Phase Incursion Research Articles

Computer model of a signal filtering device for a monitoring earth station

Satellite communication systems have an advantage over other communication systems, as they have a large coverage of the territory. The Earth station can be located anywhere in this territory and can be either a legitimate user or a satellite pirate (an illegitimate user). The developers are faced with the task of determining the coordinates of an illegitimate user illegally occupying a frequency resource. The article proposes a block diagram of a signal filtering device, which is part of a device for determining the coordinates of an illegitimate user, a monitoring Earth station. The purpose, requirements and main task of each composite block of the filtration device are defined. The search and analysis of analog filters and signal filtering methods was carried out. In the MatLab Simulink software environment, a computer model of a signal filtering device has been developed according to a block diagram with the possibility of determining the phase run, as well as the settings of the filtering device blocks are disclosed, which can be adjusted during the study of the model. For the bandpass filters included in the filtering device, the phase frequency characteristics of the phase change of the received signal on the frequency of this signal are constructed. A phase lock loop system has been formed with the possibility of changing its parameters. Calculations of the phase incursion through the elements of the filtration device are made.

Boundary conditions for the order parameter and the proximity influenced internal phase differences in double superconducting junctions

This paper gives an overview of the unconventional dependence of internal phase differences on the external phase difference in superconductor–normal metal–superconductor (SINIS) and superconductor–superconductor–superconductor (SISIS) tunnel double junctions. The results are obtained within the Ginzburg–Landau (GL) approach that includes boundary conditions for the superconductor order parameter in the presence of a Josephson coupling through interfaces. The boundary conditions are derived within the GL theory and substantiated microscopically. The absence of the one-to-one correspondence between external ϕ and internal χ1,2 phase differences in the junctions is shown to occur in two qualitatively different ways, both of which result in the range of χ1,2 reduced and prevent the 4π-periodic current–phase relation j=jcsinϕ2. In SINIS junctions, the effect of the supercurrent–induced phase incursion φ between the end faces of the central electrode of mesoscopic length L can play a crucial role. In SISIS junctions, there occurs the regime of interchanging modes, which is modified as L decreases. The proximity and pair breaking effects in the double junctions with closely spaced interfaces are addressed.

Influence of Nanoemulsion Droplet Size of Removing Water Blocking Damage in Tight Gas Reservoir

During the production process, water phase incursion into the reservoir causes water blocking damage and seriously affects the production of tight gas reservoirs. Recently, nanoemulsions have been used as highly effective water blocking removing agents in the field, but their mechanism is still unclear. In this research, a series of nanoemulsions with different droplet sizes were synthesized, and their water blocking removing performance was intensively investigated. To begin, the relationship between the droplet size and the chemical composition of the nanoemulsion was determined by dynamic light scattering. Second, the influence of the nanoemulsion droplet size on the surface tension and the contact angle experiments was studied. Finally, NMR and permeability recovery experiments were used to study the relationship between the droplet size and the water locking removing effect of the nanoemulsions. Simultaneously, the surfactant release process was investigated using the static adsorption curves of the nanoemulsions. The experimental results show that the droplet size of nanoemulsion has an exponential relationship with the oil phase content. The surface tension decreases with the increase in droplet size, but the wetting reversal effect decreases with the increase in droplet size. The nanoemulsion with an oil phase content of 5 wt.% has the best water locking removing effect, and the permeability recovery value of the core reaches 59.54%. The adsorption control of the nanoemulsion on the surfactant is the key to its water blocking removing ability. This comprehensive study shows that the nanoemulsion with an oil phase content of 5 wt.% has optimum adsorption control capability. Thus, it can be used as a promising candidate for removing water blocking in tight gas reservoirs.

