Design of a broadband achromatic dielectric metalens for linear polarization in the near-infrared spectrum

Abstract

The elimination of broadband chromatic aberrations is a crucial factor for focusing lenses. Conventional refractive glass lenses are bulky, unwieldy, and eradicating their chromatic dispersion is complicated. Dielectric metalenses represent a promising alternative due to their ultra-thin, ultra-compact, single-layer, and planar profile on the order of the wavelength or below. Here, we design an achromatic dielectric metalens for linear polarization that achieves continuous focusing performance over an ultra-broad band from 1.31μm to 1.55μm. The metalens consists of a single layer of elliptic Si nanocylinders with different radii meticulously designed for an accurate manipulation of the phase profile. The focal length remains constant with a less than 1.6% alternation over the entire operation bandwidth (compared with 9.4% alternation of a chromatic metalens). The high NA (0.36), high focal efficiency (average over 50%), and small FWHM all corroborate the excellent focusing performance of our metalens. Furthermore, the continuous broadband focusing performance is preserved under oblique incidence (10° angle) with a stable focal length. The designed metalens offers important opportunities for applications in linear polarized optics, fiber sensors, laser scanning fluorescence microscopy, optical signal transmission, and integrated on-chip devices in the forthcoming future.