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Metasurfaces are the future of ultrathin optics and can be engineered to generate any desired optical
output by varying the material and geometry of its constituents called “meta-atoms”. In this talk, I
would briefly discuss the basic working principles of metasurface and how their subwavelength
nature provides them with unique properties. I will then continue by showing some state-of-the-art
applications by manipulating the meta-atoms by several unconventional means i.e. by using alloys
or hybrid metal-dielectric as materials or random stealthy hyperuniform pattern as geometry. I will
discuss the novel fabrication method of plasmonic metalenses and holograms of any composition of
the AuAg alloys, only by heating nanostructures with a bilayer of Au and Ag of varying thickness at
a very low temperature of 300°C that retains the shape perfectly thus precluding the need for alloy
targets. In the next section, I would show how the addition of dielectric with metal metamorphosises
the spectrum, the low loss from the dielectric gives rise to multiple multipoles while the metal
enhances the electric field, the interaction of which either gives rise to sharper resonances or pure
magnetic modes that are unavailable with pure metal or dielectric. Following this, Si nanopillars
with stealthy hyperuniform pattern are fabricated to be used as a PDMS mould which are integrated
with solar cells to enhance the absorption and efficiency of the photocurrent generation. Following
this I will discuss how in practice dielectric metasurfaces can be designed to mimic the
functionalities of traditional optical components like beam splitter, polarizer etc. and can thus be
potential ultrathin alternatives to bulky optical components. Moreover, metasurfaces based on spin-
orbit interaction can be used to generate vortex beams with multiple orthogonal directions that are
applied in optical trapping and quantum communication. These metasurfaces can be further
assembled to make novel “meta-devices” that are lab-on-a-chip optical setups and are the future of
ultrathin optics. |