation in perfect nonlinear RABG. The results of numerical simulations show that phase fluctuations lead to periodic oscillations (with the period 2

Raman Nonlinearity Contribution to Spatio-Temporal Pulse Dynamics Under Filamentation in Yag Crystal

2020-03-10T06:19:43+00:00

We report on numerical study of the nonlinear pulse propagation under filamentation of femtosecond near-infrared radiation under normal dispersion regime in YAG crystal. Influence of the Raman and Kerr tandem action on a spatial and temporal dynamics of the laser pulse were discussed. We have shown that Raman nonlinearity provides an asymmetry of temporal pulse profile: the leading edge becomes more bright and propagates at larger distances in comparison with trailing edge.

Keywords: filamentation, supercontinuum generation, Raman nonlinearity.

Field Distribution into Binary Linear Waveguide Array

2020-03-11T07:03:34+00:00

The binary (two-component) linear waveguide array that is formed either from identical waveguides but with alternating distances between adjacent waveguides, or waveguides with a positive refractive index, but having distinctions in the refractive index or the waveguide thickness. The exact solution of the coupled wave equations describing the field distribution over waveguides is found. These solutions describe the discrete diffraction in the model under consideration.

Keywords: coupled waveguides, binary array, discrete diffraction, generation function method.

Spin-orbital Conversion of Bessel Light Beams By Liquid Crystal Elements

2020-03-11T07:05:46+00:00

For the first time, the spin-orbital conversion of the linearly polarized Bessel beams in the process of their propagation in the electrically-controlled liquid crystal cell has been realized experimentally. Variations in the polarization, phase, and spatial structure of the beam have been analyzed. It has been shown that, when a Bessel beam is propagating along the liquid crystal director, the generated beam is orthogonally polarized, whereas the topological charge is varied by two unities.

Keywords: Bessel light beams, spin-orbital conversion; liquid crystals

Resonance Absorption of Light By Subwavelength Diffractive Gratings

2020-03-11T07:08:42+00:00

Diffraction of light of a visible spectral range by subwavelength metal gratings is investigated theoretically and experimentally. The influence of different grating parameters (filling factor, shape and depth, material, angle of incidence, wavelength and polarization of radiation) on diffraction efficiency is investigated. The conditions are found under which there are only zero diffraction order and the minus first order. It is established that the zero order can be suppressed by selecting the depth and shape of the grating relief. High diffraction efficiency in the -1st order is observed with increasing depth of the grating relief (more than 70% at a depth h = 80 nm). It is shown that under certain conditions an effect of plasmon resonance occurs, at which there is a complete absorption of the incident radiation. The considered optical elements can be used in systems for image processing, projection displays, in the development of a variety of sensors, etc.

Keywords: subwavelength grating, diffraction efficiency, plasmon resonance

Forming of the Optical Beam with the Rotating Polarization Vector

2020-03-11T07:09:59+00:00

A method for the optical beam production with the rotating polarization vector based on the interference of two beams with the circular polarizations is proposed. The frequency shift between beams is implemented by means of acousto-optic (AO) diffraction. The method is used for the amplitude light modulation with the frequency nf where f is acoustic frequency and n is integer. AO modulators are fabricated from paratellurite crystal. Modulators allow modulating the optical radiation with wavelength of 0.63 mcm at the quadruple frequency of the acoustic wave. The modulation frequency achieves 180 MHz.

Keywords: acousto-optic diffraction, Bragg regime, frequency shift, rotating polarization vector.

Manipulation of Microparticles By Bessel Light Beam

2020-03-11T07:13:46+00:00

We consider perspectives of optical manipulation of microscopic objects in the area of biology, biophysics and medicine. The first part of the work is devoted to a brief review of the microparticles’ manipulation. The second part contains calculations of the focusing of laser radiation parameters and some results on the formation of Bessel light beams. The experimental setup based on the optical manipulation technique of micron-sized particles was developed.

