On-Chip Wavefront Shaping with Rewritable Phase-Change Metasurfaces

Photonic integrated circuits (PICs) with rapid programming capability are highly desirable to realize flexible photonic networks. Phase change technology offers nonvolatile programmability in PICs. Here, an alternate way of controlling the light flow to interferometers, directional couplers, and phase shifters in the photonic integrated circuits, that is on-chip programmable metasurfaces is reported. Compact and low-loss on-chip metasurfaces can be demonstrated on a Sb<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Se<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> thin film using direct laser writing. On-chip focusing and splitting are realized with a single layer of the on-chip metasurface. Also, a more complex machine learning task of pattern recognition is accomplished by a metasystem composed of multiple cascaded on-chip metasurfaces.