A Metalens with a Near-Unity Numerical Aperture
Top Cited Papers
- 27 February 2018
- journal article
- research article
- Published by American Chemical Society (ACS) in Nano Letters
- Vol. 18 (3), 2124-2132
- https://doi.org/10.1021/acs.nanolett.8b00368
Abstract
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 ultra-flat fashion. However, so far, these have been limited to numerical apertures on the same order of traditional optical components, with experimentally reported values of NA 0.99) and sub-wavelength 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 sub-diffractive diamond nanocrystals. This work, based on diffractive elements able to 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 to the standard, phase mapping approach.Keywords
Funding Information
- National Research Foundation Singapore (NRF-CRP14-2014-04)
- Data Storage Institute
- Science and Engineering Research Council (152 73 00025)
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