  Designing reconfigurable metasurfaces that can dynamically control scattered
electromagnetic waves and work in the near-infrared (NIR) and optical regimes
remains a challenging task, which is hindered by the static material property
and fixed structures. Phase change materials (PCMs) can provide high contrast
optical refractive indexes at high frequencies between amorphous and crystal
states, therefore are promising as feasible materials for reconfigurable
metasurfaces. Here, we propose a hybrid metasurface that can arbitrarily
modulate the complex amplitude of incident light with uniform amplitude and
full $2\pi$ phase coverage by utilizing composite concentric rings (CCRs) with
different ratios of gold and PCMs. Our designed metasurface possesses a
bi-functionality that is capable of splitting beams or generating vortex beams
by thermal switching between metal and semiconductor states of vanadium oxide
(VO2), respectively. It can be easily integrated into low loss photonic
circuits with an ultra-small footprint. Our metadevice serves as a novel
paradigm for active control of beams, which may open new opportunities for
signal processing, memory storage, holography, and anti-counterfeiting.
