Abstract
Metasurfaces have recently gained increasing attention and shown great potential in replacing bulk optics with ultracompact flat metadevices, owing to their unprecedented capabilities of molding optical fields with surface‐confined configurations and exceedingly low losses. However, most existing metasurfaces are typically passive and feature well‐defined responses determined by material compositions and configurations, which severely limit the functionalities in intelligent and adaptive nanophotonics. Therefore, it is highly desired to realize active metasurfaces with dynamic modulation postfabrication. Herein, a highly efficient tunable metawaveplate at the telecom wavelength of 1.55 μm by structuring the phase‐change alloy Sb2Se3 is designed, which can switch from a half‐waveplate to a quarter‐waveplate once Sb2Se3 transits from the amorphous to the crystalline state. Capitalizing on the designed Sb2Se3 meta‐atom and the Pancharatnam–Berry phase, two switchable meta‐devices capable of actively shaping the wavefronts of the transmitted waves are proposed, including tunable beam steering and metalens with tailored focal intensity. The presented tunable metasurfaces can open new avenues for adaptive photonics with advanced functionalities.
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