Vortex Interferometric Microscopy with Laguerre-Gaussian Beams

2020-03-11T07:17:26+00:00

In the present research, we discuss the results of analysis of coherent light beams carrying an optical vortex and propagating through the isotropic medium with a complex surface microrelief and its application to super resolution microscopy. It was shown, that phase analysis of singular beam with single charged centered optical vortex allow to retrieve information about sample surface relief. High spatial resolution caused by vortex helical phase sensitivity to disturbances in wave front after reflection or spreading through studying sample, which can be optically transparent or have a reflecting surface. This method applicable for non-destructive testing of live cells and biological tissues in real-time regime with exceeding optical diffraction limit. Vertical resolution of a microscope based on the phase singularity of Laguerre-Gaussian beams of low order can be achieved down to 5,27 nm for helium-neon laser source for optically transparent and reflecting surfaces.

Keywords: optical vortex, phase, microscopy, singularity

Method of Laser Cross-correlation Optical Spectroscopy for Investigation of Dispersion Medium

2020-03-11T07:25:13+00:00

In the paper, we suggest one of the possible schemes of a cross-correlation optical spectroscopicdevice for investigation of turbid colloidal solutions and suspensions. This devise is designed fordeterminationof the hydrodynamic radii of nanoparticles. The cross-correlation function is constructed for two signals of light intensity scattered on a cuvette with the investigated dispersion medium. The construction of crosscorrelation optical spectroscopicdevice makes it possible to detect single scattered light by suppressing multiple scattering. We carried out an analysis of literature containing theory of light scattering and results of applying cross-correlation method for investigation of solutions and suspensions. Based on the analytical review, the scheme of cross-correlation optical spectroscopicdevice was developed and constructed.

Keywords: specklefield, cross-correlation, optical spectroscopy, size distribution, dispersion medium

Laser Desorption of Traces of Explosives in Ion Mobility Spectrometry

2020-03-11T07:26:28+00:00

The efficiency of a YAG:Nd3+laser (λ = 1064 nm) and a diode continuous laser (λ = 440 nm) to initiate laser desorption of traces of trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) is quantitatively compared with use of mass spectrometry. It is shown that a pulsed neodymium laser is more promising for creating a device of contactless sampling for ion mobility spectrometers.

Laser Conoscopy Study of Optical Anomalies in Uniaxial Crystals

2020-03-11T07:27:42+00:00

New experimental possibilities of detecting fine optical anomalies in uniaxial crystals are demonstrated on a level with numerical estimation of refractive index and mechanical stress variations that cause distortions of the optical indicatrix. New possibilities are due to the use of an exact equation for isochromes derived for uniaxial crystals without mathematical simplifications commonly used by other authors. It allows one to calculate and graphically reproduce the theoretical form of isochromes of any orders in the conoscopic picture of an ideal crystal with known principal refractive indices, the thickness and orientation of the crystal surfaces, and also the wavelength of the radiation and the parameters of the optical circuit. A computer comparison of the theoretical image with an experimental conoscopic picture of a real crystal, fixed by a color digital camera on a semitransparent screen, is performed. The data on the variations of refractive indices and mechanical stresses in the crystal are retrieved from the mathematical processing of differences in the conoscopic images. The applications of the proposed method for the analysis of optical homogeneity of paratellurite and lithium niobate single crystals are presented.

Keywords: method of conoscopy, isochromes, piezo-optic effect

Registration of CBS Effects from Wedge-shaped Samples Containing Particles of Alumina

2020-03-11T07:28:39+00:00

The paper looks at recent results of research dealing with a coherent backscattering (CBS) on the particles of alumina. It was developed a system of registration of CBS with a tunable dynamic sample. During the experiment the transport mean free path over the width of the peak of angular profile of signal intensity of CBS was determined. Moreover, new scientific data about the CBS’s profiles from randomly inhomogeneous environments were obtained.

Scattered Light Measurement for the Birefringence Distribution Estimations

2020-03-11T07:53:02+00:00

The technique based on the digital processing of recorded scattered light distribution enabling for the measurement of the birefringence profile in non-uniform anisotropic materials was proposed.

