Frequency‐multiplexed pure‐phase microwave meta‐holograms using bi‐spectral 2‐bit coding metasurfaces
Shahid Iqbal, Hamid Rajabalipanah, Lei Zhang, Qiang Xiao, Ali Abdolali, Tie Jun Cui
Abstract
Abstract In this paper, a dual‐band reflective meta‐hologram is designed providing two distinct information channels whose field intensity distributions can be independently manipulated at the same time. The proposed pure‐phase meta‐hologram is composed of several frequency‐dispersive coding meta‐atoms possessing each of 2‐bit digital statuses of “00”, “01”, “10”, and “11” at either the lower (X‐band) or the higher (Ku‐band) frequency band. Relying on the weighted Gerchberg‐Saxton phase retrieval algorithm, different illustrative examples have been provided to theoretically inspect the dual‐band performance of our coding meta‐hologram. Numerical simulations validate the proposed frequency multiplexing meta‐holography with the ability to project two different high‐quality images with low cross‐talk on two X‐band and Ku‐band near‐field channels located at distinct pre‐determined distances from the metasurface plane. As proof of concept, two meta‐hologram samples are fabricated, and the experimental results corroborate well the numerical simulations and theoretical predictions. The designed meta‐hologram features all fascinating advantages of the coding metasurfaces while its performance overcomes that of previous studies due to providing two information channels rather than the conventional single‐channel holography. The frequency multiplexing acquired by the proposed bi‐spectral coding meta‐hologram may provide great opportunities in a variety of applications, such as data storage and information processing.