THz Thin Film Sensing with Labyrinth Metasurface Absorber

In this work, a labyrinth metasurface sensor operating in the Terahertz (THz) band is presented. The strong electric field confinement leads to an excellent performance of this structure as thin film sensor. The sensing capability of the designed structure is numerically and experimentally measured. As the analyte (i.e. the substance sensed) thickness is increased, a frequency shift of the fundamental resonance is observed. Two different designs are studied both of them with excellent performance. An experimental average Figure of Merit (FOM) of 5093 (mm•RIU)^-1 and 3111 (mm•RIU)^-1 is obtained for both designs, improving the results found in the literature for structures fabricated with the same manufacturing techniques. Next, a numerical study of the behavior of the metasurface depending on the polarization characteristics is presented. The polarization angle of the incident E-field is varied between 0° and 90° showing a stable response in terms of the reflection coefficient. This aspect presents great advantages for thin film sensing, and could be extended to biological sensing in the future.