Dynamic Phase‐Change Metawaveplates for Advanced Wavefront Shaping

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 surface‐confined configurations exceedingly low losses. However, most existing metasurfaces are typically passive feature well‐defined responses determined by material compositions configurations, which severely limit the functionalities intelligent adaptive nanophotonics. Therefore, it is highly desired realize active dynamic modulation postfabrication. Herein, a efficient tunable metawaveplate at telecom wavelength 1.55 μm structuring phase‐change alloy Sb 2 Se 3 designed, can switch from half‐waveplate quarter‐waveplate once transits amorphous crystalline state. Capitalizing on designed meta‐atom Pancharatnam–Berry phase, two switchable meta‐devices capable actively shaping wavefronts transmitted waves proposed, including beam steering metalens tailored focal intensity. The presented open new avenues for photonics advanced functionalities.