Autobalanced spectroscopy of CPT resonance in an optically dense atomic ensemble

We investigate the influence of optical thickness on the coherent population trapping (CPT) resonance interrogated by the autobalanced Ramsey method as well as by the method of combined error signals (CESs). We analyze sensitivity of the CPT resonance to the light shift of the etalon transition for the microwave quantum frequency standards based on cold or hot atomic ensembles. When the CPT resonance is excited, two-frequency laser radiation can be significantly absorbed at the atomic transitions of the optical range. The effects of absorption and phase incursion lead to additional shift of the reference resonance. This is an additional factor that degrades the accuracy of the frequency standards because this additional shift can vary with intensity and temperature fluctuations. It was shown that the CES method is more robust in an optically dense medium than is the autobalanced Ramsey method, but it also undergoes the light shift. We found that by choosing the normalization factor of the CES method it is possible to suppress the light shift for a certain density of the medium or suppress its sensitivity to temperature fluctuations.

Principles of constructing gyroscopes based on photonic crystal (band-gap) fibers

The gyroscope is a device that makes it possible to measure the change in the orientation angles associated rotation of the body relative to an inertial coordinate system. Photonic crystal fiber gyroscopes are a kind of optical gyroscopes that offer many new features beyond that conventional fiber optic gyroscopes can offer. In any case, the properties of the optical fiber can play a large role in determining the characteristics of the gyroscope. The principle of operation of most optical gyroscopes is based on the Sagnac effect or the Sagnac interferometer, the essence of which is as follows. If two light waves propagate in a closed optical circuit in opposite directions, then in the case of an immovable circuit, the phase incursions of both waves that have passed the entire circuit in opposite directions will be the same. When the contour rotates around an axis normal to the contour plane, the phase incursions of the waves become unequal, and their difference in the general case will be proportional to the angular velocity of the contour rotation, the area covered by the contour, and the frequency of the electromagnetic wave (EMW). Since the area and frequency of the EMW remain unchanged during the operation of the gyroscope, the phase shift will be proportional only to the angular velocity. The use of photonic crystal fiber to increase the sensitivity is very promising; it significantly reduces the drift through thermal polarization, resistance, and the Kerr effect. This article suggests the use of photonic-crystal (hollow-core) fiber in optical gyroscope instead of conventional fibers.

Polarization features of asymmetric TE and TM vortex modes

This study is devoted to a new section in the field of singular optics-to beams carrying a fractional topological charge. A feature of this type of beams is structural instability, and with the slightest external perturbation, these beams form arrays of optical vortices. These vortices can be connected and, as it were, form an integral picture, or disintegrate due to the fact that during the propagation each of the vortices receives an additional phase incursion. These studies were based on a theoretical calculation and experimental study of the vector structure of beams transporting optical vortices with a fractional topological charge and the proof of the process of forming asymmetric TE (transversely electrical) and TM (transverse magnetic) modes in free space, and the study of the features of their “thin” vector structures in free space.

Nonconservation of Topological Charge and Cusps in a One-Dimensional Laser Scheme.

An analysis was made of the field structures in a coaxial laser with fast saturable absorption. In such an efficiently one-dimensional scheme, the integer topological index (charge) naturally arises: the phase incursion of the field envelope when bypassing the aperture, divided by 2π. The topological charge is the winding number for the phase curve introduced for the electric field envelope with increase of the coordinate for fixed time. In the framework of the generalized Ginzburg-Landau equation, shown are finite numbers of plane-wave modes, stable with respect to weak perturbations, and solitonlike modes with inhomogeneous intensity distributions and different topological charge. It was found that the topological charge could change during transient to steady state. The events of these changes alternate with formation of cusps of the phase curve occurring when extrema of the field intensity and phase coincide.

The Effect of Diffraction on a Pulse of Squeezed Light in the Protocol of a Multimode Resonant Quantum Memory Based on a Thermal Atomic Ensemble

The effect of diffraction on the conservation of the quantum state of a quadrature-squeezed light pulse in an ensemble of thermal atoms for a collinear configuration of light fields has been considered. The motion of atoms leads to the fact that when both the signal and control fields propagate in the same direction as when writing, there is an uncompensated phase incursion even in the case of forward reading. This phase incursion leads to the fact that the squeezed quadrature of the light pulse is mixed with a stretched one. As a result, the pulse squeezing can decrease significantly. The analyses of the effect of diffraction for different configurations of the multimode resonant quantum memory protocol has been performed and the ways to reduce this effect to a possible minimum have been found.

