scholarly journals Study of Superoscillating Functions Application to Overcome the Diffraction Limit with Suppressed Sidelobes

Optics ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 155-168
Author(s):  
Svetlana N. Khonina ◽  
Ekaterina D. Ponomareva ◽  
Muhammad A. Butt
Keyword(s):  
Numerical Study ◽  
Near Field ◽  
Plane Waves ◽  
Spot Size ◽  
Diffraction Limit ◽  
Field Zone ◽  
Focal Spot Size ◽  
One Dimensional ◽  
Spatial Frequencies ◽  
Superoscillating Functions

The problem of overcoming the diffraction limit does not have an unambiguously advantageous solution because of the competing nature of different beams’ parameters, such as the focal spot size, energy efficiency, and sidelobe level. The possibility to overcome the diffraction limit with suppressed sidelobes out of the near-field zone using superoscillating functions was investigated in detail. Superoscillation is a phenomenon in which a superposition of harmonic functions contains higher spatial frequencies than any of the terms in the superposition. Two types of superoscillating one-dimensional signals were considered, and simulation of their propagation in the near diffraction zone based on plane waves expansion was performed. A comparative numerical study showed the possibility of overcoming the diffraction limit with a reduced level of sidelobes at a certain distance outside the zone of evanescent waves.

scholarly journals Exact eigenstates of a nanometric paraboloidal emitter and field emission quantities

2018 ◽  
Vol 474 (2214) ◽  
pp. 20170692 ◽  
Author(s):  
A. Chatziafratis ◽  
G. Fikioris ◽  
J. P. Xanthakis
Keyword(s):  
Schrödinger Equation ◽  
Field Emission ◽  
Schrodinger Equation ◽  
Near Field ◽  
Plane Waves ◽  
Spot Size ◽  
Emission Angle ◽  
Electron Velocity ◽  
Cartesian Geometry ◽  
Tip Radius

The progress in field emission theory from its initial Fowler–Nordheim form is centred on the transmission coefficient. For the supply (of electrons) function one still uses the constant value due to a supply of plane-waves states. However, for emitting tips of apex radius of 1–5 nm this is highly questionable. To address this issue, we have solved the Schrödinger equation in a sharp paraboloidally shaped quantum box. The Schrödinger equation is separable in the rotationally parabolic coordinate system and we hence obtain the exact eigenstates of the system. Significant differences from the usual Cartesian geometry are obtained. (1) Both the normally incident and parallel electron fluxes are functions of the angle to the emitter axis and affect the emission angle. (2) The WKB approximation fails for this system. (3) The eigenfunctions of the nanoemitter form a continuum only in one dimension while complete discretization occurs in the other two directions. (4) The parallel electron velocity vanishes at the apex which may explain the recent spot-size measurements in near-field scanning electron microscopy. (5) Competing effects are found as the tip radius decreases to 1 nm: The electric field increases but the total supply function decreases so that possibly an optimum radius exists.

scholarly journals Mesoscale Acoustical Cylindrical Superlens

2018 ◽  
Vol 155 ◽  
pp. 01029 ◽  
Author(s):  
Igor Minin ◽  
Oleg Minin
Keyword(s):  
Wave Scattering ◽  
Near Field ◽  
Elastic Solid ◽  
Diffraction Limit ◽  
Solid Particles ◽  
Acoustic Metamaterials ◽  
Field Zone ◽  
Sharp Focusing ◽  
Plane Wave Scattering ◽  
First Time

We demonstrate experimentally for the first time the acoustojet (acoustic jets) formed from acoustic plane wave scattering by a penetrable cylindrical particle with dimensions of several wavelengths. It acts as a superlens with subwavelength localization of acoustical wave. During the scattering by elastic solid particles, additional internal shear waves are excited due to modes conversion. This mechanism allows achieving sharp focusing in the near-field zone. Such mesoscale single particle cylindrical lens may be considered as acoustic metamaterials free superlenses with resolution beyond the diffraction limit.

SU-D-134-02: Selection of Magnification and Focal Spot Size for Optimizing GMTF for Object Specific Spatial Frequencies

2013 ◽  
Vol 40 (6Part3) ◽  
pp. 112-112
Author(s):  
V Singh ◽  
A Jain ◽  
S Setlur Nagesh ◽  
D Bednarek ◽  
S Rudin
Keyword(s):  
Focal Spot ◽  
Spot Size ◽  
Focal Spot Size ◽  
Spatial Frequencies ◽  
Selection Of

Intensity of Diffraction of Laser Irradiating a Microparticle in Nanostructure Processing

