The investigation of the features optical vortices focusing by ring gratings with the variable height using high-performance computer systems

Abstract The diffraction of vortex laser beams with circular polarization by ring gratings with the variable height was investigated in this paper. Modelling of near zone diffraction is numerically investigated by the finite difference time domain (FDTD) method. The changes in the length size of the light needle and focal spot size are shown depending on the type of the ring grating.

Download Full-text

The Investigation of the Effect of Changing the Height of Optical Elements on the Focal Spot Size Using High-Performance Computer Systems

Frontiers in Optics / Laser Science ◽

10.1364/fio.2020.jm6a.3 ◽

2020 ◽

Author(s):

Dmitry Savelyev

Keyword(s):

High Performance ◽

Focal Spot ◽

Computer Systems ◽

Spot Size ◽

Focal Spot Size ◽

Optical Elements ◽

High Performance Computer

Download Full-text

The sub-wavelength complex micro-axicons for focal spot size reducing using high-performance computer systems

Metamaterials XIII ◽

10.1117/12.2589220 ◽

2021 ◽

Author(s):

Dmitry A. Savelyev

Keyword(s):

High Performance ◽

Focal Spot ◽

Computer Systems ◽

Spot Size ◽

Focal Spot Size ◽

High Performance Computer ◽

Sub Wavelength

Download Full-text

Self-Focusing of Hermite-Cosh-Gaussian Laser Beams in Plasma under Density Transition

Advances in Optics ◽

10.1155/2014/942750 ◽

2014 ◽

Vol 2014 ◽

pp. 1-5 ◽

Cited By ~ 8

Author(s):

Manzoor Ahmad Wani ◽

Niti Kant

Keyword(s):

Laser Beam ◽

Plasma Density ◽

Focal Spot ◽

Beam Width ◽

Spot Size ◽

Laser Beams ◽

Equation Approach ◽

Focal Spot Size ◽

Self Focusing ◽

Small Spot

Self-focusing of Hermite-Cosh-Gaussian (HChG) laser beam in plasma under density transition has been discussed here. The field distribution in the medium is expressed in terms of beam-width parameters and decentered parameter. The differential equations for the beam-width parameters are established by a parabolic wave equation approach under paraxial approximation. To overcome the defocusing, localized upward plasma density ramp is considered, so that the laser beam is focused on a small spot size. Plasma density ramp plays an important role in reducing the defocusing effect and maintaining the focal spot size up to several Rayleigh lengths. To discuss the nature of self-focusing, the behaviour of beam-width parameters with dimensionless distance of propagation for various values of decentered parameters is examined by numerical estimates. The results are presented graphically and the effect of plasma density ramp and decentered parameter on self-focusing of the beams has been discussed.

Download Full-text

Minimal Focal Spot Size Measured Based on Intensity and Power Flow

Sensors ◽

10.3390/s21165505 ◽

2021 ◽

Vol 21 (16) ◽

pp. 5505

Author(s):

Victor V. Kotlyar ◽

Sergey S. Stafeev ◽

Vladislav D. Zaitsev

Keyword(s):

Linear Polarization ◽

Energy Flow ◽

Power Flow ◽

Focal Spot ◽

Spot Size ◽

Optical Vortices ◽

Focal Spot Size ◽

Minimum Diameter ◽

Circular Symmetry ◽

Energy Flows

It is shown, theoretically and numerically, that the distributions of the longitudinal energy flow for tightly focused light with circular and linear polarization are the same, and that the spot has circular symmetry. It is also shown that the longitudinal energy flows are equal for optical vortices with unit topological charge and with radial or azimuthal polarization. The focal spot has a minimum diameter (all other characteristics being equal), which is measured based on the intensity of an optical vortex with azimuthal polarization. The diameter of the focal spot calculated from the energy flow for light with circular or linear polarization is slightly larger (by a fraction of a percentage). The magnitude of the diameter based on the intensity plays a role in the interaction of light with matter, and the magnitude of the diameter based on the energy flux affects the resolution in optical microscopy which is crucial in sensorial applications.

Download Full-text

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

Computer Optics ◽

10.18287/2412-6179-co-862 ◽

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.

Download Full-text

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

Materials Evaluation ◽

10.32548/2020.me-04044 ◽

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

Download Full-text

Dependence of laser accelerated protons on laser energy following the interaction of defocused, intense laser pulses with ultra-thin targets

Laser and Particle Beams ◽

10.1017/s0263034611000395 ◽

2011 ◽

Vol 29 (3) ◽

pp. 345-351 ◽

Cited By ~ 22

Author(s):

C.M. Brenner ◽

J.S. Green ◽

A.P.L. Robinson ◽

D.C. Carroll ◽

B. Dromey ◽

...

Keyword(s):

Laser Pulse ◽

Focal Spot ◽

Laser Pulse Energy ◽

Laser Energy ◽

Spot Size ◽

Proton Flux ◽

Focal Spot Size ◽

Order Of Magnitude ◽

Laser Focal Spot ◽

Accelerated Protons

AbstractThe scaling of the flux and maximum energy of laser-driven sheath-accelerated protons has been investigated as a function of laser pulse energy in the range of 15–380 mJ at intensities of 1016–1018 W/cm2. The pulse duration and target thickness were fixed at 40 fs and 25 nm, respectively, while the laser focal spot size and drive energy were varied. Our results indicate that while the maximum proton energy is dependent on the laser energy and laser spot diameter, the proton flux is primarily related to the laser pulse energy under the conditions studied here. Our measurements show that increasing the laser energy by an order of magnitude results in a more than 500-fold increase in the observed proton flux. Whereas, an order of magnitude increase in the laser intensity generated by decreasing the laser focal spot size, at constant laser energy, gives rise to less than a tenfold increase in observed proton flux.

Download Full-text