Magnetic field sensor based on evanescent wave coupling effect of photonic crystal slab microcavity

In this study, a novel magnetic field sensor (MFS) based on 2D photonic crystal slab (2D PCS) microcavity is proposed. Magnetic fluid film (MFF) covers the surface of PCS and is coupled to high-Q microcavity by evanescent field. The slight disturbance of the refractive index of MFF can cause a larger response of the microcavity optical local field. The magnetic field calibration is realized by measuring the output power of W1 waveguide. The finite difference time domain (FDTD) method was used to analyze and optimize the sensing characteristics of MFS. The simulation results show that the PCS magnetic sensor has good linearity and sensitivity. When the MFF with a thickness of L = 0.4 mu m completely covers the surface of PCS, the normalized sensitivity of W1 type waveguide-single microcavity coupling sensor structure can reach 2.52/T. Compared with the traditional photonic crystal magnetic sensor, the PCS magnetic sensor structure designed in this paper can adopt the existing MEMS processing technology and is easy to fabricate.