Optical Aharonov—Bohm Effect

A variant of the experiment to observe the optical Aharonov—Bohm effect has been discussed. In the experiment, a unipolar subcycle light pulse has been proposed as a source of the vector potential acting on electrons and having zero electric field strength in the region of a nonzero vector potential. Such a relation between the field and potential appears because the unipolar pulse has a nonzero electric area. An unusual situation where the fact of the passage of the pulse in one of the arms of two-beam interferometer is stored for a very long time after the passage and can be recorded in a two-beam electronic interferometer by a shift of fringes has been discussed. Detailed analysis of the phase shift under the influence of the vector potential created by the inhomogeneous unipolar pulse removes this contradiction and shows the equality of phase incursions in both arms that is unobvious at first glance.

Effect of elastic anisotropy on thermally induced distortions of a laser beam in single cubic syngony crystals with radial cooling. Part I

We have studied thermally induced distortions of a beam in single cubic syngony crystals of all symmetry groups with an anisotropic elastic stiffness tensor. The arithmetic mean and the difference between the thermally induced phase incursions of eigenpolarisations, as well as the angle of incidence of these polarisations, are calculated for a long rod and a thin disk with radial cooling under uniform volume pumping of the active element. The position of the specific crystal orientations unrelated to its symmetry elements is investigated. The effective values of the thermo-optical constant Q in two specific orientations, as well as the thermo-optical constant P in an arbitrary orientation, are found.

Methods for Determining the Angular Coordinates and Locations of Radio Sources in Unmanned Monitoring Systems and Experimental Estimates of the Accuracy of these Parameters

Methods have been developed for measuring angular coordinates and determining the location of radio emission sources using a panoramic digital direction finding detector located on board an aircraft-type unmanned aerial vehicle. The angular coordinates of the objects were measured by the phase method using the fast Fourier transform and synchronous spectral analysis of signals in the receiving channels while eliminating the ambiguity of the measurements of phase incursions by finding their multiplicity indices. The methodology for determining the location of radio emission sources is based on a rational choice of positions for measuring the directions of arrival of signals at various points on the flight path of an unmanned aerial vehicle according to the criterion of the minimum standard deviations of the source location estimates. The accuracy of measuring the angular coordinates and determining the location of objects in the conditions of a radio measuring range is analyzed. The measurements were performed at frequencies at which the level of background radio emissions is minimal for the operating frequency range of the detector-direction finder and does not lead to the appearance of abnormal errors. When determining the location of radio emission sources, the movement of an unmanned aerial vehicle with a direction-finding detector on board was carried out in an arc with a maximum notch angle of the bearing of 120° and in a spiral when setting directional angles in the turning points of the route according to the criterion of minimizing the dispersion of position determination. It was found that when calculating the phase incursions of signals in the frequency range 30–3000 MHz, the error in measuring the angular coordinates of radio sources is within 3.3–4.9°; for a signal-to-noise ratio 15 dB at the receiver input, the accuracy of the experimental estimate of determining their location is 2.2–13.8% of the range. Detector-direction finders of signals placed on unmanned carriers are used to monitor the electronic environment. Information on the angular coordinates and location of radio emission sources, invariant to changes in their operating modes and parameters of emitted signals, is used for spatial selection and recognition of objects.

Investigation of the Influence of the Earth Ionosphere on the Radio Wave Propagation in the High-Frequency Range

The features of the influence of the Earth ionosphere on the radio wave propagation at the frequencies 200—1200 MHz are considered by the bicharacteristic method. The phase incursion and refraction errors are investigated. The values of the Faraday rotation angle depending on the mutual orientation of the ray trajectories and the vector of the intensity of the external magnetic field are estimated.

