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Yifei Wang1 Patrick Landreman1 Kye Okabe1 Umberto Celano1 2 H.S. Philip Wong1 Mark Brongersma1

1, Stanford University, Stanford, California, United States
2, imec, Leuven, , Belgium

Active tuning of nanophotonic devices has many potential applications. Such tuning can be achieved by changing either the shape or material properties of a structure. Phase-change materials, such as Germanium Antimony Tellurium (GST), are of particular interest as they can exhibit large and non-volatile changes in their refractive index. Pulsed laser illumination has effectively been used to induce phase transitions in GST-based optical devices. Such changes can cause large changes in the optical scattering properties in the near-infrared. However, electrical tuning of GST-based photonic antennas and metamaterials has remained elusive.
Here we present optical antennas and metasurfaces combining phase-change material and plasmonic structures. By inducing phase-changes electrically in optical antennas, we achieve reversible multi-level tuning of scattered light intensity by more than 30%. Metasurfaces, designed as a perfect absorber, show over a 3-fold enhancement of reflection in the visible wavelength range between phases. This work demonstrates a first GST-based active metasurfaces working in the visible wavelengths, showing the potential to develop randomly-accessible metamaterial platforms in which metamolecules can be individually controlled.

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