Poynting vector and beam shape coefficients: on new families of symmetries (non-dark axisymmetric beams of the second kind and dark axisymmetric beams)

AbstractBoron Neutron Capture Therapy (BNCT) is facing a new era where different projects based on accelerators instead of reactors are under development. The new facilities can be placed at hospitals and will increase the number of clinical trials. The therapeutic effect of BNCT can be improved if a optimized epithermal neutron spectrum is obtained, for which the beam shape assembly is a key ingredient. In this paper we propose an optimal beam shaping assembly suited for an affordable low energy accelerator. The beam obtained with the device proposed accomplishes all the IAEA recommendations for proton energies between 2.0 and 2.1 MeV. In addition, there is an overall improvement of the figures of merit with respect to BNCT facilities and previous proposals of new accelerator-based facilities.

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Formation of Inverse Energy Flux in the Case of Diffraction of Linearly Polarized Radiation by Conventional and Generalized Spiral Phase Plates

Photonics ◽

10.3390/photonics8070283 ◽

2021 ◽

Vol 8 (7) ◽

pp. 283

Author(s):

Andrey Ustinov ◽

Svetlana Khonina ◽

Alexey Porfirev

Keyword(s):

Energy Flux ◽

Poynting Vector ◽

Numerical Study ◽

Longitudinal Component ◽

Light Fields ◽

Linearly Polarized ◽

Linearly Polarized Radiation ◽

Phase Plates ◽

Spiral Phase ◽

Polarized Radiation

Recently, there has been increased interest in the shaping of light fields with an inverse energy flux to guide optically trapped nano- and microparticles towards a radiation source. To generate inverse energy flux, non-uniformly polarized laser beams, especially higher-order cylindrical vector beams, are widely used. Here, we demonstrate the use of conventional and so-called generalized spiral phase plates for the formation of light fields with an inverse energy flux when they are illuminated with linearly polarized radiation. We present an analytical and numerical study of the longitudinal and transverse components of the Poynting vector. The conditions for maximizing the negative value of the real part of the longitudinal component of the Poynting vector are obtained.

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ORIENTATING MANIPULATION OF CYLINDRICAL PARTICLES WITH OPTICAL TWEEZERS

Journal of Nonlinear Optical Physics & Materials ◽

10.1142/s021886350800438x ◽

2008 ◽

Vol 17 (04) ◽

pp. 387-394 ◽

Cited By ~ 1

Author(s):

XIUDONG SUN ◽

XUECONG LI ◽

JIANLONG ZHANG

Keyword(s):

Escherichia Coli ◽

Carbon Nanotubes ◽

Laser Beam ◽

Optical Tweezers ◽

Optical Trap ◽

Polarization Direction ◽

Beam Shape ◽

E Coli ◽

Potential Applications ◽

Cylindrical Particles

Orientating manipulations of cylindrical particles were performed by optical tweezers. Vertical and horizontal manipulations of Escherichia coli (E. coli) were carried out by changing the trapping depth and the focused laser beam shape. It was found that carbon nanotubes bundles (CNTBs) could be rotated in the linear polarized optical trap until it orientated its long axis along the linear polarization direction of the laser beam. However, E.coli could not be orientated in this way. Corresponding mechanisms were discussed based on the anisomeric electric characters of CNTBs. These orientation technologies of cylindrical objects with optical trap have potential applications in assembling nano-electric devices.

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