Bilayer Metasurfaces for Angular Control of Light

ABSTRACT Compound meta‐optics – devices made of multiple stacked metasurfaces – allow overcoming many of the limitations of single‐layer meta‐optics. However, designing multi‐layer devices to obtain desired and complex functionalities is often challenging, due to the inter‐layer coupling and the large number of degrees of freedom. Here, we explore a general approach to use compound meta‐optics to obtain nontrivial angular‐dependent transmission profiles. Our approach relies on distributing different sub‐parts of the desired angular response across the different layers of a multi‐layer device, while simultaneously minimizing inter‐layer reflections. We demonstrate the feasibility of this approach by designing and numerically testing a bilayer metasurface that implements an angular bandpass filter with strongly asymmetric edges — a sharp rising edge close to normal incidence and a much smoother falling edge at much larger angles. This behavior is obtained by combining, within the same bilayer device, the sharp and smooth responses of nonlocal and local metasurfaces. Full‐wave simulations confirm the feasibility of this strategy for both 1D and 2D devices, yielding designs with high efficiency, excellent isotropy, and very large tolerance to fabrication misalignments. Importantly, we show that our approach allows individual control over different portions of the angular response. Finally, we discuss possible uses of the optimized angular bandpass filter in applications such as noise filtering in holographic displays and noise‐resilient analog image processing. Our work opens up opportunities for the rational design of multi‐layer meta‐optics with tailored angle‐dependent scattering.