Design of a terahertz encoding metalens with adjustable focusing intensity

This paper presents a terahertz coded metalens with adjustable focusing efficiency. By integrating the phase change material GST-225 with the plasma metasurface and employing the transmission phase principle for phase modulation, flexible control of the single-focus focusing efficiency is achieved. Additionally, a dual-focus focusing metalens is devised. Leveraging the far-field scattering principle of the coded metasurface, the focal angle of the metalens can be adjusted, and it can be expanded to a dual-focus system through complex coding addition. In this system, by adjusting the crystallinity corresponding to different codes, the system can show different focusing efficiencies at each focus. The proposed dual-focus in this paper enables separate adjustment of focusing efficiency, offering a promising solution for on-chip and tunable devices in terahertz imaging and communication systems.