scholarly journals Propagation and Transformation of Vortexes in Linear and Nonlinear Radio-Photon Systems

Fibers ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 4
Author(s):  
Valery H. Bagmanov ◽  
Albert Kh. Sultanov ◽  
Ivan K. Meshkov ◽  
Azat R. Gizatulin ◽  
Raoul R. Nigmatullin ◽  
...  
Keyword(s):  
Mixing Process ◽  
Modified Model ◽  
Theoretical Substantiation ◽  
Radio Range ◽  
Two Factors ◽  
Optical Domain ◽  
Vortex Beams ◽  
The Difference ◽  
Order Susceptibility ◽  
Topological Charges

The article is devoted to issues related to the propagation and transformation of vortexes in the optical range of frequency. Within the framework of the traditional and modified model of slowly varying envelope approximation (SVEA), the process of converting vortex beams of the optical domain into vortex beams of the terahertz radio range based on nonlinear generation of a difference frequency in a medium with a second-order susceptibility is considered. The modified SVEA splits a slowly varying amplitude into two factors, which makes it possible to more accurately describe the three-wave mixing process. The theoretical substantiation of the rule of vortex beams topological charges conversion is given—the topological charge of the output radio-vortex beam is equal to the difference between the topological charges of the input optical vortex beams. A numerical simulation model of the processes under consideration has been implemented and analyzed.

scholarly journals Propagation and Transformation of Vortexes in Linear and Nonlinear Radio-photon Systems

2021 ◽  
Author(s):  
Valery H. Bagmanov ◽  
Albert Kh. Sultanov ◽  
Ivan K. Meshkov ◽  
Azat R. Gizatulin ◽  
Raoul R. Nigmatullin ◽  
...  
Keyword(s):  
Mixing Process ◽  
Modified Model ◽  
Theoretical Substantiation ◽  
Radio Range ◽  
Two Factors ◽  
Optical Domain ◽  
Vortex Beams ◽  
The Difference ◽  
Order Susceptibility ◽  
Topological Charges

The article is devoted to issues related to the propagation and transformation of vortexes in the optical range of frequency. Within the framework of the traditional and modified model of slowly varying envelope approximation (SVEA), the process of converting vortex beams of the optical domain into vortex beams of the terahertz radio range based on nonlinear generation of a difference frequency in a medium with a second-order susceptibility is considered. The modified SVEA splits a slowly varying amplitude into two factors, which makes it possible to more accurately describe the three-wave mixing process. The theoretical substantiation of the rule of vortex beams topological charges conversion is given – the topological charge of the output radio-vortex beam is equal to the difference between the topological charges of the input optical vortex beams. A numerical simulation model of the processes under consideration has been implemented and analyzed.

scholarly journals Optics-to-THz conversion of vortex beams using nonlinear difference frequency generation

2019 ◽  
Vol 43 (6) ◽  
pp. 983-991
Author(s):  
V.Kh. Bagmanov ◽  
A.Kh. Sultanov ◽  
A.R. Gizatulin ◽  
I.K. Meshkov ◽  
I.A. Kuk ◽  
...  
Keyword(s):  
Topological Charge ◽  
Difference Frequency Generation ◽  
Difference Frequency ◽  
Modified Model ◽  
Theoretical Substantiation ◽  
Vortex Beams ◽  
Frequency Generation ◽  
The Difference ◽  
Order Susceptibility ◽  
Topological Charges

In this paper, using a modified model of slowly varying amplitudes, a process of optics-to-THZ-conversion of vortex beams based on the nonlinear difference frequency generation in a medium with second-order susceptibility is considered. A theoretical substantiation of the law of topological charge conversion of vortex beams is given – the topological charge of the output THz vortex beam is equal to the difference of the topological charges of the input optical vortex beams. A simulation model of the processes under consideration is implemented.

scholarly journals Characteristics of Spiral Patterns Formed by Coaxial Interference between Two Vortex Beams with Different Radii of Wavefront Curvatures

Photonics ◽  
2021 ◽  
Vol 8 (9) ◽  
pp. 393
Author(s):  
Jingbo Ma ◽  
Peng Li ◽  
Yuzong Gu
Keyword(s):  
Theoretical Model ◽  
Phase Difference ◽  
Spherical Wave ◽  
Spiral Pattern ◽  
Absolute Value ◽  
The Core ◽  
Vortex Beams ◽  
The Difference ◽  
Set Up ◽  
Topological Charges

