Radiation torque on solid spheres and drops centered on an acoustic helicoidal Bessel beam.

Transformation of a Bessel beam by a lens results in the formation of a “perfect” vortex beam (PVB) in the focal plane of the lens. The PVB has a single-ring cross-section and carries an orbital angular momentum (OAM) equal to the OAM of the “parent” beam. PVBs have numerous applications based on the assumption of their ideal ring-type structure. For instance, we proposed using terahertz PVBs to excite vortex surface plasmon polaritons propagating along cylindrical conductors and the creation of plasmon multiplex communication lines in the future (Comput. Opt. 2019, 43, 992). Recently, we demonstrated the formation of PVBs in the terahertz range using a Bessel beam produced using a spiral binary silicon axicon (Phys. Rev. A 2017, 96, 023846). It was shown that, in that case, the PVB was not annular, but was split into nested spiral segments, which was obviously a consequence of the method of Bessel beam generation. The search for methods of producing perfect beams with characteristics approaching theoretically possible ones is a topical task. Since for the terahertz range, there are no devices like spatial modulators of light in the visible range, the main method for controlling the mode composition of beams is the use of diffractive optical elements. In this work, we investigated the characteristics of perfect beams, the parent beams being quasi-Bessel beams created by three types of diffractive phase axicons made of high-resistivity silicon: binary, kinoform, and “holographic”. The amplitude-phase distributions of the field in real perfect beams were calculated numerically in the approximation of the scalar diffraction theory. An analytical expression was obtained for the case of the binary axicon. It was shown that a distribution closest to an ideal vortex was obtained using a holographic axicon. The resulting distributions were compared with experimental and theoretical distributions of the evanescent field of a plasmon near the gold–zinc sulfide–air surface at different thicknesses of the dielectric layer, and recommendations for experiments were given.

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A novel model for the interpretation of small-angle scattering experiments of self-affine structures

Journal of Applied Crystallography ◽

10.1107/s0021889809048791 ◽

2009 ◽

Vol 43 (1) ◽

pp. 12-16 ◽

Cited By ~ 6

Author(s):

Gerald J. Schneider ◽

D. Göritz

Keyword(s):

Small Angle ◽

Analytical Description ◽

Small Angle Scattering ◽

Filled Rubber ◽

Angle Scattering ◽

Affine Structures ◽

Novel Theory ◽

First Time ◽

Novel Model ◽

Solid Spheres

A novel theory is presented which allows, for the first time, the analytical description of small-angle scattering experiments on anisotropic shaped clusters of nanoparticles. Experimentally, silica-filled rubber which is deformed is used as an example. The silica can be modelled by solid spheres which form clusters. The experiments demonstrate that the clusters become anisotropic as a result of the deformation whereas the spheres are not affected. A comparison of the newly derived model function and the experiments provides, for the first time, microscopic evidence of the inhomogeneous deformation of clusters in the rubbery matrix.

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Phase Profile in Superposition of Bessel Beam Modulates Local Axial Optical Force on Rayleigh and Mie Dielectric Spheres

Optik ◽

10.1016/j.ijleo.2021.167032 ◽

2021 ◽

pp. 167032

Author(s):

Eungkyu Lee ◽

Seunghyun Moon ◽

Tengfei Luo

Keyword(s):

Bessel Beam ◽

Optical Force ◽

Phase Profile ◽

Dielectric Spheres

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Non-diffraction-length Bessel-beam femtosecond laser drilling of high-aspect-ratio microholes in PMMA

Optik ◽

10.1016/j.ijleo.2021.166295 ◽

2021 ◽

Vol 229 ◽

pp. 166295

Author(s):

Haoran Wang ◽

Fan Zhang ◽

Kaiwen Ding ◽

Ji'an Duan

Keyword(s):

Aspect Ratio ◽

Femtosecond Laser ◽

High Aspect Ratio ◽

Bessel Beam ◽

Laser Drilling

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A mesoscopic model for compression of granular materials

EPJ Web of Conferences ◽

10.1051/epjconf/201818301054 ◽

2018 ◽

Vol 183 ◽

pp. 01054

Author(s):

Elisha Rejovitzky

Keyword(s):

Experimental Data ◽

Wave Propagation ◽

Granular Materials ◽

Mechanical Model ◽

Sound Speed ◽

Bulk Material ◽

High Sensitivity ◽

Water Fraction ◽

Protective Structures ◽

Solid Spheres

The design of protective structures often requires numerical modeling of shock-wave propagation in the surrounding soils. Properties of the soil such as grain-grading and water-fraction may vary spatially around a structure and among different sites. To better understand how these properties affect wave propagation we study how the meso-structure of soils affects their equation of state (EOS). In this work we present a meso-mechanical model for granular materials based on a simple representation of the grains as solid spheres. Grain-grading is prescribed, and a packing algorithm is used to obtain periodic grain morphologies of tightly packed randomly distributed spheres. The model is calibrated by using experimental data of sand compaction and sound-speed measurements from the literature. We study the effects of graingrading and show that the pressures at low strains exhibit high sensitivity to the level of connectivity between grains. At high strains, the EOS of the bulk material of the grains dominates the behavior of the EOS of the granular material.

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