Reflective moiré metasurface: Challenges and opportunities

Dynamic beamforming is a critical technique in applications like radar detection, holographic imaging, and reconfigurable intelligent surfaces (RIS). Current approaches to dynamic beamforming rely heavily on active components (e.g., PIN diodes, varactor diodes), leading to substantial cost challenges in large-scale deployments, particularly at millimeter-wave and subterahertz frequencies, where these components are prohibitively expensive or unavailable. In 2022, we proposed a mechanism to achieve dynamic beamforming based on two closely stacked reflective moiré metasurfaces. By making mutual in-plane rotation of the two metasurfaces, we can continuously direct the beam in reflective space and achieve almost any beam shape and trajectory with judicious pattern selection. Our design offers a cost-effective solution for dynamic beamforming in RIS applications and unveils an alternative approach to explore the physics of programmable metasurfaces. Here, we provide an overview of the reflective moiré metasurface, explaining its principles and design, addressing current challenges with potential solutions, and envisioning its applications and future directions.