A Global Phase-Modulation Mechanism for Flat-Lens Design

摘要

Flat lens also known as metasurface lens is drawing considerable attentionnowadays. Thus far, the metasurface lens has been achieved by engineeringlocal phase profile in deep subwavelength scale according to resonant ornon-resonant (or both) responses of nanoscatters to light. Such local phasemappings require precise control over each nanoscatter. In addition, thereis currently no metasurface lens that exhibits multiple functionalities. Here,a novel working mechanism, named as a global phase-modulation mechanism,for the flat-lens design is demonstrated. To illustrate this concept, abinary amplitude-only hologram is introduced, resulted from an interferencebetween an angular cosine wave and a spherical wave. The resultant flat lenscan be made extremely thin (60 nm) and is comprised of spatially shapedapertures. Such a technique allows to globally manipulate the diffractive wavevectors in the reciprocal space. Multiple focusing performances with a singleflat lens are demonstrated under different illumination beams including theplane-wave beam, vortex beam, and vector beam. In addition to imaging, theflat lens is able to Fourier transforming a complex self-accelerating Airy beam,which was not considered before. The presented global mechanism facilitatesnew capabilities and holds for multifunctional flat lens, with potential applicationsin areas such as imaging and optical information processing.