Electro-Optically Tunable Multifunctional Metasurfaces.

Shaping the flow of light at the nanoscale is a grand challenge for nanophotonics. It is now widely recognized that metasurfaces represent a chip-scale nanophotonics array technology capable of comprehensively controlling the wave front of light via appropriately configuring subwavelength antenna elements. Here, we demonstrate a reconfigurable metasurface that is multifunctional, i.e., notionally capable of providing diverse optical functions in the telecommunication wavelength regime, using a single compact, lightweight, electronically programmable array with no moving parts. By electro-optical control of the phase of light reflected from each identical element in a metasurface antenna array, we demonstrate a prototype programmable metasurface that is capable of both dynamic beam steering and reconfigurable light focusing. This powerful concept allows the programmer to create new functions, alter and improve existing functions, and toggle temporally between functions using a single device. Thus, reconfigurable multifunctional metasurfaces with arrays of tunable optical antennas can perform arbitrary optical functions by programmable array-level control of scattered light phase, amplitude, and polarization, similar to dynamic and programmable logic and memories in electronics.