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

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.

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

Journal of Physics Conference Series ◽

10.1088/1742-6596/2086/1/012166 ◽

2021 ◽

Vol 2086 (1) ◽

pp. 012166

Author(s):

D A Savelyev

Keyword(s):

High Performance ◽

Focal Spot ◽

Fdtd Method ◽

Spot Size ◽

Laser Beams ◽

Optical Vortices ◽

Focal Spot Size ◽

Near Zone ◽

High Performance Computer ◽

Difference Time

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.

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Minimizing the Bright/Shadow Focal Spot Size with Controlled Side-Lobe Increase in High-Numerical-Aperture Focusing Systems

Advances in Optical Technologies ◽

10.1155/2013/267684 ◽

2013 ◽

Vol 2013 ◽

pp. 1-13 ◽

Cited By ~ 1

Author(s):

S. N. Khonina ◽

S. G. Volotovskiy

Keyword(s):

Focal Spot ◽

Numerical Aperture ◽

Optical Element ◽

Spot Size ◽

Side Lobe ◽

Amplitude Dependence ◽

Focal Spot Size ◽

Phase Dependence ◽

System Output ◽

Incident Waves

Minimizing the bright/shadow focal spot size for differently polarized incident waves through the additional apodization of the focusing system output pupil by use of an optical element with the vortex phase dependence on angle and the polynomial amplitude dependence on radius is studied. The coefficients of the radial polynomial were optimized with the aim of fulfilling certain conditions such as the energy efficiency preservation and keeping the side lobes under control. The coefficients were chosen so as to minimize the functional using Brent’s method.

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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

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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.

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Trapping of Nano-Particles Using a Near-Field Optical Fiber Probe

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.516.90 ◽

2012 ◽

Vol 516 ◽

pp. 90-95

Author(s):

Bing Hui Liu ◽

Li Jun Yang ◽

Yang Wang

Keyword(s):

Near Field ◽

Fdtd Method ◽

Laser Wavelength ◽

Nano Particles ◽

Minimum Size ◽

Fiber Probe ◽

Circular Shape ◽

Optical Fiber Probe ◽

Fibre Probe ◽

Difference Time

By employing a generalization of the conservation law for momentum using the finite difference time domain (FDTD) method, the feasibility of using a near-field optical fibre probe to create near-field optical trapping is investigated. Numerical results indicate that the scheme is able to trap nanoparticles with diameters of tens of nanometres in a circular shape with lower laser intensity. Using the built system with a tapered metal-coated fibre probe, 120 nm polystyrene particles are trapped in a multi-circular shape with a minimum size of 400 nm. They are at a resolution of λ/7 (λ: laser wavelength) and d (d: tip diameter of fiber probe), respectively.

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The determination of the focal spot size of an X-ray tube from the radiation beam profile

Radiation Measurements ◽

10.1016/j.radmeas.2015.09.010 ◽

2015 ◽

Vol 82 ◽

pp. 138-145 ◽

Cited By ~ 3

Author(s):

A.D. Oliveira ◽

M.J. Fartaria ◽

J. Cardoso ◽

L.M. Santos ◽

C. Oliveira ◽

...

Keyword(s):

Focal Spot ◽

Spot Size ◽

Beam Profile ◽

Focal Spot Size ◽

Radiation Beam ◽

X Ray

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Bremsstrahlung emission profile from intense laser-solid interactions as a function of laser focal spot size

Plasma Physics and Controlled Fusion ◽

10.1088/1361-6587/aaf596 ◽

2019 ◽

Vol 61 (3) ◽

pp. 034001 ◽

Cited By ~ 4

Author(s):

C D Armstrong ◽

C M Brenner ◽

E Zemaityte ◽

G G Scott ◽

D R Rusby ◽

...

Keyword(s):

Focal Spot ◽

Spot Size ◽

Intense Laser ◽

Focal Spot Size ◽

Emission Profile ◽

Bremsstrahlung Emission ◽

Laser Focal Spot ◽

Laser Solid Interactions

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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.

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