High-Resolution OAM-Multiplexed Holography Based on Cascaded Metasurfaces

Orbital angular momentum (OAM) is an ideal wavefront multiplexing variable for metasurface holography. OAM can offer an unbounded discrete basis to construct an arbitrarily large Hilbert space, which leads to a theoretically infinite channel capacity in quantum information protocols [1]. Recently, a series of OAM-selective metasurface holography methods have been proposed with a camera-based spatial filter to remove crosstalk from other OAM channels. However, this approach wastes most of the camera's sensing area, limiting spatial resolution. The ratio of the largest OAM mode diameter to the sampling interval <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\gamma$</tex> must remain below 1 [2]. To address this, we propose a high-resolution OAM-multiplexing strategy using cascaded metasurfaces. As shown in Fig. 1a, the first metasurface acts as a classic OAM-selective filter, while the second functions as a beam redirector, shaping beams to arbitrary sampling intervals.