One-dimensional photonic crystal magnetic sensor design based on Bloch surface waves with high sensitivity and high figure of merit (FOM)

Abstract

A novel Bloch surface wave (BSW)-based one-dimensional photonic crystal magnetic sensor is proposed. Grating is used to realize the coupling of electromagnetic waves and BSW, and magnetic fluid is placed at the bottom of the sensor as the sensing medium. The sensing characteristics of a one-dimensional photonic crystal magnetic sensor were analyzed using the rigorous coupled wave analysis (RCWA) method. Based on the azimuthal interrogation method, the effects of different pole angles, defect layers, and structural parameters on sensitivity and figure of merit (FOM) were investigated. According to the drift of the resonance peak, the azimuthal sensitivity S = 9 °/mT, and the maximum detection sensitivity S = 14 °/mT were obtained (converted to refractive index sensitivity S = 6536 °/RIU and maximum detection sensitivity S = 9333 °/RIU). Excitingly, we found that the introduction of a defective layer can significantly improve the FOM (1925 RIU-1 to 69,444 RIU-1). The results show that the designed magnetic sensor structure has high sensitivity and a high FOM, which is an order of magnitude higher than other magnetic sensors. This work provides a guideline for the future development of one-dimensional photonic crystals in the field of weak magnetic sensing.