2017/05/31 by Ramon Paniagua-Dominguez, Ramón Paniagua‐Domínguez, Yefeng Yu +10 · 1 citation
Engineering · Materials Science · Physics and Astronomy · #Angular resolution (graph drawing) #Aperture (computer memory) #Diamond #Diffraction #Focal length #Focus (optics) #Lens (geology) #Materials science #Metamaterials and Metasurfaces Applications #Numerical aperture #Optics #Orbital Angular Momentum in Optics #Physics #Plasmonic and Surface Plasmon Research #Wavelength #physics.optics
paper · pdf · doi:10.1021/acs.nanolett.8b00368
12 pages, 5 figures
arxiv created 2018/01/10 · openalex publication_date 2018/02/27 · arxiv updated 2018/03/08 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The numerical aperture (NA) of a lens determines its ability to focus light and its resolving capability. Having a large NA is a very desirable quality for applications requiring small light-matter interaction volumes or large angular collections. Traditionally, a large NA lens based on light refraction requires precision bulk optics that ends up being expensive and is thus also a specialty item. In contrast, metasurfaces allow the lens designer to circumvent those issues producing high-NA lenses in an ultraflat fashion. However, so far, these have been limited to numerical apertures on the same order of magnitude as traditional optical components, with experimentally reported NA values of <0.9. Here we demonstrate, both numerically and experimentally, a new approach that results in a diffraction-limited flat lens with a near-unity numerical aperture (NA > 0.99) and subwavelength thickness (∼λ/3), operating with unpolarized light at 715 nm. To demonstrate its imaging capability, the designed lens is applied in a confocal configuration to map color centers in subdiffractive diamond nanocrystals. This work, based on diffractive elements that can efficiently bend light at angles as large as 82°, represents a step beyond traditional optical elements and existing flat optics, circumventing the efficiency drop associated with the standard, phase mapping approach.