Magnetotransport‐Induced Non‐Contact Terahertz Detection of Weak Magnetic Fields in Optically Thin Frequency‐Agile Superlattice Metasurfaces

Abstract Magnetotransport, the magnetic field induced electron transport phenomenon through metals and semiconductors, has proven to be a useful technique to tailor the properties of electromagnetic radiation upon interaction with suitable materials and structures. Very recently, magnetotransport has become an important tool to dynamically tailor terahertz (THz) radiation and response of different optical devices. Based on these backgrounds, optically thin, subwavelength superlattice (with alternate arrangement of four metallic films: two non‐magnetic aluminum [Al] and two ferromagnetic nickel [Ni] films, having thickness of each film as 10 nm) metasurfaces are demonstrated, consisting of periodic arrays of asymmetric cut‐wire pair metasurfaces, which have a unique ability to exhibit both frequency and intensity modulation at its hybridized resonances when low‐intensity magnetic fields are applied. Such dynamic tuning characteristics are attributed to the combined effects of spin‐dependent THz magnetotransport in superlattice films, near‐field electromagnetic coupling between the resonators, and lattice mode coupling. Such THz metasurface is further employed for non‐contact detection of external magnetic fields in the range of 0–30 mT, while operating at the optically thin regime. The demonstrated scheme can further be extended to realize THz magneto‐spectroscopy toward devising state‐of‐the‐art photonic and magnetic technologies.