3D models of piezoelectric and optical elements which assembled from microstructures of a certain geometry were developed. These models were prepared for printing on a 3D printer, considering the specifics of their geometry and the small size of each of the cells. After several printing attempts, designed prototypes were obtained using SLA technology with synthesized plastics. These prototypes were investigated for the presence of defects and the quality of the resulting elements (preservation of the necessary microcell structures). An analysis was carried out and a technology for printing elements of this type on a 3D printer was obtained. These designs can be used in practice as piezoelectric or piezoacoustic elements when a piezoelectric powder is added to a polymer, for example, in ultrasonic flowmeters, or used to create optical structures, for example, diffractive optical elements. They will have properties different from the properties of elements obtained by standard methods, due to using of microcells with a certain geometry in their constructions.
The work is devoted to the problem of three-dimensional models of flow profiles in the hydrodynamic system’s channels restorating. A multichannel ultrasonic flow meter based on the time-pulse method was developed and investigated for measuring velocity and visualizing of liquid and gas flows structures. The device determines the downstream and upstream time of an ultrasonic pulse flight in three channels and converts it into flow velocity and then into volumetric flow. A technology that allows to synchronize parallel tasks is used to organize the stable operation of the microcontroller. The main problems of technology implementation were the large amount of memory occupied and the low "transparency" of processes. The problems of the memory optimization and minimizing of power consumption was solved.
The development of piezoelectric and optical elements from microcells was carried out and models were prepared for printing on a 3D printer. These designs can be practically used as piezoacoustic or piezoelectric sensors, if added to the composition of the piezoelectric powder, for example, in ultrasonic flow meters, or used to create optical structures, for example, diffractive optical elements. Elements obtained by 3D printing will have properties that differ from the properties of elements obtained by standard methods.
The problem with existing flow meters is a relatively high measurement error, which is associated with a lack of information on the flow profile. In order to create a reference device that makes it possible to study the flow profile due to a larger number of sensors, with bore size 50 mm primary transducer with fourteen channels is developing and manufacturing. This device can provide more accurate results due to the use of multiple channels of ultrasonic signal passage, which makes it possible to calculate large time points along the entire section of the pipe, as well as the ability to visualize the flow profile. In the course of the work, a 3D model of the primary transducer was developed in accordance with the requirements and conditions for the passage of ultrasound through a liquid medium, when it was necessary to take into account the simultaneous operation of several channels at once, taking into account the fact that the paths of ultrasound passage should not intersect. Processing several signals at once becomes possible, since five TDC microcontrollers will be used for all channels.
The paper presents an experimental study of the possibility of constructing a near-infrared atmospheric optical communication system based on a pair of 100Base-TX / 1000BASE-T signal format media converters in the 1000BASESX / LX format with DEM-310GT SFP transceivers. To ensure better stability of the input of radiation coming from the receiving collimator into the fiber cable, the FTB900 SN-Y4 BRANCHED TUBE cable was used. Its cable connector has been modified to match the DEM-310GT transceiver. The collimator of the transmitting radiation is supplemented by a spiral phase plate forming a vortex beam. The influence of atmospheric influence on the data transfer rate is analyzed.
We compare femtosecond hollow-core multifilament arrays created in the air with a TEM11 phase plate and a Dammann diffraction grating under additional loose focusing. Phase shifts introduced into the beam by the phase plate lead to zero intensity lines, which prevent transverse energy flow and filament merging. The Dammann grating forms four spatially separated energy reservoirs near the focus due to the interference. Transverse multifilament structure obtained using the Dammann grating is more resistant to phase and amplitude distortions of the initial laser beam. Plasma density inside the multifilament arrays does not exceed the value in a single filament, obtained without DOEs.
The propagation of vortex beams of wavelength 1530 nm through an aerosol and turbulent atmosphere was experimentally investigated. The stability of a vortex phase under the beam wandering caused by a flow of warm air was experimentally showed. The results obtained can be used for optical atmospheric communication.
An interference polarizer for forming a radially-polarized zero-order vortex Bessel beam with the wavelength of 1530 nm has been developed. The polarizer contains 33 layers of SiO2 / Nb2O5 evaporated on a glass substrate using the vacuum electron beam method. The measurement of polarizer characteristics showed the ratio of transmittance of radially- and azimuthally-polarized beams to be 80:1 – 90:1 with the angle of incidence equal to 24.5 – 25°. The transmittance of radially-polarized light was not less than 75%. A radially-polarized zero-order vortex Bessel beam of high optical quality was formed with the help of the developed polarizer and a diffractive axicon.
A new approach is proposed to implement phase contrast Zernike filter with dynamic transparent for phase objects visualization. We investigated the effect of the radius size of the filter at the low and high phase distribution of objects in the input plane to the spatial intensity distribution. A significant increase in contrast is shown when using the proposed dynamic filter. The experimental results of the dynamic phase-contrast filter Zernike are consistent with the numerical simulation.