Phase relations in superconductor–normal metal–superconductor tunnel junctions

The phase difference $\phi$, between the superconducting terminals in superconductor-normal metal-superconductor tunnel junctions (SINIS), incorporates the phase differences $\chi_{1,2}$ across thin interfaces of constituent $SIN$ junctions and the phase incursion $\varphi$ between the side faces of the central electrode of length $L$. It is demonstrated here that $\chi_{1,2}$ pass through over their proximity-reduced domain twice, there and back, while $\phi$ changes over the single period. Two corresponding solutions, that describe the double-valued order-parameter dependence on $\chi_{1,2}$, jointly form the single-valued dependence on $\phi$, operating in two adjoining regions of $\phi$. The phase incursion $\varphi$ plays a crucial role in creating such a behavior. The current-phase relation $j(\phi,L)$ is composed of the two solutions and, at a fixed small $L$, is characterized by the phase-dependent effective transmission coefficient.

Relativistic Reductions in Precision Measurements of the Earth’s Gravitational Field Using Low-Orbit Spacecraft

The advancement of space technology opens new perspectives in developing high-resolution models of the Earth’s gravitational field. The use of a precision laser interferometric system requires taking relativistic effects in the inter-satellite ranging within the satellite constellation into account. The main quantity measured by the laser system is the phase incursion of the laser beam when passing a double one-way range between the satellites. A solution for the relativistic phase is obtained that considers not only the usual Shapiro term but also the contribution of the quadrupole term to distributions of the Earth’s mass, the Earth’s spin, and tidal gravitational fields caused by the gravitational potentials of the outer bodies of the Solar System. Relativistic reduction terms are estimated at the accuracy level of ∼1 nm, which fully satisfies the accuracy of precision measurements in the two-spacecraft formation. It will be necessary to take the relativistic effects of the next order of smallness into account in the next-generation gravitational twin missions.

Achromatic complex holograms for laser mode conversion.

While conventional complex phase masks are chromatic, we present an achromatic holographic phase mask capable of performing optical beam transformations in a spectral range exceeding 1000 nm. The system consists of a holographic phase mask fabricated by encoding the desired phase profiles into volume Bragg gratings, inserted in between two surface gratings. This device automatically adjusts each spectral component diffracted by the surface grating to the Bragg angle of the volume Bragg grating and equalizes phase incursion for all diffracted wavelengths. Transverse mode conversion is demonstrated and compared with theory for multiple narrow line laser sources operating from 488 to 1550 nm and for a broadband femtosecond source.

High-sensitive absorption measurement in transparent isotropic dielectrics with time-resolved photothermal common-path interferometry.

We propose a time-resolved photothermal common-path interferometry scheme at fast heating in the absence of heat diffusion and employ it to measure absorption in Suprasil 311 silica glass (2.8·10-6 cm-1) at a wavelength of 1071nm and continual absorption in laboratory air (2.9·10-8 cm-1) for a signal-to-noise ratio of 100/1. The absorption was measured at a thermally induced phase incursion of less than 0.1rad in a heating beam, which guaranteed correct calibration. To calibrate this scheme, we developed a theory of diffraction on deformations taking into account the stresses arising in an inhomogeneous temperature field. This allowed us to use a standard glass K8 for calibration. The low level of noise and time resolution of pulsed signals allowed the distinguishing of the contributions of Kerr and striction nonlinearities to absorption measurements in Suprasil 311 silica glass and enabled the observance of the time evolution of strictional deformations. Additionally, an anomalous temporal development of the absorption of broadband laser radiation in atmospheric air at 2.9·10-8 cm-1 has been revealed.

Vortex beams with zero orbital angular momentum and non-zero topological charge

We study the field structure of the vortex beam generated via coherent fiber-array where beamlets are arranged along a circle. Each beamlet is an aperture-bounded Gaussian beam emerging from fiber output with constant phase. The phase shift between neighbor beamlets is the same, and the total phase incursion along the circle is equal to 2πl (l is integer). The total orbital angular momentum of the beam is equal to zero for any propagation distance and arbitrary l. We show that the central part of the far field corresponds to an optical vortex with the orbital angular momentum and the topological charge equal to l (l < N/3, N is the number of beamlets). The dependencies of the orbital angular momentum of the vortex beam on the receiving aperture size and the propagation distance are analyzed.

