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Sharp focus of a circularly polarized optical vortex at the output of a metalens illuminated by linearly polarized light

A.G. Nalimov1,2, V.V. Kotlyar1,2

1 IPSI RAS – Branch of the FSRC “Crystallography and Photonics” RAS, Molodogvardeyskaya 151, 443001, Samara, Russia,
2 Samara National Research University, Moskovskoye Shosse 34, 443086, Samara, Russia

 PDF, 1188 kB

DOI: 10.18287/2412-6179-2019-43-4-528-534

Pages: 528-534.

Full text of article: Russian language.

Abstract:
A three-level spiral metalens in an amorphous silicon film is designed. The metalens relief consists of two subwavelength gratings with a 220-nm period (for 633 nm wavelength) and depths of 90 and 170 nm. The metalens forms a left-hand circular polarized optical vortex with topological charge 2 when illuminated by a linearly polarized plane wave. The intensity distribution at a distance of 633 nm is in the form of a subwavelength circle, whereas the longitudinal projection of the Pointing vector has negative values on the optical axis, meaning that a backward energy flow occurs. Two subwavelength gratings with different depth act as quarter-wave plates, transforming linearly polarized light into circularly polarized light with a phase delay of (lambda)/2. This metalens combines functionalities of three optical elements: a quarter-wave plate, a spiral phase plate, and a high-NA diffraction metalens (NA close to unity).

Keywords:
optical vortex, polarization, quarter-wave plate, backward energy flow, metalens

Citation:
Nalimov AG , Kotlyar VV. Sharp focus of a circularly polarized optical vortex at the output of a metalens illuminated by linearly polarized light. Computer Optics 2019; 43(4): 528-534. DOI: 10.18287/2412-6179-2019-43-4-528-534.

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