High-sensitivity labyrinth metasurface working at THz for thin-film sensing

In this work a so-called labyrinth metasurface sensor working at the terahertz (THz) band is presented. The intricate geometry of the design leads to a high electric field confinement in all the structure surface, leading to ultrasensitive performance for thin-film sensing applications. The structure is coated with extremely thin analytes with thicknesses varying from h
_a
= 24 nm to h
_a
= 345 nm of tin dioxide (SnO
₂
) and its sensing capabilities are numerically and experimentally evaluated. Increasing the analyte thickness leads to a maximum redshift of 8 GHz at the resonance frequency. An average measured sensitivity of 12744.4 GHz/mm. RIU and a measured average FOM of 606.9 (mm.RIU) -1 are obtained, improving previous results found in the literature for designs that have been fabricated with the same manufacturing techniques. The great results obtained can lead to clear advantages for other type of sensing applications, where samples in a thin-film form become essential, such as biological sensing.