All-dielectric optical metasurfaces have recently attained much attention due to their ability to provide higher efficiencies than the more conventional plasmonic metasurfaces, and for their ability to readily work in both reflection and transmission. However, the functionality of traditional dielectric-based metasurfaces is fixed-by-design, i.e. the optical response is fixed by the size, arrangement and index of the nanoresonators. A far wider range of applications in many important technological/industrial fields, ranging from communications, to sensing, robotics, displays and much more, could be addressed if active/reconfigurable control were possible. One promising all-dielectric reconfigurable metasurface approach arises from the combination of high-index dielectric nanostructure arrays with chalcogenide phase-change materials (e.g. GeSbTe alloys). The latter can be electrically, optically or thermally switched between their crystalline and amorphous states, or to intermediate states between the two, with ultra-low energy consumption in a non-volatile manner and exhibit remarkably different optical properties between phases. It is therefore possible to achieve an all-dielectric reconfigurable metasurface by continuously tuning the phase states of the chalcogenide alloy. However, very few dielectric metasurface designs incorporating phase-change materials have been explored to date, and those that have been reported are switched through ex-situ means, while some form of in-situ switching is definitely required to meet real device applications.
To achieve this objective, we will (1) theoretically design and experimentally fabricate two reconfigurable all-dielectric phase-change metasurfaces whose in-situ switching is electrically realised by an integrated microheater and by a crossbar structure respectively, and (2) continuously tune the optical response of the designed metasurfaces for potential optical applications such as Lidar type beam steering).
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