Generation of Optical Needles Through Sliced-Pizza Scheme Metalens

The present paper introduces an innovative approach for creating an optical needle using a metasurface designed in a sliced pizza-shaped manner, where the focal length increases along the slice number. Specifically, we demonstrate that by using two opposing slices, the metasurface can focus light at a single point. To validate our proposed method, we propose a supporting phase equation and utilize it to simulate a metalens consisting of six slices. An optical needle of length \(21 \mu m(52 \lambda )\) and FWHM of \(1.1\mu m (7.8 \lambda )\) is simulated from a metalens of diameter \(10\mu m\) focusing at a length \(25\mu m\) from the first focusing slices of metalens, where \(\lambda\) is the wavelength of the light \((405 nm)\) . An additional length of \(8\mu m\) \((20 \lambda )\) was obtained, accounting for a greater depth of focus compared to a lens without slices.