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卷 88, 编号 1 (2024)
Wave Phenomena: Physics and Applications
Differentiation of optical signals using an integrated metal-dielectric-metal structure
摘要
We consider optical properties of integrated metal-dielectric-metal structures embedded in a dielectric slab waveguide and their application to the problems of first- and second-order optical differentiation of the profile of the incident optical beam in reflection. According to the presented numerical simulation results, the investigated structures enable performing the spatial differentiation operation with high quality. The presented results may find application in novel systems for optical information processing and analog optical computing based on integrated nanophotonic structures.
5-10
Research of light diffraction on electrically controlled multiplexed multilayer inhomogeneous holographic diffraction structures based on the photopolymerizing compositions with nematic liquid crystals
摘要
We presented the developed analytical model of optical radiation diffraction on multiplexed multilayer inhomogeneous diffraction structures formed by the holographic method in photopolymerizing compositions with nematic liquid crystals having smooth optical heterogeneity in the thickness of the layers. By numerical calculation, it was shown that when using an applied electric field with different polarities to the diffraction layers, as well as varying the azimuth of the polarization of the reading beam, the angular selectivity of the diffracted beam can be transformed with a significant shift in angular selectivity, which makes it possible to increase the spectral bandwidth by 4 times compared to conventional multilayer diffraction structures.
11-18
Properties of fractal speckle-like structures
摘要
Regarding the use in art therapy and ophthalmology, the properties of fractal speckle-like images are considered. For their construction, both the traditional approach based on the use of two-dimensional fractal functions and a new technique based on the representations of dynamic chaos were used. The important role of the scaling characteristics of the Fourier transforms of fractal light structures is revealed.
19-23
Optical properties of multiplex vortex structures
摘要
As applied to various applied problems, a group of questions on optimizing the characteristics of vortex light beams used in multiplex optical systems is considered. A new method is proposed for the formation of systems of singular beams with small-scale dislocations, which provide a high degree of stability of their structure to the influence of diffraction effects.
24-28
Fine and rough structure of the frequency spectrum of high-power laser diodes during slow degradation
摘要
It is shown that a fine and rough structure can be distinguished in the radiation spectrum of a powerful laser diode. The relationship between the spectrum characteristics and the internal parameters of the laser structure was established and experimentally verified, which was observed during the degradation of the device. The effect of losses in the resonator and coherence of laser radiation on both the fine and rough structure of its radiation spectrum is shown.
29-34
PT-symmetry and radiation structure of high-power laser diodes
摘要
Possible conditions for the application of the quantum formalism of PT-symmetry in solving the wave equation in systems with pseudo-Hermitian Hamiltonian for determining the structure of the optical field and radiation spectra of modern high-power laser diodes are considered. The physical mechanisms affecting the spatial and spectral separation of radiation into separate generation channels are discussed.
35-39
Frequency up-conversion of an even coherent state
摘要
The problem of transferring the state of even coherent states from a low frequency to a high frequency is theoretically considered using a periodically-poled nonlinear crystal. With the help of the Wigner quasi-probability distribution function, a parallel implementation of two nonlinear processes is studied: parametric and sum frequency generation.
40-42
On the influence of intrapulse Raman scattering on the dynamics of pulses in a gradient waveguide
摘要
Based on the method of moments, a system of equations for the parameters of a longitudinal-transverse pulse is obtained. A criterion for the stability of such signals and the characteristic length at which the intrapulse Raman scattering makes the pulse unstable are found.
43-47
Non-perturbative theory of atomic systems interaction with intense laser fields
摘要
A brief description of a consistent non-perturbative approach to study the response of an ensemble of atoms to the action of intense multi-component arbitrary polarized laser field is presented. Its application to the study of the generation of high-order harmonics and generation of terahertz radiation in multi-color laser fields is discussed.
48-53
Accounting for the energy dispersion of free carriers induced by powerful femtosecond laser radiation in dielectrics
摘要
Dynamics of free carriers in the conduction band of dielectrics induced by femtosecond near infrared laser radiation is analyzed. It is stressed the importance of accounting for the energy dispersion term in the Fokker-Planck equation describing such dynamics.
