An optically driven digital metasurface for programming electromagnetic functions

Metasurfaces are engineered surfaces that consist of subwavelength periodic elements and can be used to manipulate electromagnetic waves. Multifunctional or reconfigurable electromagnetic meta-devices based on a direct-current biasing system can be built using lumped electronic components. However, such meta-devices require bulky power supplies, field-programmable gate arrays, electrical wires and complex control circuits. Here, we report a digital metasurface platform that can be programmed optically to implement electromagnetic functions. Our digital platform has 6 × 6 subarrays, each of which contains 4 × 4 metasurface elements based on electronic varactors integrated with an optical interrogation network based on photodiodes. The interrogation network can convert visible light illumination patterns to voltages and applies bias to the metasurface elements, generating specific microwave reflection phase distributions. To illustrate the capabilities of our approach, we use the optically driven digital metasurface for external cloaking, illusion and dynamic vortex beam generation.