Keywords: measurement technique, birefringence distribution, scattered light, tempered glass

The Laser-only Single-event Effects Test Method for Spacecraft Electronics Based on Ultrashort-pulsed-laser Local Irradiation

2020-03-11T07:55:06+00:00

The substantive laser method for studying the radiation hardness of semiconductor devices, not requiring calibration by ions, called ”local irradiation”, is described. The essence of the local approach is in irradiating the sample sensitive volume with the ultrashort-pulsed laser beam at some distance from its focus plane, where the beam becomes rather wide and divergent. Assuming the single-photon absorption, the relationship between the laser pulse energy and the excess charge actually generated in irradiated sensitive volume is obtained by accurate measurement of the electrical response, that makes possible to take into account non-uniform optical losses and avoid additional calibration by ions. Some results, obtained using both the front-side and the backside local irradiation of devices, are presented. Comparison with results obtained by traditional methods using focused laser radiation with subsequent calibration by ions showed that laser-only measurements, based on described local irradiation, give the correct estimates of radiation hardness parameters.

Keywords: Ultrashort laser pulse, single-event effect, local laser irradiation, semiconductor device, integrated circuit.

Refraction of the Flat Optical Beam in a Transparent Heterogeneous Environments

2020-03-11T07:56:09+00:00

Presents a method of visualization and laser diagnostics of optically inhomogeneous media based on the phenomenon of refraction of the structured laser radiation (SLR). The described method of studies of the diffusion layer of the optical refractography method. Experimental setup for digital recording refractive pattern (refractograms). Shown for examples application of methods of the laser refractography thermal processes.

Investigation of the Characteristics of the Three-axis Ring Typed Angular Velocity Transducer Based on Optical Tunneling Effect

2020-03-11T08:11:32+00:00

The structure of a three-axis ring type angular velocity transducer based on the optical tunnel effect (OTE) is proposed. In this article considered the primary motion, which is excited by the electrostatic means and on the secondary displacements which provide the applied angular velocity information.

Keywords: three-axis transducer, angular velocity, optical tunneling effect, ring resonator.

Application of Laser Radiation for Fabrication of Micromechanical Actuator Based on Two-Way Shape Memory Effect

2020-03-11T08:13:03+00:00

The work deals with production and research of experimental samples of micromechanical actuator based on the rapidly quenched TiNiCu alloy, in which a two-way shape memory effect is formed as result of impact of the laser radiation. By the technique of focused ion beams an element with thickness of 5 microns, width of 7 microns and 100 microns in length was obtained, bending reversibly to 2.5 microns in the heating-cooling cycle.

Keywords: shape-memory alloy, thin ribbon, two-way shape memory effect, laser treatment, micromechanical actuator

Optoelectronic Methods of IR-Photometry in Solving Thermal and Physical Problems

2020-03-15T07:55:45+00:00

Results of the application of optoelectronic IR-photometry methods for solving the actual thermophysical problems using high-speed photodiode temperature (pyrometric) sensors are presented. The latest achievements of the Ioffe Institute in the field of middle IR spectral range (3-6 μm) photodiode production technology are used in the sensor development. The above-mentioned middle-IR photodiode sensors are based on heterostructures from A3B5 solid solutions and they do not require forced cooling. New data on thermophysical processes taking place under the complex experimental conditions, including dynamically changing properties of the object, have been obtained. The new experimental results are based on high-speed non-contact measurements of the absolute temperature of objects directly in the exposure region of laser radiation and / or powerful electromagnetic fields. In the context of creating new experimental techniques for determining the thermophysical parameters of new promising materials the efficiency of middle- IR photodiode temperature sensors has been shown. In particular, a simple and effective measuring method for determining the heat transfer coefficient of solid objects and the pyroelectric coefficient of ferro- and pyroelectric materials is offered. The measuring method is based on laser thermowave techniques and direct noncontact measurements of the sample surface temperature under the pulsed / periodic laser action. The proposed experimental techniques make it possible to significantly improve the accuracy of measurements of thermophysical parameters of materials, and in particular, to eliminate a considerable spread of data on the parameters of the pyroelectric effect in ferroelectric materials.

