Spoofed surface plasmon polariton (SSPP) gap structure for high sensitivity bio-sensing in THz

We demonstrate enhanced sensitivity to refractive index (n) change in THz sensing by using the spoofed surface plasmon polariton (SSPP) architecture modified with gap blocks. The transmission peak as a function of n is significantly sharpened through the introduction of the additional cavity resonance, and such phenomenon is strongly dependent on the geometric dimensions of the block structure as well as the choice of probe frequencies. Non-invasive THz bio-sensing is a promising alternative to conventional tagging-based sensing schemes. In response to the growing demand for lower detection limit, our SSPP gap structure can effectively reduce the sample usage by enabling localized sample deposition within the gap cavity. The differentiation of DNA molecules with distinct binding states is demonstrated, where the conformational change of a thin layer (1μm) of immobilized DNA can lead to significant switching of the waveguide transmittance.