Highly sensitive terahertz fingerprint sensing with high-Q guided resonance in photonic crystal cavity.

In order to solve the problem of low sensitivity and poor selectivity in biochemical sensing using terahertz technology, a new sensing scheme based on photonic crystal cavity structure is proposed. It is composed of two identical photonic crystal slabs, each of which consists of a square lattice of silicon-based cylindrical pillars on a silicon substrate. The geometric parameters of the cavity are optimized to obtain a guided resonance peak at 529.2 GHz with a high quality factor of 529. The detected object is located in the middle of cavity where the electric field is strongly localized and confined. The effective detection of lactose with only a few microns thick is taken as an example to demonstrate the sensing performance of this cavity. A distinct decrease in transmittance at resonance peak is observed. The sensitivity using our proposed cavity is 31 times higher than that of using a substrate. Moreover, the selectivity of this photonic crystal cavity for the target is also verified by using fructose as the non-target. These results show that the photonic crystal cavity has potential to be applied for fingerprint detection with high sensitivity as well as selectivity in terahertz sensing.