Keywords: Pyrometric sensors, mid-IR photodiodes, laser thermowave techniques, heat transfer coefficient, pyroelectric coefficient

Piezoelectric Resonance Temperature Sensor for Active Fibers

2020-03-15T08:00:53+00:00

A novel method for temperature measurement of active fibers under conditions of

lasing and radiation amplification is introduced. This method allows determination of the longitudinal temperature distribution of active fibers at different optical pump powers. A piezoelectric resonator made of the quartz crystal in the form of a hollow cylinder is used as a temperature sensor. Investigated segment of the active fiber is put thorough the hole of the resonator. Heating temperature of the resonator is determined by measuring a frequency shift of the piezoelectric resonance, which is preliminary calibrated under uniform heating conditions. In order to evaluate the heating temperature of the investigated fiber segment, the last one was substituted with a copper wire coated with polymer. A copper wire was heated by transmitting an electric current and its temperature was determined by measuring the resistance change. Numerical simulations revealed that the heating temperatures of the active and copper fibers differ by less than 9% at 11 W/m thermal load level. Heat transfer coefficient was evaluated using cooling kinetics and stationary state temperature of the ”copper” fiber. Heating temperature of the active fiber of the ytterbium fiber laser was measured at different pump levels (up to 150W).

Keywords: optical fiber, active fiber heating, fiber laser, temperature sensor, piezoelectric resonance

Study of Gamma-ray Induced Attenuation of Fluorine-doped Single-mode Radiation Hard Optic Fiber

2020-03-15T08:03:35+00:00

The paper presents the measurements results of optic fiber’s radiation induced attenuation. The approach of optic fiber’s radiation test at negative temperatures is introduced. The results of an investigation of the decay of an optical signal during a pulsed electron.

Keywords: radiation hardness, fiber-optic communication, radiation-induced attenuation

A Determination of the Initial Level of the Brillouin Frequency Shift in Optical Fibers of Different Kinds

2020-03-15T08:22:41+00:00

A dependence of the hyper-acoustic wave velocity on characteristics of the optical fiber core is analyzed in this paper. The values of Brillouin frequency shifts for various types of optical fibers at room temperature and without longitudinal tensile force are presented. Having database of profiles of the Mandelstam – Brillouin backscattering spectrums for fibers of different kinds and manufacturers allow to classify the optical fibers in the optical cables and detect damaged sections of fiber optical communication line.

Keywords: optical fiber, strain, Brillouin frequency shift, Brillouin reflectometry, hyper-acoustic wave.

Use of 3×3 Coupler in the Fiber Optic Strainmeter Based on Mach-Zehnder Interferometer

2020-03-15T08:23:38+00:00

In this paper a strainmeter based on the fiber optic Mach-Zehnder interferometer with 3x3 coupler for a phase shift demodulation is presented. Laboratory experiments on registration of harmonic deformation with the use of strainmeter were carried out. The experiment demonstrates efficiency of the strainmeter.

Keywords: strainmeter, interferometer, coupler

Research of Quantum Well Laser Diode’s and Heterostructural P-I-N Photodiode’s of Fiber-Optic Modules Radiation Hardness to Gamma-ray and Neutron Irradiation

2020-03-15T08:29:47+00:00

The paper presents the measurements results of optical and electrical parameters of quantum well laser diodes and heteroepitaxial photodiodes under gamma-ray and neutron irradiation. The testing results of transceiver modules gamma irradiation tolerance are introduced. The most vulnerable elements of module are highlighted.

Keywords: laser diode, photodiode, radiation hardness, VCSEL, transceiver modules, fiber-optic communication

The application of the Raman Spectroscopy Method for Evaluating Implants from the Dura Mater

2020-03-15T08:32:00+00:00

The results of a comparative spectral evaluation of the component composition of the surfaces of implants from the dura mater manufactured using the Lioplast technology with the use of ultrasound and sterilization are presented. Based on the analysis, coefficients were introduced reflecting the change in the relative concentration of components that determine the quality of the implants. It is established that Raman spectroscopy can be used to assess the change in the composition of implants based on the dura mater during their manufacture.

Keywords: Raman spectroscopy, coefficients, spectral features, implants, dura mater.

On the Difference in Action of the Laser Light with Wavelength Near 2mm on Biotissue in Gas and Water Media

2020-03-15T08:40:20+00:00

It is shown that unlike action in the air environment, section of the biotissue in the water environment (physiological solution) is performed by the steam-gas stream which is formed as a result of superintensive boiling in thin (about 0.1 mm) a liquid layer in which absorbed laser radiation. Coagulation of the biotissue, adjacent to a section, happens due to heat which is produced via vapor condensation.

