Frequency-multiplexed pure-phase microwave meta-holograms using bi-spectral 2-bit coding metasurfaces

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.

Ultrathin dual-mode vortex beam generator based on anisotropic coding metasurface

“… Ref Frequency (GHz) Number layers Multiplexing style Thickness (mm) Meng et al 34 6.10 Single (with air gap) Dual-polarization 7.8 (0.26λ 0 at higher Freq.) Yu et al 38 5.8 Single (with air gap) Dual-band 6 (0.116λ 0 ) Iqbal et al 44 10.15 Bilayer Dual-band 2 (0.1λ 0 at higher Feq.) Xu et al 45 10.5 Bilayer Dual-polarization 5 (0.175λ 0 ) Our work 15 Single Dual-polarization 1.5 (0.075λ 0 ) …”

Metasurface Holography in the Microwave Regime

“…Another widely used multiplexing technique for microwave holography is frequencymultiplexing [114][115][116]. A multifunctional metasurface created by multiplexing the frequency and wavevector was proposed, as illustrated in Figure 6d.…”

Dual‐Polarized Tri‐Channel Encrypted Holography Based on Geometric Phase Metasurface

“…Moreover, the restricted dimensions of the 80 Â 80 unit cells metasurface also contributes to the limited quality of the hologram. [16,63,66] However, it should be noted that at higher frequencies with smaller of unit cells, more elements can be arranged on the metasurface to greatly improve the performance of the hologram.…”