Double-sided printed terahertz collimating metalens mounted on a resonant tunneling diode

Integrating optically thin metasurfaces with continuous-wave (CW) terahertz sources offers an alternative to conventional bulky optical elements for manipulating terahertz waves. However, planar optical elements composed of metasurfaces have yet to be actively adopted in CW terahertz sources due to limited fabrication methods suitable for micrometer-scale meta-atoms. Here, we fabricate two types of printed terahertz collimating metalenses on cyclo-olefin polymer and polyimide films using super inkjet printing. The fabricated metalenses are composed of double-sided printed metal patches on dielectric films, enabling simultaneous control of the electric and magnetic fields while maintaining an optically thin structure. The printed terahertz collimating metalenses fabricated on cyclo-olefin polymer and polyimide films enhance the directivity of a resonant tunneling diode oscillating at 0.312 THz to 2.29 and 1.46 times, respectively. Our results demonstrate advanced wavefront control of CW terahertz sources using inkjet-printed planar optical elements. The fabrication method for terahertz planar optical elements proposed in this paper will be a welcome contribution to terahertz flat optics in 6G and beyond wireless communication devices.