Keywords: laser radiation in urology, a laser enucleation of the BPH, laser removal of the bladder cancer.

Spectral Studies of Rat Bone Tissue in Modeling Osteoporosis and Effectiveness of Treatment By Hydroxyapatite

2020-03-15T08:47:15+00:00

Presents the result of experiments on the study of the model of osteoporosis in rats using Raman spectroscopy and the effectiveness of its treatment with hydroxyapatite. Were revealed spectral differences between groups of samples (control group, group with the model of osteoporosis and a group with the model of osteoporosis after treatment with hydroxyapatite). In addition, optical coefficients were introduced to evaluate the effectiveness of treatment.

Keywords: Raman spectroscopy, optical coefficients, osteoporosis, hydroxyapatite, collagen matrix

Determination of Diffusion Coefficient in Hydrogel

2020-03-15T08:49:05+00:00

Background Oriented Schlieren method was used to obtain diffusion coefficient of glucose in hydrogel in the experiment with radial symmetry.

Keywords: background oriented schlieren, diffusion, hydrogel, holographic sensors, glucose.

Plasmonic Magnetooptic Structures for Visualization of Magnetic Information

2020-03-15T08:53:29+00:00

Optical head with magnetized garnet layer is used to detect presence of thin ferromagnetic layers such as printed text. Mathematical model of the system was created. Incident P-polarized light affected by garnet layer changes its polarization due to Faraday effect. We can detect presence or absence of magnetic information after studying changes in polarization of the reflected light.

Keywords: Magnetoplasmonic, Faraday effect, magnetoplasmonic structure, Magneto-optic plasmon resonance.

Holographic Structure Transfer from Dichromated Gelatin Layers to a Polymethylmethacrylate Substrate

2020-03-15T08:55:39+00:00

It is shown that the formation of a holographic structure on the polymethylmethacrylate (PMMA) surface is based on the use of the destructive effect of short-wave UV radiation with a wavelength less than 270 nm through windows previously formed in a thin layer of dichromated gelatin (DCG) covering the substrate. The optimization of the PMMA surface treatment by isopropanol and methylisobutyl ketone (MIBK) developers was made, which allowed creating on the PMMA substrates relief-phase holographic gratings with the high diffraction efficiency (DE) of about 25% and maximum depth of the surface relief of the order of 1 μm.

Keywords: holographic gratings, surface relief, UV radiation, dichromated gelatin, polymethylmethacrylate, methylisobutyl ketone (MIBK).

Analysis of Temperature Modes of Hologram Recording on Photothermoplastic Materials

2020-03-15T09:05:11+00:00

Theoretical study of the process of hologram recording on photothermoplastic media

in which a linear relationship between the change in the refractive index and the

temperature expansion of the medium is assumed. The results of the study allow us

to estimate the required laser radiation power for the information recording as the

function of the spatial frequency and the radiation exposure duration.

A solution was found for the heat conduction equation for photothermoplastic

materials heated by an interference laser field. The solution obtained allows us

to determine the required value of the recording temperature for given spatial

frequencies, depending on the thermophysical parameters of the medium, and also

on the power and duration of the heating radiation.The use of the results of the study made it possible to find analytical expressions for the dependence of the diffraction efficiency of thermal gratings on the spatial frequency, pulse duration, and thermophysical parameters of the medium. It is established that to increase the recording density in these media, materials with a low thermal diffusivity are necessary, while recording should be performed by the short pulses to minimize the length of thermal diffusion.

Keywords: Diffraction efficiency; Hologram; Photothermoplastic materials; Temperature; Heating

Phase Filters for 3D Localization of Point Light Sources

2020-03-15T09:08:43+00:00

The work relates to the engineering and research of phase filters for three-dimensional localization of point light emitters. These phase filters form a light field having two clearly visible maxima in their intensity distribution (i.e. two-lobe fields). By means of numerical simulation, the influence of the amplitude and phase distortions of the wave front of the illuminating beam on the two-lobe field formation has been studied in the work.

Keywords: spiral light beams, amplitude distortions, phase distortions, threedimensional localization, two-lobe field.

