Switchable Wavefront of Mid-Infrared Wave Using GeSbTe Metasurfaces

Abstract

Benefiting from the unprecedented superiority of phase change material on manipulating electromagnetic wave, germanium antimony telluride-based optical devices attract a lot of attention. Here, based on Pancharatnam-Berry phase, reflective metasurfaces are presented by using phase change material-germanium antimony telluride (Ge3Sb2Te6). They can manipulate reflection mode of terahertz wave and realize some functions. In order to verify this, three examples are numerically demonstrated, and they are gradient metasurface, vortex beam generator, and focusing lens. First of all, Ge3Sb2Te6 blocks are used to construct reflective wavefront of gradient metasurface, and then realize switching between anomalous reflection and mirror reflection. Secondly, vortex beam generators are designed with |l| = 1 and |l| = 2, and mode number of orbital angular momentum is reconstructed through the switching of Ge3Sb2Te6 between crystalline state and amorphous state. Finally, a reflective lens is presented, whose focus appears or disappears under different circular polarizations. By adjusting phase state of Ge3Sb2Te6, dynamic adjustment of focusing intensity is realized. Our design may have potential applications in the fields of terahertz switching and communication.

Keywords

• GeSbTe
• metasurface
• anomalous reflection
• orbital angular momentum
• Lens