This study presents a comprehensive investigation of a terahertz metasurface capable of simultaneous amplitude and phase modulation. We propose two distinct amplitude modulation approaches based on reflective metasurface at two different wavelengths: One employing Pancharatnam–Berry (PB) phase encoding for amplitude information, and the other utilizing dielectric layer structural modifications to modulate the reflection coefficient. The reflective PB mechanism demonstrates enhanced conversion efficiency when satisfying specific phase-matching conditions. Orbital angular momentum generation and focusing are demonstrated in a high-efficiency reflection configuration, and the designed vortex beam achieves well-defined quality and high purity. The dual-focus metasurface design validates the practicality of complex amplitude modulation strategies. Furthermore, rotational adjustment of the top layer and the dielectric layer thickness variation enable independent control of phase and amplitude, respectively. To verify its feasibility, three holographic imaging prototypes were designed using the Rayleigh–Sommerfeld algorithm, yielding experimental results closely aligned with theoretical predictions. This multifunctional metasurface provides a new idea for arbitrary control of electromagnetic manipulation and showcases promising potential for integrated photonic optics systems.
Cong et al. (Mon,) studied this question.