MAKING BETTER USE OF LIGHT: ADDRESSING OPTICAL CHALLENGES WITH METASURFACES
thesisposted on 14.01.2021, 18:19 authored by Di WangDi Wang
The capability of light goes well beyond illumination, yet it is so underused in our lives because the control of light still largely relies on clumsy bulk lenses. Less than 10 years ago, a type of revolutionary devices made of nanometer scale optical elements – metasurfaces – was invented to control the light propagation and its energy dissipation with arbitrary degree of freedom, at unprecedentedly small volumes (although some would argue that the advent of metasurfaces came in the 1990s). Vast diversity of new discoveries has since been made possible, and many more existing applications have seen significant performance enhancement with the aid of metasurfaces.
In the scope of this work, I explore the use of a variety of metasurfaces to address several existing real-world challenges: sensing, optical heating, and data storage. Among these, three metasurfaces involve the world’s first two-dimensional material, graphene. I first investigate the graphene plasmonic resonator, which have been shown to be extremely sensitive single-molecule sensors. Graphene also has many intriguing properties in photodetection applications, such as lightweight, ultra-wide detection band, and ultrafast response speed. I have used two different metasurfaces to enhance the intrinsically low responsivity (sensitivity) of graphene photodetectors. Amidst the discussion of graphene photodetectors, I show the characterization result of plasmonic heating of metasurfaces, an essential process of the graphene photo-responsivity enhancement. Lastly, I present a multi-functional metasurface which can be used in optical steganography, encryption, and data storage. The proposed metasurface is compatible with large scale parallel readout, which outperforms current Blu-ray technology in both storage capacity and readout speed