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Focusing of laser light by sectoral spiral metalens
Author(s): Sergey S. Stafeev; Victor V. Kotlyar; Anton G. Nalimov; Liam O'Faolain
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Paper Abstract

A large number of scientific papers are currently devoted to the investigation of metasurfaces, based on the subwavelength gratings. Such subwavelength gratings are anisotropic – TE- and TM-polarized waves propagated through them have a different phase. Based on this effect it is possible to create analogues of the classical half-wave plates, which rotate the direction of polarization. In this work we proposed a spiral metalens, which simultaneously converts linearly polarized light into an azimuthally polarized vortex beam and focuses it. This metalens is a combination of a spiral zone plate with a topological charge m = 1 (focal length f = 633 nm) and a sector subwavelength grating (period of 220 nm, relief depth of 120 nm, illumination wavelength of λ = 633 nm). The metalens was fabricated using electron beam lithography and ion etching in 130-nm thick amorphous silicon film. Using FDTD-method it was numerically shown that the metalens illuminated by a plane wave with linear polarization forms a circular focal spot with dimensions smaller than the scalar diffraction limit: FWHMx = 0.435λ and FWHMy = 0.457λ. The focusing by the fabricated metalens was investigated experimentally using scanning near-field optical microscope (Ntegra Spectra, NTMDT).

Paper Details

Date Published: 30 April 2019
PDF: 6 pages
Proc. SPIE 11025, Metamaterials XII, 110250Z (30 April 2019); doi: 10.1117/12.2520461
Show Author Affiliations
Sergey S. Stafeev, Image Processing Systems Institute (Russian Federation)
Samara National Research Univ. (Russian Federation)
Victor V. Kotlyar, Image Processing Systems Institute (Russian Federation)
Samara National Research Univ. (Russian Federation)
Anton G. Nalimov, Image Processing Systems Institute (Russian Federation)
Samara National Research Univ. (Russian Federation)
Liam O'Faolain, Cork Institute of Technology (Ireland)


Published in SPIE Proceedings Vol. 11025:
Metamaterials XII
Vladimír Kuzmiak; Peter Markos; Tomasz Szoplik, Editor(s)

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