High Figure of Merit Magnetic Field Sensor Based on Photonic Crystal Slab Supporting Quasi Bound States in The Continuum

In this paper, a magnetic field sensor (MFS) with high figure of merit (FOM) is theoretically proposed, which is based on photonic crystal slab (PhCS) covered by magnetic fluid film (MFF). The PhCS consists of a two dimensionally periodic nanohole array introduced into a silicon slab. The large-sized nanohole is used to increase the area of light-matter interaction. By slightly breaking the symmetry of nanoholes, quasi bound states in the continuum (BIC) with Fano line shape is excited in the PhCS, which is sensitive to external magnetic field and has a high Q-factor. The effect of MFF thickness on the magnetic field sensitivity is investigated. Furthermore, high resonance amplitude of 0.97 and low limit of detection (LOD) of 6.1×10−5 T are achieved. Compared with the researches lately published, the sensor exhibits high Q-factor and high sensitivity. Therefore, we believe the proposed sensor will contribute to the lab-on-chip magnetic field detection system design.