Sharp Focusing of Light by Metasurface

We analyze the sharp focusing of an arbitrary optical vortex with the integer topological charge m and circular polarization in an aplanatic optical system. Explicit formulas to describe all projections of the electric and magnetic fields near the focal spot are derived. Expressions for the near-focus intensity (energy density) and energy flow (projections of the Pointing vector) are also derived. The expressions derived suggest that for a left-hand circularly polarized optical vortex with m > 2, the on-axis backward flow is equal to zero, growing in the absolute value as a power 2(m – 2) of the radial coordinate. These relations also show that upon the negative propagation, the energy flow rotates around the optical axis.

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Optical Vortices Sharp Focusing by Silicon Ring Gratings Using High-Performance Computer Systems

10.3233/faia210415 ◽

2021 ◽

Author(s):

Dmitry Savelyev

Keyword(s):

Time Domain ◽

Finite Difference Time Domain ◽

High Performance ◽

Light Propagation ◽

Longitudinal Component ◽

Laser Beams ◽

Minimum Size ◽

Sharp Focusing ◽

Direction Of Polarization ◽

Difference Time

The diffraction of vortex laser beams with circular polarization (with different direction of polarization rotation) by silicon ring gratings was investigated in this paper. The silicon diffractive axicons with different numerical apertures (NA) were considered as such ring gratings. The considered diffractive axicons are compared with single silicon circular protrusion (cylinder). The finite difference time domain method was used for Light propagation (3D) through the proposed silicon ring gratings and silicon cylinder. The possibility of subwavelength focusing by varying the height of the elements is demonstrated. In particular, it is numerically shown that a silicon cylinder forms a light spot with the minimum size (intensity) of the longitudinal component of the electric field FWHM is 0.32λ.

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Sharp focusing of beams with V-point polarization singularities

Computer Optics ◽

10.18287/2412-6179-co-884 ◽

2021 ◽

Vol 5 (45) ◽

pp. 643-653

Author(s):

V.V. Kotlyar ◽

A.G. Nalimov ◽

S.S. Stafeev ◽

A.A. Kovalev

Keyword(s):

Intensity Distribution ◽

Linear Polarization ◽

Light Field ◽

Focal Spot ◽

Polarization Direction ◽

Intensity Pattern ◽

Singularity Index ◽

Local Maxima ◽

Sharp Focus ◽

Sharp Focusing

It is theoretically and numerically shown that when tightly focusing an n-th order vector light field that has the central V-point (at which the linear polarization direction is undetermined), the polarization singularity index n, and a "flower"-shaped intensity pattern with 2(n-1) lobes it forms a transverse intensity distribution with 2(n-1) local maxima. At the same time, a vector light field with the polarization singularity index -n, which has the form of a "web" with 2(n+1) cells generates at the sharp focus a transverse intensity distribution with 2(n+1) local maxima. In the focal spot, either 2(n-1) or 2(n+1) V-point polarization singularities with alternating indices +1 or -1 are formed at the intensity zero.

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Mesoscale Acoustical Cylindrical Superlens

MATEC Web of Conferences ◽

10.1051/matecconf/201815501029 ◽

2018 ◽

Vol 155 ◽

pp. 01029 ◽

Cited By ~ 5

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.

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