Ultrathin double-focusing topological insulator lens

An ultrathin double-focusing lens, capable of simultaneously generating a plasmonic focus in the near-field region and a Fresnel-zone-plate based diffraction-limited focal spot in the far-field region, was designed using three-dimensional topological insulator (Sb2Te3). Our innovative double-focusing flat lens opens new opportunities for future compact devices with versatile functionalities, with potential applications ranging from optical imaging and information technology to biological sensing and medical diagnosis.