Physics Commons^™

Subwavelength Grating-Based Spiral Metalens For Tight Focusing Of Laser Light, Victor V. Kotlyar, Sergey S. Stafeev, Anton G. Nalimov, Liam O'Faolain

Cappa Publications

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, k ¼ 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 ¼ 0.32k (60.03k) and …