The optical vortices structure controlling by changing the height of silicon ring gratings using high-performance computer systems

Abstract

Structured laser beams are currently being actively investigated in various fields of optics and photonics, in particular, in the field of metamaterials and metasurfaces. It is known to use metasurfaces to generate optical vortices in order to increase the throughput of optical communication systems. Also singular light beams have a special place in optics due to their use in a number of applications, including fiber optic information transmission, quantum informatics, wireless communication systems, and optical manipulation.
The diffraction of optical vortices of the first order on silicon subwavelength annular gratings of variable height study in this paper. The finite differences time domain (FDTD) method was used for numerical calculations (3D) of the propagation of laser radiation using a computing cluster with a capacity of 950 Gflops.
It is shown that varying the height of individual rings of subwavelength gratings significantly affects the diffraction pattern in the near zone. An analysis of the pattern of electric field intensity showed that by selecting the desired height of individual relief rings, it is possible to achieve a reduction in the size of the focal spot by more than 40% compared with a standard diffractive axicon. It should also be noted that in the case of a successive decrease in height from the edge of the element to the center, it is possible to form an extended region of reduced intensity on the optical axis with a higher intensity outside the optical axis (optical trap).

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Dmitry A. Savelyev
Samara National Research University; Image Processing Systems Institute оf RAS – Branch of the FSRC “Crystallography and Photonics” RAS
Russia

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