Terahertz refractive index sensor based on the guided resonance in a photonic crystal slab

The optical properties of a photonic crystals slab (PCS) are highly sensitive to environmental variation. PCS thus are an attractive platform for sensing application. We numerically demonstrate a terahertz refractive index sensor based on the guided resonance in a two-dimensional PCS. The PCS consists of a square lattice of air holes in a silicon slab fabricated on a quartz substrate. By varying each structural parameter systematically, we study the dependence of the resonance located around 0.508 THz on the structural parameters of PCS, and then optimize the structural parameters of PCS for a higher sensitivity. We apply the PCS sensor to detect the refractive index of analytes. The sensitivity of the sensor reaches 23.08 GHz/RIU for the resonance located around 0.508 THz. Our results provide insight into the future terahertz spectroscopy for sensing detection.