Samsung Advanced Institute of Technology

Spatial light modulators are essential optical elements in applications, such as digital holography, optical communications and biomedical imaging, which require the ability to regulate amplitude, phase and polarisation of light. With the push towards miniaturisation of optical components, static metasurfaces have been used as competent alternatives. These have evolved to active metasurfaces in which light wavefront manipulation can be done in a time-dependent fashion. The active metasurfaces reported so far, however, still show incomplete phase modulation (below 360°). Here we present an all-solid-state, electrically-tunable, reflective metasurface array that can generate a specific phase or a continuous sweep between 0 and 360° at an estimated rate of 5.4 MHz while independently adjusting the amplitude. The metasurface features 550 individually addressable nanoresonators in a 250×250 μm2 area with no micromechanical elements or liquid crystals. A key feature of our design is the presence of two independent control parameters (a top and bottom gate voltages) in each nanoresonator that are used to adjust the real and imaginary parts of the reflection coefficient independently. We demonstrate this array’s use in light detection and ranging (LiDAR) by performing a three dimensional depth scan of an emulated street scene consisting of a model car and a human figure up to a distance of 4.7 m.