A new approach is proposed to implement diffractive optical elements (DOEs) for the conversion of the polarization state of beams. The fabricated four-sector polarization converter is experimentally investigated. The orthogonal polarization state of beams in opposite sectors is achieved by selecting a wavelength with a tunable laser. The experimental results of focusing the converted beams are presented.
An approach is proposed to implement diffractive optical elements for the conversion of the polarization state of beams. Calcite crystal etching technology is developed and applied to manufacture a four-sector polarization converter. The fabricated four-sector polarization converter is experimentally investigated. The orthogonal polarization state of beams in opposite sectors is achieved by selecting a wavelength with a tunable laser. The experimental results of focusing the converted beams are consistent with the numerical simulation.
A method is proposed for detecting birefringence of mechanically free parabolic gradient-index lenses based on the astigmatic transformation of the zero-order Bessel beam. The degree of astigmatism can be determined from the intensity distribution of the distorted beam. Similar patterns are also obtained in an experimental study of the passage of a Bessel beam through a quarter-pitch gradient-index lens, which indicates the presence of birefringence of the lens material. Comparison of experimental data and numerical simulation shows the possibility of measuring the optical path difference of no worse than 0.05λ0 between ordinary and extraordinary beams.
New polarization converter for transforming the circulary polarized laser modes into cylindrical vector beams (CVB) including beams of higher orders is proposed. The generation of CVB in birefringent crystals is studied analytically and experimentally in paraxial and non-paraxial regimes. At sharp focusing (in the non-paraxial case) two focuses corresponding ordinary and extraordinary beams are formed along the crystal’s axis. The results are extended to the generation of higher-order radially and azimuthally polarized mode beams. Using the simulation the possibility of fabricating crystal-based devices suitable for application in fiber optics was shown. The results of the experimental study on the generation of cylindrical vector beams in a crystal of Iceland spar agree with the results of the simulation.
The optical system for converting laser beams with circular polarization to cylindrical vector beams on the basis of
anisotropic crystals has been developed. The experimental research of beam formation quality has been carried out on
the both polarization and structural characteristics. The research showed differences in the formation of the azimuthal
and radial polarizations for Gaussian modes and Bessel beams. The boundaries of changes of the optical system
parameters to form different types of polarizations with different amplitude and phase distributions have been identified.
The calculation and simulation of interference polarizer to generate radially polarized light is made. The method is based on converting the conical wavefront passing through the interference polarizer. The multilayer optical coating can be applied on the surface of the axicon. It is shown that in this way we noticeably reduce both the operating angle of incidence and achieve practically significant degree of polarization of the beam generated at much lower energy losses.
KEYWORDS: Axicons, Near field optics, Binary data, Polarization, Diffraction, Near field, Optical components, Near field diffraction, Ions, Electron beam lithography
We analytically and numerically show that by introducing the asymmetry into the axicon design it becomes possible to generate the longitudinal electric field (E-field) component on the optical axis for linearly and circularly polarized incident beams. Binary axicons with high numerical aperture (NA) are fabricated in three configurations – axisymmetric and spiral ones, and bi-axicon – by electron beam lithography. Experimental measurements for the near-field diffraction of most common and easy to implement incident beams – linearly and circularly polarized – are conducted. The experimental results agree with the theoretical analysis.
KEYWORDS: Polarization, Near field scanning optical microscopy, Objectives, Near field, Molecules, Microscopy, Zone plates, Gaussian beams, Fiber optics, Microscopes
We conduct a theoretical and experimental study of the distribution of the electric field components in the focal plane when rotating a zone plate with a π- phase jump placed in the focused beam. By comparison of the theoretical and experimental results, the analysis of the polarization sensitivity of different types of metal-coated aperture probes is conducted. It is demonstrated that with increasing diameter of the non-metal-coated tip part there occurs an essential redistribution of sensitivity in favor of the transverse electric field components and the increase of the probe’s energy throughput. We obtain that the probe response is similar to the transverse component of electric field in the case of Gaussian beam focusing however in the case of Hermite-Gaussian beam focusing the probe response is similar to gradient of electric longitudinal component.
We propose and analyze new polarization converters to transform the linearly polarized laser modes into axially symmetric modes, which show more promise in various applications, as well as generating various inhomogeneously polarized configurations. Designed converters are based on the coherent composition of the modal beams with different amplitude-phased distribution and polarization states. What makes the systems simple and universal is the use of diffractive optical elements (DOEs) to generate required mode patterns with specific space orientation alongside the simultaneous generation of different beams with different transverse mode content, which can be subsequently combined. The numerical modeling of the polarization mode converters has made it possible to analyze its performance and capabilities. The DOEs in question have been designed and fabricated. Natural experiments that demonstrate the generation of vector higher-order cylindrical beams have been conducted.