Study of Dimensional Stability of Metal-ceramic Prostheses By Holographic Interferometry

2020-03-15T09:09:30+00:00

Presents results of a study of deformation of metal-ceramic bridge prostheses manufactured in a variety of ways. Registration of deformations was carried out using double-exposure holographic interferometry. According to the experimental data, an optimal method of making dentures.

Keywords: bridge prosthesis, deformation, holographic interferometry, the method of two exposures

Determination of the Working Liquids Technical Condition By Analysis of Digital Speckle Images Parameters

2020-03-15T09:11:01+00:00

The article discusses the practical realization for the optical control method of technical working fluids condition by the analysis of digital speckle images parameters is discussed. The experimental research results on the application of this method for estimation of aviation fuel and motor oil technical condition are presented.

Keywords: motor oil, aviation fuel, speckle, autocorrelation, impurities, diagnostics

Method of Asymmetric Optical Encryption of Images Using Spatially Incoherent Illumination

2020-03-15T09:13:39+00:00

The method of asymmetric encryption of images based on the double optical encryption with spatially incoherent illumination is presented. Numerical simulations of the presented method in various modifications are carried out and their efficiency is estimated. The modification providing the best balance between maintaining the advantages peculiar to the optical encryption and quality of the decoded images is chosen. In this case the value of the normalized standard deviation (NSTD) of the decoded image from original one for asymmetric encryption differs no more than by 8% from NSTD of standard optical encryption with spatially incoherent illumination.

Objects Reconstruction By Compressive Sensing from Single-pixel Registrations Using DMD

2020-03-15T09:17:25+00:00

Compressive sensing allows to reconstruct information from a number of sparse signals. Use of digital micromirror device (DMD) between object and single-pixel detector planes is example of sparse signals registration technique. Detection of illumination from the objects by a single-pixel detector using a DMD was modeled. Grayscale, binary and color object images were used as objects. By compressed sensing images obtained under various recording conditions were reconstructed. Obtained results were analyzed. Reconstruction quality estimations and processing times are given.

Keywords: compressed sensing, single-pixel imaging, digital micromirror device, image quality.

Coefficients Quantization at Off-axis Digital Hologram Wavelet Compression

2020-03-15T09:20:46+00:00

Digital holographic information is compressed for storage of 2D- or 3D-objects amplitude and phase distributions, fast transmission, analyzing and displaying of these data. In this paper features of application of wavelet transforms for off-axis digital holograms compression are considered. The combined technique based on zero and twin orders elimination, wavelet compression of the amplitude and phase components of obtained Fourier spectrum and further additional compression of wavelet coefficients by thresholding and quantization is analyzed. Numerical experiments on reconstruction of images from the compressed holograms are performed. The comparative analysis of applicability of various wavelets and additional quantization of coefficients is performed. Obtained results demonstrate possibility of 180 and more times compression using iterative and noniterative methods of coefficients quantization and threshold zeroing less 80% of wavelet coefficients.

Keywords: digital holography, hologram compression, wavelets, quantization, thresholding, digital image processing.

Optical-electronic System and Software Complex for Research and Identification of Macro- and Micro-optical Elements of Security Holograms

2020-03-15T09:21:46+00:00

The paper presents an automated optical-electronic software and hardware complex for carrying out activities to identify and control the authenticity of diffraction and holographic optical security elements. The developed complex makes it possible to significantly simplify the work of the expert in conducting forensic studies of objects marked with security holograms.

Zero Order Correction of Shift-multiplexed Computer Generated Fourier Holograms Recorded in Incoherent Projection Scheme

2020-03-15T09:23:17+00:00

Application of computer holography methods provides the possibility to obtain the high quality holograms of objects that exist as digital models without the necessity of complex and high precision optical schemes. Computer generated Fourier holograms (CGFH) are widely used for record and optical restoration of relatively simple 2D raster objects. Application of incoherent photolithography methods such as incoherent projection allows the record of CGFHs as micro-holograms onto the photosensitiv medium with desired reduction of hologram sizes using relatively simple optical setup. The reconstruction optical schemes of CGFHs can be implemented in augmented reality displays and optical sight indicators. In this article the specificity of CGFH shift-multiplexed record process and particularly the method of zero order correction is discussed.

Keywords: computer generated hologram, Fourier hologram, incoherent projection scheme.