Large-angle deflection lens using supercell metasurfaces
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Nanotechnology (MPNAT), MSc
Publicerad
2024
Författare
Vahlin, Kerstin
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
A metasurface is an ultra-thin flat optical component, containing nanostructures
that scatter light. Due to the planar structure it can be monolithically integrated
with a vertical cavity surface-emitting laser (VCSEL), which removes alignment issues. With metasurfaces, full control of the wavefront is possible and hence a light
beam can be shaped in almost anyway. For instance focusing metalenses, lenses that
deflect light or vortex generators can be made. In many applications, for example
in bio-photonics, it is desirable to have a lens with high numerical aperture, which
entails deflection of light with large angels. The conventional way of designing a
metasurface is to use phase mapping, however that approach has a fundamental
limitation when it comes to creating steep angles. Therefor another type of metasurface based on diffracting elements have been implemented in this project. More
specifically, these metasurfaces are made in GaAs to enable integration with GaAs
VCSELs and the diffracting elements (supercells) are structured by nano-holes to
get the desired light shape and circumvent the issue of aspect ratio dependent etching (ARDE).
The metasurfaces were first simulated in COMSOL, then fabricated using electronbeam lithography and dry etching, and finally characterized. Metalenses utilizing
supercells that deflect light up to 85◦ have been achieved. The lenses deflect with
the desired angle and show a focusing effect. However the focus of the lenses is not
as tight as desired and calls for further investigation.
Beskrivning
Ämne/nyckelord
Metasurface, VCSEL, COMSOL Multiphysics