A Metalens with Near-Unity Numerical Aperture
| Autor: | Paniagua-Dominguez, Ramon, Yu, Ye Feng, Khaidarov, Egor, Choi, Sumin, Leong, Victor, Bakker, Reuben M., Liang, Xinan, Fu, Yuan Hsing, Valuckas, Vytautas, Krivitsky, Leonid A., Kuznetsov, Arseniy I. |
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| Rok vydání: | 2017 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1021/acs.nanolett.8b00368 |
| Popis: | 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 <0.9. 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 sub-wavelength thickness (~{\lambda}/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{\deg}, represents a step beyond traditional optical elements and existing flat optics, circumventing the efficiency drop associated to the standard, phase mapping approach. Comment: 12 pages, 5 figures |
| Databáze: | arXiv |
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