All-Dielectric Metasurfaces for Sensing Applications

Prone, Giulia. All-Dielectric Metasurfaces for Sensing Applications. 2023, Doctoral Thesis, University of Basel, Faculty of Science.


Official URL: https://edoc.unibas.ch/93266/

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Dielectric metasurfaces are a family of flat-optical components that offer novel approaches to light manipulation, paving the way to exciting new applications. Regardless of the underlying operating theory, realizing such nanometer-sized devices calls for excellent fabrication accuracy, ideally on the sub-10 nm level, especially if resonance conditions need to be matched. Electron-beam lithography (EBL) is capable of achieving such feature sizes. Transparent substrates as used for optical transmission devices, however, present a big challenge as charge carriers accumulate in the substrate and cause long-range proximity effects. Furthermore, EBL's sequential exposure drastically limits the size of exposable areas, making it practically unaffordable for applications beyond research.
The aim of this thesis was to design and characterize structures engineered at the nano-scale, called metasurfaces, to implement compact optical elements and systems with capabilities beyond those of conventional refractive and diffractive optics.
The first chapter addresses the theoretical aspects of nanophotonics, metasurfaces, and sensing modalities.
The second chapter will include a brief overview of the metasurfaces concept, unit-cell design, and pattern choice. The design and simulation of tilted arrays of elliptical-shaped dielectric unit-cells will be presented.
In Chapter 3, the emphasis is on the metasurfaces manufacturing, beginning with the fabrication challenges that must be addressed to construct such a device, and a brief description of electron-beam lithography (EBL) and nanoimprint lithography (NIL). Following that, a three-layer transfer technique based on EBL and NIL is described. The results for master fabrication, substrate preparation, NIL patterning, pattern transfer, metrology, and overall fabrication will be discussed.
The fourth chapter will provide a customized microscopy setup for measuring the intensity variations of the created metasurfaces. First, a quick explanation of optical transmission spectroscopy and the overall signal processing method that will be used in the subsequent chapters will be provided. Following that, a brief overview of microfluidic devices with metasurfaces will be provided. The optical setup will then be presented, and system control will be demonstrated using commercially available software. Finally, the design and fabrication of a microfluidic chamber will be shown.
Chapter 5 will provide an overview of the various strategies for tuning dielectric metasurfaces, with a focus on the tunability provided by geometrical modifications and changes in the refractive index of the immediate environment.
In Chapter 6, a universal immobilization technique for structures exposing a sulfhydryl group (thiols) on silicon substrates will be shown, and contact-angle goniometric and XPS studies will be used to monitor surface changes. Following that, experimental streptavidin sensing will be demonstrated employing arrays of silicon nanoellipse resonators coated with biotin.
Finally, Chapters 7 and 8 will provide an overview of the preceding chapters' outcomes as well as an outlook on future applications.
Advisors:Mayor, Marcel and Calame, Michel and Galland, Christophe
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie > Molecular Devices and Materials (Mayor)
UniBasel Contributors:Mayor, Marcel and Calame, Michel
Item Type:Thesis
Thesis Subtype:Doctoral Thesis
Thesis no:14950
Thesis status:Complete
Number of Pages:xii, 114, xliii-xxxix
Identification Number:
  • urn: urn:nbn:ch:bel-bau-diss149500
edoc DOI:
Last Modified:14 Mar 2023 05:30
Deposited On:13 Mar 2023 12:54

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