Resonant tunneling diode integrated with an extremely short focal length polarization-independent collimating metalens

Abstract Terahertz continuous-wave sources have been rapidly developed to cover the terahertz gap. However, integrating metasurface-based optical elements with sources remains limited due to the challenges of simultaneously designing multiple optical properties. Here, we demonstrate a 1.0-mm extremely short focal length collimating metalens employing a polarization-independent metasurface with a high refractive index, low reflectance, and high transmittance. The fabricated collimating metalens enhances the directivity of a resonant tunneling diode and narrows the beam at 0.312 THz. Terahertz flat optics based on our original metasurface can provide an attractive platform of optical elements for emerging industrial applications, including 6G wireless communications.