Sideband-free space–time-coding metasurface antennas

Applications such as microwave wireless communications, optical light fidelity, and light detection and ranging systems require advanced interfaces that can couple guided waves from in-plane sources into free space and manipulate the extracted free-space waves. Spatiotemporally modulated metasurfaces can control electromagnetic waves, but such systems are typically limited to free-space-only and waveguide-only platforms. Here we report a 1-bit space–time-coding metasurface antenna that can extract and mould guided waves into any desired free-space waves in both space and frequency domains. The waveguide-integrated metasurface antenna also provides a self-filtering phenomenon that overcomes the issue of sideband pollution found in traditional spatiotemporally modulated metasurfaces. To illustrate the capabilities of the approach, we use the metasurface antenna for high-efficiency frequency conversion, fundamental-frequency continuous beam scanning and independent control of multiple harmonics.