We report on the fabrication of metallodielectric photonic crystals by means of interference (or holographic) lithography
and subsequent coating by gold nanoparticles. The grating is realized in a SU-8 photoresist using a He-Cd laser of
wavelength 442 nm. The use of the wavelength found within the photoresist low absorption band enables fabricating
structures that are uniform in depth. Parameters of the photoresist exposure and development for obtaining a porous
structure corresponding to an orthorhombic lattice are determined. Coating of photonic crystals by gold nanoparticles is
realized by reduction of chloroauric acid by a number of reductants in a water solution. This research shows that the
combination of interference lithography and chemical coating by metal is attractive for the fabrication of
metallodielectric photonic crystals.
The first results on the use of the hot stamping technique for fabricating a diffraction
grating on the end face of the polycrystalline IR fibers (PIR-fibers) were reported in before. This
paper presents a continuation of the research in this direction. In particular, we look into the
possibility of using the hot stamping technique for fabricating antireflection subwavelength
structures on the end faces of the silver halide PIR-fibers.
Measuring the power distribution among transverse modes of coherent light in optical fibers and excitation of transverse
modes or modal groups in a fiber are of practical significance for development and investigation of fiber lasers, sensors
and fiber communication lines. The feasibility of mode generation in a step-index optical fiber using binary phase
diffractive optical elements (DOEs) is studied. Modes different from the principal mode are selectively excited in the
optical fiber using the binary phase DOEs. It is also reasonable to make a computer simulation of mode excitation to
predict the behavior of optical system. Simulation results prove theoretical derivations on characteristics of mode
excitation. These results are also in a good concordance with experimental ones.
Usage of diffractive optical elements (DOEs) in fiber sensors is rather promising. This work is dedicated to the investigation of dependence of transverse mode spectrum in fibers with the step-like refractive profile on the micro bending value by means of the diffractive optical elements. Description of an experimental setup is provided here as well as methods of the experimental data processing allowing to have accurate measurements of the mode power. Dependence ofthe LP mode power on the fiber micro bending value is received. The received results allow expecting to design fiber sensors with advanced characteristics-dynamic range and accuracy.
An increase in the data-carrying abilities of modern communication systems is a most important scientific and technical challenge, requiring further studies of the physical effects involved. The possibility to increase in the data-carrying abilities of optical communication systems by waveguide transverse modes multiplexing by diffractive optical elements (DOEs) is considered.
Introduction of diffractive optical elements (DOEs) opened the possibilty to control amplitude-phase distribution in the cross-section of laser beam. In fact, by use of DOE one can form the beam with pregiven behaviour during propagation through waveguide medium. The diffractive microrelief can be realized either on the separated substrate or directly on the waveguide surface. This work is devoted to the theoretical and experimental investigation of diffractive microrelief intended for waveguiding beam control. Experimental results of step-like optical waveguide mode excitation and selection by DOE are presented. Different approaches for synthesis of high-efficient DOEs matched with waveguide modes are discussed. The strategy of the search of waveguide mode with amplitude distribution closed to the illuminating beam amplitude distribution is presented. The phase of found mode can be chosen as DOE phase function.
An increase in the data-carrying abilities of modern communication systems is the most important scientific and technical challenge, requiring further studies of the physical effects involved. The possibility to increase in the data-carrying abilities of optical communication systems by waveguide modes (both longitude and transverse) multiplexing by diffractive optical elements (DOEs) is considered.
Analyzing of amplitude-phase characteristics of the laser beam in real-time mode is topical in experimental physics and in a great number of laser applications, such as laser material treatment. The task of analyzing the amplitude-phase beam structure may be treated as that of analyzing the modal composition if this is thought of as both analyzing individual modal powers and intermodal phase shifts. In this paper, the problem is tackled using a special diffractive element (DOE), called MODAN, matched to a group of laser radiation modes. By way of illustration, such an optical element may be implemented as a microrelief applied directly onto an optical material of the laser output window. The experimental results reported indicate that such an approach shows promise.
Novel Diffractive Optical Elements of MODAN-type open up new promising potentialities of solving the tasks of generation, transformation, superposition and subsequent separation again of different transversal laser modes with high efficiency. In we presented for the first time a MODAN capable of transforming a Gaussian TEM00 input beam into a unimodal Gauss-Hermite (GH) (1,0) complex amplitude distribution. Now we present new results achieved by combining several MODANs in one optical set-up: The aim of these investigations is to transform a single TEM00 input laser beam into several partial beams, each of them described by a different unimodal GH (n,m) mode structure. After separately modulating these partial beams in time, and subsequent superposing them to again one beam by means of a conventional beamsplitter, this unified multimode beam is permitted to propagate in space. Following that, an 'analyzing' MODAN is applied to this transversal multimode beam -- a diffractive element which is capable of realizing a spatial modal decomposition of an illuminating beam. For the investigations to be presented here, we restricted ourselves to two unimodal beams and selected as transforming MODANs one element of TEM00-to-GH (1,0) type described and one of TEM00-to-GH (0,1) type. The analyzing MODAN was calculated as a phase-only element using the crossed-gratings method and manufactured with the same technology like the two other elements. Theoretical as well as first experimental results demonstrate promising perspectives for the selected concept.
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