2009 ◽  
Vol 83-86 ◽  
pp. 1282-1287
Author(s):  
Ching Yen Ho ◽  
Mao Yu Wen ◽  
C. Ma
Keyword(s):  
Electromagnetic Wave ◽  
Near Field ◽  
Wave Theory ◽  
Spot Size ◽  
Diffraction Limit ◽  
Materials Processing ◽  
Small Aperture ◽  
Laser Technology ◽  
Field Techniques ◽  
20 Nm

Traditional materials processing in the nanometer range using laser technology is very difficult with conventional optics due to the diffraction limit of the beam wavelength, a near-field technology has been developed to circumvent the diffraction limit, permitting the spot size to be reduced down to 20 nm. In most near-field techniques, this technology is achieved by placing a small aperture or microparticle between the sample and the light source. Therefore this paper will analytically investigate the profile of the intensity for diffraction of laser irradiating an aperture or microparticle in nanostructure processing. Classical electromagnetic wave theory is employed to calculate the intensity for diffraction of laser irradiating a microparticle or aperture. The results will reveal the differences between an aperture and micoparticle for diffraction of laser. The effect of laser parameters on the intensity and distribution of diffraction will be also discussed.

scholarly journals The investigation of the features of focusing vortex super-Gaussian beams with a variable-height diffractive axicon

2021 ◽  
Vol 45 (2) ◽  
pp. 214-221
Author(s):  
D.A. Savelyev
Keyword(s):  
Gaussian Beam ◽  
Circular Polarization ◽  
Focal Spot ◽  
Near Field ◽  
Optical Element ◽  
Spot Size ◽  
Minimum Size ◽  
Focal Spot Size ◽  
Diffractive Axicon ◽  
Difference Time

Spatial intensity distributions of the Laguerre-superGauss modes (1,0) as well as a super-Gaussian beam with radial and circular polarization were investigated versus changes in the height of a diffractive axicon. The height of the relief of the optical element varied from 0.25λ to 3λ. The modeling by a finite-difference time-domain method showed that variations in the height of the diffractive axicon significantly affect the diffraction pattern in the near field of the axicon. The smallest focal spot size for a super-Gaussian beam was obtained for radial polarization at a height equal to two wavelengths. The minimum size of the focal spot for the Laguerre-superGauss mode (1,0) was obtained for circular "–" polarization with an element height equal to a quarter of the wavelength.

Principles of regular-shaped radome antennas study with a spherical scanner

2020 ◽  
pp. 14-21 ◽  
Author(s):  
A. V. Kirpanev ◽  
N. A. Kirpanev
Keyword(s):  
Near Field ◽  
Plane Waves ◽  
Single Layer ◽  
Surface Shape ◽  
Complex Coefficient ◽  
Spherical Waves ◽  
Spatial Frequencies ◽  
Amplitude Spectra ◽  
Homogeneous Plane

The paper  considers  the  characteristics  determination  method  basing  on  amplifasometric  measurements  of  near  field  of the «antenna-radio-transparent radome» system with use of a spherical scanner. The method is based on determination of components of the amplitude spectra of homogeneous plane waves through the amplitudes of vector spherical waves of the tested antenna and the «antenna-radio-transparent radome» system. It is assumed that the radome has a regular surface shape and is a single-layer radome. The proposed method, in addition to determination of radiation characteristics, allows for the given antenna field polarization to determine the complex coefficient of passage thorough the radome as a function of spatial frequencies. It is also shown that it is possible to estimate the complex dielectric permittivity of a single-layer radome, both by calculating the components of uniform plane waves, and directly from the reduced field components on the outer surface of radome. Ways to study the radiophysical characteristics of theradom, are proposed.

Computational Technique for the Qualification of Focal Spot Size and Shape of Industrial Radioscopy Equipment Using Star Patterns

2020 ◽  
Vol 78 (4) ◽  
pp. 479-486
Author(s):  
Marcela Tatiana Fernandes Beserra ◽  
◽  
Ricardo Tadeu Lopes ◽  
Davi Ferreira de Oliveira ◽  
Claudio Carvalho Conti ◽  
...  
Keyword(s):  
Focal Spot ◽  
Spot Size ◽  
Computational Technique ◽  
Focal Spot Size ◽  
Size And Shape

One-dimensional numerical study of compressible flow ejector

AIAA Journal ◽  
2002 ◽  
Vol 40 ◽  
pp. 1469-1472
Author(s):  
S. Han ◽  
J. Peddieson
Keyword(s):  
Compressible Flow ◽  
Numerical Study ◽  
One Dimensional

Numerical study on near-field characteristics of landslide-generated impulse waves in channel reservoirs

2021 ◽  
Vol 595 ◽  
pp. 126012
Author(s):  
Xiaoliang Wang ◽  
Chuanqi Shi ◽  
Qingquan Liu ◽  
Yi An
Keyword(s):  
Numerical Study ◽  
Near Field ◽  
Impulse Waves
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