Spiral pattern is formed for coaxial interference between two vortex beams with different radii of wavefront curvatures and different topological charges (TCs). A theoretical model considering various parameters (such as phase difference, radius of wavefront curvature, and TCs) is established to predict all kinds of interference patterns. An improved Mach-Zehnder interferometer is set up in an experiment to generate different kinds of spiral patterns and verify the theoretical model. The number of spiral lobes is determined by the absolute value of TCs’ difference between two vortex beams, and the twist direction relates to the sign of TCs’ difference and the difference of reciprocals for the radii of wavefront curvature, clockwise for the same sign, and counterclockwise for the opposite signs. The twist direction of the spiral pattern reverses and the lobes direction near the core of the pattern changes obviously when the spherical wave changes from convergence to divergence.

Slow Down You’re Moving Too Fast

2015 ◽  
Vol 27 (2) ◽  
pp. 53-63 ◽  
Author(s):  
Annie Lang ◽  
Nancy Schwartz ◽  
Sharon Mayell
Keyword(s):  
Older Adults ◽  
Cognitive Aging ◽  
Attention And Memory ◽  
Younger Adults ◽  
Media Messages ◽  
Two Factors ◽  
The Difference

The study reported here compared how younger and older adults processed the same set of media messages which were selected to vary on two factors, arousing content and valence. Results showed that older and younger adults had similar arousal responses but different patterns of attention and memory. Older adults paid more attention to all messages than did younger adults. However, this attention did not translate into greater memory. Older and younger adults had similar levels of memory for slow-paced messages, but younger adults outperformed older adults significantly as pacing increased, and the difference was larger for arousing compared with calm messages. The differences found are in line with predictions made based on the cognitive-aging literature.

scholarly journals High-Efficiency Spin-Related Vortex Metalenses

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1485
Author(s):  
Wei Wang ◽  
Ruikang Zhao ◽  
Shilong Chang ◽  
Jing Li ◽  
Yan Shi ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Orbital Angular Momentum ◽  
Topological Charge ◽  
High Efficiency ◽  
Infrared Band ◽  
Mid Infrared ◽  
Integrated Devices ◽  
Vortex Beams ◽  
Topological Charges

In this paper, one spin-selected vortex metalens composed of silicon nanobricks is designed and numerically investigated at the mid-infrared band, which can produce vortex beams with different topological charges and achieve different spin lights simultaneously. Another type of spin-independent vortex metalens is also designed, which can focus the vortex beams with the same topological charge at the same position for different spin lights, respectively. Both of the two vortex metalenses can achieve high-efficiency focusing for different spin lights. In addition, the spin-to-orbital angular momentum conversion through the vortex metalens is also discussed in detail. Our work facilitates the establishment of high-efficiency spin-related integrated devices, which is significant for the development of vortex optics and spin optics.

scholarly journals An experimental and theoretical investigation of diffusion in a two-phase alloy

1948 ◽  
Vol 192 (1031) ◽  
pp. 575-592 ◽  
Keyword(s):  
Free Energy ◽  
Single Phase ◽  
Phase State ◽  
Theoretical Treatment ◽  
Research Association ◽  
Essential Difference ◽  
Two Phase ◽  
Two Factors ◽  
Order Of Magnitude ◽  
The Difference

The present paper describes an investigation of diffusion in the solid state. Previous experimental work has been confined to the case in which the free energy of a mixture is a minimum for the single-phase state, and diffusion decreases local differences of concentration. This may be called ‘diffusion downhill’. However, it is possible for the free energy to be a minimum for the two-phase state; diffusion may then increase differences of concentration; and so may be called ‘diffusion uphill’. Becker (1937) has proposed a simple theoretical treatment of these two types of diffusion in a binary alloy. The present paper describes an experimental test of this theory, using the unusual properties of the alloy Cu 4 FeNi 3 . This alloy is single phase above 800° C and two-phase at lower temperatures, both the phases being face-centred cubic; the essential difference between the two phases is their content of copper. On dissociating from one phase into two the alloy develops a series of intermediate structures showing striking X-ray patterns which are very sensitive to changes of structure. It was found possible to utilize these results for a quantitative study of diffusion ‘uphill’ and ‘downhill’ in the alloy. The experimental results, which can be expressed very simply, are in fair agreement with conclusions drawn from Becker’s theory. It was found that Fick’s equation, dc / dt = D d2c / dx2 , can, within the limits of error, be applied in all cases, with the modification that c denotes the difference of the measured copper concentration from its equilibrium value. The theory postulates that D is the product of two factors, of which one is D 0f the coefficient of diffusion that would be measured if the alloy were an ideal solid solution. The theory is able to calculate D/D 0 , if only in first approximation, and the experiments confirm this calculation. It was found that in most cases the speed of diffusion—‘uphill’ or ‘downhill’—has the order of magnitude of D 0 . * Now with British Electrical Research Association.

