  Metasurfaces with unparalleled controllability of light have shown great
potential to revolutionize conventional optics. However, they mainly work with
free-space light input, which makes it difficult for full on-chip integration.
On the other hand, integrated photonics enables densely packed devices but has
limited free-space light controllability. Here, we show that judiciously
designed guided-wave-driven metasurfaces can mold guided waves into arbitrary
free-space modes to achieve complex free-space functions, such as beam steering
and focusing, with ultrasmall footprints and potentially no diffraction loss.
Based on the same concept together with broken inversion symmetry induced by
metasurfaces, we also realized direct orbital angular momentum (OAM) lasing
from a micro-ring resonator. Our study works towards complete control of light
across integrated photonics and free-space platforms, and paves new exciting
ways for creating multifunctional photonic integrated devices with agile access
to free space which could enable a plethora of applications in communications,
remote sensing, displays, and etc.
