Focusing of laser light by sectoral spiral metalens

Sergey S. Stafeev; Victor V. Kotlyar; Anton G. Nalimov; Liam O'Faolain

doi:10.1117/12.2520461

30 April 2019 Focusing of laser light by sectoral spiral metalens

Sergey S. Stafeev, Victor V. Kotlyar, Anton G. Nalimov, Liam O'Faolain

Proceedings Volume 11025, Metamaterials XII; 110250Z (2019) https://doi.org/10.1117/12.2520461
Event: SPIE Optics + Optoelectronics, 2019, Prague, Czech Republic

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).

Citation Download Citation

Sergey S. Stafeev, Victor V. Kotlyar, Anton G. Nalimov, and Liam O'Faolain "Focusing of laser light by sectoral spiral metalens", Proc. SPIE 11025, Metamaterials XII, 110250Z (30 April 2019); https://doi.org/10.1117/12.2520461

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