Direct generation of optical vortex beams with tunable topological charges up to 18th using an axicon

2021 ◽  
Vol 143 ◽  
pp. 107339
Author(s):  
Ke Li ◽  
Kaifei Tang ◽  
Da Lin ◽  
Jing Wang ◽  
Bingxuan Li ◽  
...  
Keyword(s):  
Optical Vortex ◽  
Vortex Beams ◽  
Direct Generation ◽  
Topological Charges

scholarly journals Arbitrary polarization conversion for pure vortex generation with a single metasurface

Nanophotonics ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 727-732
Author(s):  
Marco Piccardo ◽  
Antonio Ambrosio
Keyword(s):  
Angular Momentum ◽  
Polarization Conversion ◽  
Vortex Beam ◽  
Vortex Generation ◽  
Optical Elements ◽  
Amplitude Control ◽  
Cavity Resonators ◽  
Vortex Beams ◽  
Topological Charges ◽  
Selection Of

AbstractThe purity of an optical vortex beam depends on the spread of its energy among different azimuthal and radial modes, also known as $\ell $- and p-modes. The smaller the spread, the higher the vortex purity and more efficient its creation and detection. There are several methods to generate vortex beams with well-defined orbital angular momentum, but only few exist allowing selection of a pure radial mode. These typically consist of many optical elements with rather complex arrangements, including active cavity resonators. Here, we show that it is possible to generate pure vortex beams using a single metasurface plate—called p-plate as it controls radial modes—in combination with a polarizer. We generalize an existing theory of independent phase and amplitude control with birefringent nanopillars considering arbitrary input polarization states. The high purity, sizeable creation efficiency, and impassable compactness make the presented approach a powerful complex amplitude modulation tool for pure vortex generation, even in the case of large topological charges.

Propagation Characteristics of Vortex Beam Using Visualization Analysis in Free Space

2021 ◽  
Vol 16 (5) ◽  
pp. 838-843
Author(s):  
Yan Zhang ◽  
Minru Hao ◽  
Min Shao ◽  
Yunzhe Zhang
Keyword(s):  
Optical Communication ◽  
Free Space ◽  
Simulation Analysis ◽  
Propagation Distance ◽  
Momentum Density ◽  
Linear Momentum ◽  
Propagation Characteristics ◽  
Transverse Profile ◽  
Vortex Beams ◽  
Topological Charges

We theoretically analyze the linear momentum density and orbital angular momentum (OAM) propagation characteristics of Gaussian vortex beams in free space, and perform detailed numerical simulation analysis of the linear momentum density and OAM propagation characteristics. Further, we study the variation of the propagation characteristics with different topological charges. In addition, we also analyzed the position of momentum in the transverse profile, where the momentum density of the spot will be broadened with propagation distance. This study can provide guidance for using vortex beams in optical communication and manipulation.

The opposite and antagonistic effects of the closely related POU family transcription factors Brn-3a and Brn-3b on the activity of a target promoter are dependent on differences in the POU domain

1994 ◽  
Vol 14 (10) ◽  
pp. 6907-6914
Author(s):  
P J Morris ◽  
T Theil ◽  
C J Ring ◽  
K A Lillycrop ◽  
T Moroy ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Promoter Activity ◽  
Group Iv ◽  
Promoter Activation ◽  
Antagonistic Effects ◽  
Pou Domain ◽  
Close Relationship ◽  
Two Factors ◽  
The Difference ◽  
Target Promoter

The Brn-3a, Brn-3b, and Brn-3c POU family transcription factors are closely related to one another and are members of the group IV subfamily of POU factors. Here we show that despite this close relationship, the factors have different effects on the activity of a target promoter: Brn-3a and Brn-3c stimulate the promoter whereas Brn-3b represses it. Moreover, Brn-3b can antagonize the stimulatory effect of Brn-3a on promoter activity and can also inhibit promoter activation by the Oct-2.1 POU factor. The difference in the transactivation activities of Brn-3a and Brn-3b is dependent upon the C-terminal region containing the POU domain of the two proteins, since exchange of this domain between the two factors converts Brn-3a into a repressor and Brn-3b into an activator.

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