Open AccessFlat optics in high numerical aperture broadband imaging systems
Author(s) -
Daniel Werdehausen,
Sven Burger,
Isabelle Staude,
Thomas Pertsch,
Manuel Decker
Publication year - 2020
Publication title -
journal of optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 95
eISSN - 2040-8986
pISSN - 2040-8978
DOI - 10.1088/2040-8986/ab8ea2
Subject(s) - broadband , numerical aperture , scroll , optics , computer science , diffraction , algorithm , materials science , physics , mechanical engineering , wavelength , engineering
Diffractive optical elements (DOEs) remain highly underutilized in broadband optical systems even though different technologies for DOEs including échelette-type gratings (EGs), multilevel DOEs, and metagratings have been introduced. Specifically, nanocomposite-enabled EGs can achieve efficiencies of close to 100 % throughout the visible spectrum, but only for relatively small diffraction angles. Therefore, the question remains if they are suitable for high-numerical-aperture (NA) systems. Here we show that this is indeed the case. To this end, we first demonstrate that macroscopic nanocomposite-enabled diffractive lenses (DLs) can achieve perfect broadband focusing up to a NA of 0.03. We then derive analytic relationships and investigate prototypical optical designs to show that this threshold fully covers the requirements of high-end imaging systems with NA ⩾ 1. This holistic all-system analysis demonstrates that the individual NA of a DL in a broadband imaging system is one to two orders of magnitude lower than the overall system’s NA. This shows that high-NA flat optical elements are not required for high-NA broadband systems. Therefore, nanocomposite-enabled EGs can unlock the full potential of DOEs for broadband optical systems, whereas other technologies cannot fulfill their high efficiency requirements.