54–59
Generation of optical-terahertz solitons by a few-cycle laser pulse
摘要
The generation of broadband terahertz radiation using an extremely short laser pulse of high intensity is considered. Using numerical simulation of the generalized Yajima-Oikawa system, it is shown that in the generation of an optical-terahertz soliton, in contrast to the quasi-monochromatic case, Kerr nonlinearity plays an important role for a low-period pulse, considering its dispersion.
60-67
On the parametric few-cycle light bullets
摘要
Numerical simulation demonstrates that (2D+1) few-cycle (3–5 oscillations under the envelope) light bullets may form in the medium with quadratic nonlinearity and group velocity anomalous dispersion under conditions of second-harmonic generation. It is shown that as the number of oscillations under the envelope decreases, the parameters of such two-frequency solitons change.
68-73
Formation of quasi unipolar pulses in nonequilibrium magnetized plasma channels
摘要
The possibility of controlling both the spectral and polarization properties of THz pulses propagating in strongly nonequilibrium extended magnetized plasma channels formed by intense UV femtosecond laser pulses in nitrogen (air) is analyzed. The formation of quasiunipolar pulses with a nonzero electric area and a specific state of polarization is discussed. The transformation of such pulses upon leaving the region of a static magnetic field is analyzed.
74-79
Multiphoton ionization in a photonic crystal based on carbon nanotubes under the action of a few cycle optical pulse
摘要
We considered a theoretical model of the interaction of a one-dimensional few cycles optical pulse with a nonlinear medium of semiconductor carbon nanotubes, which has a spatial modulation of the refractive index in the direction of pulse propagation (a one-dimensional photonic crystal). The results of the dependence of the rate of one- and two-photon ionization on the intensity of the short-wavelength pulse are shown. The effect of additional external electric and magnetic fields on the photoionization rate is considered.
80-84
Electron gun with an auto-emission cathode based on carbon nanotubes for a powerful millimeter-range extended interaction klystron
摘要
The possibilities of using auto-emission cathode-grided module in an electron-optical system of extended interaction klystron of the millimeter wavelength range are investigated. The results of a theoretical analysis of the developed design of an electron gun with high compression ratio are presented. The limits of the angular spread of electrons on the grid, which ensures the complete electron beam transmission through the interaction system of the device, are determined.
85-88
Investigation of the third harmonic generation in a high-current relativistic Ka-band gyrotron
摘要
Theoretical and experimental investigations of radiation generation in the frequency multiplication mode at the third harmonic in a high-current Ka-band gyrotron have been carried out. Within the framework of three-dimensional PIC-simulation, it is shown that the nonlinear transformation coefficient in the W-band can reach values of 0.5%. Experimental data on registration of radiation in this range are presented.
89-94
Simulation of electron-optical system for 300 GHz relativistic gyrotron
摘要
Calculations were made for a three-electrode magnetron-injector gun with a thermionic cathode for a relativistic gyrotron in the 300 GHz range, which provides the formation of a helical beam with an energy of 250 keV, a current of 100—300 A, and a pitch factor of 1.1. The possibility of generating radiation with a power of more than 8 MW in a gyrotron with a longitudinally slotted cavity has been shown within the framework of three-dimensional PIC-simulations.
95-99
Characteristics of a distributed location system with an ultra-wideband probing signal
摘要
Using numerical simulations, the characteristics of an ultra-wideband distributed probing system for various network configurations are investigated and its optimal configuration is proposed. It is shown that the range and transverse coordinate resolutions in this case are determined by the characteristics of the probing pulse and can reach 2—3 centimeters, which corresponds to an effective angular resolution of several tens of microradians.
100-106
Broadband rectification of microwave current in magnetic tunnel junctions with perpendicular magnetic anisotropy
摘要
We experimentally studied the effect of broadband rectification of microwave current in magnetic tunnel junctions with perpendicular magnetic anisotropy with using the method of spin-transfer ferromagnetic resonance in a planar external magnetic field. It was found that the parameters of broadband rectification (frequency range, rectified voltage value and the region of existence of the ferromagnetic resonance mode) depend on the size of the sample and its shape. The maximum value of the rectified voltage was on a round elliptical sample of 100×150 nm. At the same time, the widest operating frequency range of approximately 2 GHz was observed on strongly elliptical MTJs with the size of 75×250 nm.
