THz optical response for H9N2 virus sample was characterized with transmission measurement through multi-resonance nano-antenna (Fig. 1d). The THz optical responses in terms of the changed values at three maximum transmittances (ΔT) and shifted resonance frequencies (Δf) are respectively plotted in Fig. 1e. As a meaningful frequency for further measurements, 1.4 THz was selected owing to its biggest changes in both ΔT and Δf values, implying the highest sensitivity. Further results with 1.4 THz single-resonance nano-antenna in Fig. 2 present that the viruses can be classified in terms of resonance frequency and decreased transmission ratio.Figure 2THz optical properties for various types of virus samples. (a) Normalized THz transmission spectra measured using the single-resonance nano-antenna without virus sample (black), and with selected three viruses, H1N1 (blue), H5N2 (cyan), and H9N2 (magenta). (b) FDTD simulation results of transmittances for the single-resonance nano-antenna and the three different model samples with various composition of dielectric constants (n and κ) are shown. Inset indicates a used geometry for simulation.