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Hybrid Metalens for Miniaturised Ultraviolet Fluorescence Detection

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Author(s):
Li, Kezheng ; Martins, Augusto ; Bohora, Sanket ; Dhakal, Ashim ; Martins, Emiliano R. ; Krauss, Thomas F.
Total Authors: 6
Document type: Journal article
Source: ADVANCED OPTICAL MATERIALS; v. N/A, p. 7-pg., 2023-07-03.
Abstract

The advantages of metalenses to enable miniaturized systems have been well established, especially in the visible and infrared wavelength regimes. The ultraviolet (UV) presents a final frontier because feature size scales as the wavelength, so realizing a large size metalens with a high numerical aperture (NA) in the UV is a major challenge. Here, a single-layer, thin-film (450 nm) hybrid metalens with an NA of 0.9 and a diameter of 6.2 mm is presented. By combining a Fresnel lens and optimised binary gratings, the well-known shadowing effect of Fresnel lenses at high NA is avoided while being able to realize a large area lens. It is demonstrated that the combination of high NA and large area affords efficient detection of tryptophan-like fluorescence, which is a well-studied proxy for water contamination with faecal coliforms. The detection of tryptophan at levels better than 1 ppb, which corresponds to the low-risk category for drinking water according to the World Health Organization (WHO), is shown. It is also confirmed that the hybrid metalens fluorescence collection efficiency is 3.5 times higher than a high NA plano-convex lens used in state-of-the-art fluorometers, which demonstrates that the versatile metalens approach opens up new opportunities in the UV. (AU)

FAPESP's process: 20/00619-4 - Metasurfaces for imaging and sensing
Grantee:Emiliano Rezende Martins
Support Opportunities: Regular Research Grants
FAPESP's process: 21/06121-0 - Electromagnetic wave propagation through complex structures
Grantee:Ben-Hur Viana Borges
Support Opportunities: Regular Research Grants