Measuring transducer of angular displacements using phase raids of the surface acoustic waves electric field

The phase method for angular displacement unambiguous measurement based on the use of surface acoustic waves (SAW) devices is proposed and theoretically grounded.To eliminate any ambiguity of phase measurements, the construction of acousto-electronic angular displacement transducer using phase incursion of several SAW on the surface of the piezoelectric circular waveguide at different frequencies is proposed. The information parameters that determine the position of SAW receiver are measured at these frequencies.The rating of potential metrological parameters of the 3-frequency angular displacement transducer in the range 0…..360 degrees with the formation of precise, intermediate and rough measurement scales is carried out. The use of phase incursion on the surface of the piezoelectric waveguide electric field of three SAW at different frequencies taking by moving SAW receiver allows to form precise, intermediate and rough measurement scales in accordance with 11, 6 and 5 binary digits representing the measurement results.The experimental test results of models of a 3-frequency generator block, an amplifying-selective block and a 3-frequencies angular displacement transducer containing circular piezoelectric waveguide with a radius of 15 mm based on zinc oxide-fused quartz structure over which displaces a circular sectional SAW receiver are presented. The amplitude of the SAW receiver output signal varies exponentially depending on a gap between the piezoelectric waveguide surface and SAW receiver. It requires high precision of transducer manufacturing to ensure parallel to the acoustic line surface movement of receiver thus eliminating the influence of the phase velocity dispersion of the surface acoustic wave as a result of the SAW receiver electric field perturbation on the accuracy of measurements. Grading characteristics of angular displacement transducer are linear. The coefficients of angular displacement transformation on the precise scales are 0.54, 0.55 and 0.56 electric degrees/arcsec in the central frequencies of 69.52, 70.62 and 71.69 MHz. At the same time, the resolution and angular displacements measurement error on the precise scale are respectively less than 0.5 arcsec and 1.5 arcsec.The test results of model based on piezoelectric waveguide of zinc oxide-fused quartz structure confirm the possibility of creating highly sensitive angular displacements transducers with a resolution and accuracy properties that are close to the parameters of inductosyns, photoelectric transducers and laser interferometers. However, it may have considerably less weight and dimensions, cost and complexity of construction.Ref. 20, fig.6.

Third-order-nonlinear effects in single crystals with arbitrary orientation and in ceramics

The influence of cubic crystal orientation on the generation of cross-polarization, self-phase modulation, and laser beam self-focusing is investigated. The orientations at which these effects are maximal and minimal have been found. The qualitative and quantitative difference of these effects in ceramics from those in single crystals and glass has been determined. Random small-scale (of order grain size) spatial modulation of laser beam polarization and phase has been predicted. This effect has no analogs in glasses or in single crystals. It is shown that, from the viewpoint of nonlinear phase incursion average over beam cross-section, ceramics is equivalent to glass whose nonlinearity is determined by a combination of the elements of ceramics tensor χ(3).

Measurement of acoustic wave phase velocity by Fourier method in gas-liquid medium

Results of measuring the phase velocity of weakly nonlinear waves in a gas-liquid mixture by the Fourier method are presented. The method is based on expansion of time signals, taken from two closely spaced pressure gages in propagation of a single finite pressure pulse, into Fourier series and calculation of the phase shift over the entire frequency series. The method was previously tested in a numerical experiment with the use of the known Korteweg–de Vries equation model. The results of phase velocity measurements show that the method is in good agreement with the theory in a frequency range where the phase incursion is under 2π. The proposed method makes it possible to reconstruct all parameters of polydisperse gas-liquid medium, including those of Landau attenuation analog, by the frequency dependence of the measured phase velocity.