Fabry-Perot cavity-assisted metasurface for a low-crosstalk dual-narrowband encrypted display

Metasurfaces provide a powerful platform for high-resolution multichannel optical displays, and the conditional image reconstruction based on light wavelength and polarization further renders it highly promising for optical encryption. However, material dispersion causes these functionalities to persist at off-design wavelengths, leading to unintended image leakage or crosstalk. To address these issues, a metasurface-on-Fabry-Perot cavity (MoFP) platform is proposed and demonstrated. Unlike a standalone metasurface lacking pronounced resonant features, the MoFP enables spectrally filtered dual-narrowband transmission while simultaneously providing independent amplitude and polarization control at two bands centered at 800 and 1200 nm, respectively. A 3-bit intensity encoding is established and utilized to demonstrate a three-channel metasurface encrypted display. Simulation results show that a binary image is observed under circularly polarized illumination at 800 nm, while switching the wavelength to 1200 nm and placing an analyzer orientated at 0° and 45° gives rise to two different binary images. Most importantly, compared with a standalone metasurface, the MoFP can safely secure these images within a much narrower wavelength band with minimal crosstalk. We anticipate the proposed platform can give new insight to optical metasurface encryption.