Optical Vortices Sharp Focusing by Silicon Ring Gratings Using High-Performance Computer Systems

Abstract

The diffraction of vortex laser beams with circular polarization (with different direction of polarization rotation) by silicon ring gratings was investigated in this paper. The silicon diffractive axicons with different numerical apertures (NA) were considered as such ring gratings. The considered diffractive axicons are compared with single silicon circular protrusion (cylinder). The finite difference time domain method was used for Light propagation (3D) through the proposed silicon ring gratings and silicon cylinder. The possibility of subwavelength focusing by varying the height of the elements is demonstrated. In particular, it is numerically shown that a silicon cylinder forms a light spot with the minimum size (intensity) of the longitudinal component of the electric field FWHM is 0.32λ.

The comparison of the optical vortices focusing by silicon diffraction axicons and ring gratings with variable relief heights using high-performance computer systems

“…Previous studies have shown that under certain conditions, a conventional round protrusion can be used to recognize polarization and focusing, and the focusing will be better than for a diffractive axicon with a similar grating size 32,43 . But the relief height also plays a key role 44,45 .…”

The optical vortices focusing by subwavelength microelements with variable relief height using high-performance computer systems

“…The numerical calculations (3D) of the laser radiation propagation were performed using the finite difference time domain method (FDTD) using high-performance computer systems in the Meep software package [69][70][71][72] . The calculations were carried out on a computing cluster with a capacity of 850 Gflop.…”

The Features of the Optical Traps Formation Using Silicon Ring Gratings with Variable Height

“…Diffraction optics are often used to form vortex beams [62][63][64][65][66][67][68][69][70][71][72][73][74][75][76], including multi-order diffractive optical elements [65][66][67], spiral phase plates [68][69][70], spiral and twisted axicons [71][72][73], and elements with a complex surface shape [73,74]. It is known that one can use spiral phase microplates manufactured at the end of a waveguide to form vortex beams in optical connector systems in data centers [76].…”