Journal
APPLIED PHYSICS LETTERS
Volume 114, Issue 14, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.5092760
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Funding
- Russian Science Foundation [18-19-00595]
- Ministry of Science and Higher Education of Russian Federation [007-Uthorn/X3363/26]
- Russian Science Foundation [18-19-00595] Funding Source: Russian Science Foundation
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In this paper, we investigate a 16-sector spiral metalens fabricated on a thin film (130 nm) of amorphous silicon, consisting of a set of subwavelength binary diffractive gratings and with a numerical aperture that is close to unity. The metalens converts linearly polarized incident light into an azimuthally polarized optical vortex and focuses it at a distance approximately equal to the wavelength of the incident light, lambda = 633 nm. Using a scanning near-field optical microscope, it is shown experimentally that the metalens forms an elliptical focal spot with diameters smaller than the diffraction limit: FWHMx = 0.32 lambda (+/- 0.03 lambda) and FWHMy = 0.51 lambda (+/- 0.03 lambda). The experimental results are close to those of a numerical simulation using the FDTD method, with FWHMx = 0.37 lambda and FWHMy = 0.49 lambda. The technological errors due to manufacturing were taken into account in the simulation. This is the smallest focal spot yet obtained with a metalens. Published under license by AIP Publishing.
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