Simultaneous Measurement of Magnetic Field and Temperature Based on Magnetic Fluid-Infiltrated Photonic Crystal Cavity

A method for simultaneous measurement of magnetic field and temperature with high sensitivity and high precision was realized according to magnetic fluid (MF)-infiltrated photonic crystal cavity, where two different types of MF were, respectively, infiltrated into certain air holes adjacent to a waveguide to form two cascaded cavities. As the refractive index (RI) of MF is dependent on external magnetic field and temperature, the two independent resonant dips of cascaded cavities that can be simultaneously monitored at the output spectrum of the waveguide would all shift with the change of external magnetic field or temperature. Using finite-difference time-domain method, the RI sensitivity of the proposed cavity was firstly analyzed and optimized, and then the linear relationships between the shifts of two resonant wavelengths and external magnetic field/temperature were calculated. Finally, combined with the dual-wavelength matrix method, the magnetic field detection limit could reach to 1.333 × 10^-4 T with the uncertainty of ±0.22 × 10^-4 T (coverage factor k = 2) and detection range from 0 to 0.06 T. Simultaneously, the temperature detection limit could reach to 0.301 K with the uncertainty of ±0.051 K (k = 2) and detection range from 250 to 340 K.