Hybrid Metalens for Miniaturised Ultraviolet Fluorescence Detection

Kezheng Li; Augusto Martins; Sanket Bohora; Ashim Dhakal; Emiliano Martins; Thomas Fraser Krauss

doi:10.1002/adom.202300852

Hybrid Metalens for Miniaturised Ultraviolet Fluorescence Detection

Kezheng Li^*, Augusto Martins, Sanket Bohora, Ashim Dhakal, Emiliano Martins, Thomas Fraser Krauss

^*Corresponding author for this work

Physics

Research output: Contribution to journal › Article › peer-review

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.

Original language	English
Article number	2300852
Number of pages	7
Journal	Advanced Optical Materials
Early online date	3 Jul 2023
DOIs	https://doi.org/10.1002/adom.202300852
Publication status	E-pub ahead of print - 3 Jul 2023

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Hybrid Metalens for Miniaturised Ultraviolet FluorescenceDetection
© 2023 The Authors.
Final published version, 1.61 MBLicence: CC BY

Cite this

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title = "Hybrid Metalens for Miniaturised Ultraviolet Fluorescence Detection",

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.",

author = "Kezheng Li and Augusto Martins and Sanket Bohora and Ashim Dhakal and Emiliano Martins and Krauss, {Thomas Fraser}",

note = "{\textcopyright} 2023 The Authors. ",

year = "2023",

month = jul,

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doi = "10.1002/adom.202300852",

language = "English",

journal = "Advanced Optical Materials",

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AU - Li, Kezheng

AU - Martins, Augusto

AU - Bohora, Sanket

AU - Dhakal, Ashim

AU - Martins, Emiliano

AU - Krauss, Thomas Fraser

PY - 2023/7/3

Y1 - 2023/7/3

N2 - 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.

AB - 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.

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