107-111
Phase transitions in rare-earth ferrimagnets with surface anisotropy near the magnetization compensation point
摘要
Theoretical model is proposed for calculating the phase H-T diagrams of a rare-earth ferrimagnet, considering the effects of each of the magnetic sublattices and surface anisotropy. Magnetic phase diagrams are numerically calculated. The presence of surface anisotropy leads to blurring of the second-order phase transition lines between the collinear and angular phases, displacement of the tricritical point, as well as the possibility of the formation of new phase transition lines.
112-118
Estimation of gas saturated sediments parameters in shallow water using vector receiver
摘要
A scheme for estimating parameters of gas-saturated sediments in shallow waters based on signals from moving noise source is proposed and tested on experimental data. Advantages of joint use of information about pressure and vertical component of particle velocity in solving the considered problem are discussed.
119-124
Impact of treatment trajectory on the thermal ablation rate and biological tissue volumetric lesion during irradiation by shock-wave focusing ultrasonic beam
摘要
Thermal ablation rates and the shapes of volumetric biological tissue lesion are compared in a numerical experiment, in which biological tissue is exposed to pulsed periodic shock-wave high intensity focused ultrasound. The comparison is performed across three different irradiation sequences of discrete foci placed uniformly within the target area.
125-130
Сalculation of fields scattered by inhomogeneous area with a large wave size
摘要
A method is proposed for finding acoustic fields scattered by an inhomogeneous area of space with a large wave size. In this case, the RAM of a personal computer is not enough to solve the direct problem at once in the entire study area. Then the area is divided into sub-areas, and the iterative procedure is organized based on problem solution in each individual sub-area.
131-137
Use of geometric properties of three invariants in wave problems of hydrodynamics and electrodynamics
摘要
The theory of deformations is common to the theory of elasticity, hydrodynamics and electrodynamics. The conservation law for the deformation of the control figure contains linear, quadratic and cubic invariants. Passing to the limit of the derivation of the continuity equation destroys the quadratic and cubic invariants in the formula for the volume expansion coefficient. This simplification can lead to the loss of some fluid motion modes. This simplification can lead to the loss of some modes of behavior of electromagnetic fields. A method for taking into account three invariants in the solutions of the equations of hydrodynamics and electrodynamics is presented. For this, wave differential equations of the second and third order in time are used.
138-147
On the threshold value of the vertical vibrations amplitude causing Faraday ripples on the charged surface of a viscous liquid
摘要
The influence of the surface electric charge on the regularities of the formation of Faraday ripples on the horizontal surface of a viscous liquid is studied on the base of the approximation of small-amplitude perturbations. The typical horizontal dimensions of the Faraday ripples are established which is most significantly affected by the surface change density and viscosity.
148-153
Periodic surface disturbances in the concentration-stratified viscous fluid
摘要
The propagation of two-dimensional periodic capillary-gravitational periodic disturbances of a free surface in a viscous uniformly stratified liquid is investigated. Dispersion relations describing periodic surface flows of physical quantities are obtained. It is shown that there are additional flow components that are absent in the model of an ideal fluid. The obtained dispersion relations uniformly converge to the known expressions in the limit transitions.
154-159
Dynamics of brain wave rhythms predicts the speed of cognitive tasks
摘要
We investigated the physiological and behavioral characteristics of children aged 9—10 years during a neurophysiological experiment aimed at performing tasks based on the Sternberg paradigm. A statistical analysis of the stability of wave rhythms as well as a correlation analysis between them and the average reaction time was carried out, based on which a biomarker of the efficiency of the working memory task was found.
160-163
Estimation of the cardiovascular system of Danio rerio embryos using high-frequency ultrasound scanner
摘要
Сердце эмбриона рыбы Danio rerio в возрасте 40—48 ч после оплодотворения было исследовано in vivo с помощью импульсного сканирующего акустического микроскопа в частотном диапазоне 50—100 МГц. Разработанная методика позволяет оценивать параметры сердечной деятельности в течение нескольких часов и наблюдать аномальное поведение сердца, такое как аритмия.
164-168