Study of coupling Tamm/Fano resonant states in one-dimensional photonic crystals comprising magnetic fluid for detecting weak magnetic fields

In this research, unconventional coupling of Tamm/Fano states was studied as a magnetic field sensor through a one-dimensional photonic crystal (1D PC) comprising a magnetic fluid. Thus, the magnetic field PC sensor is configured as [prism/Ag/cavity/(TiO<sub>2</sub>/CaF<sub>2</sub>)<sup>N</sup>]. In this regard, the cavity layer in this structure is filled with a magnetic fluid of sodium iodide (NaI). This magnetic cavity layer is sandwiched between a thin metallic film of Ag and multilayers of (TiO<sub>2</sub>/CaF<sub>2</sub>), thereby allowing this sensor to be very sensitive to any change in the applied magnetic field. The reflectance spectrum is analyzed based on the fundamentals of the transfer matrix method (TMM). In addition, all sensor parameters have been optimized to get the optimal conditions for the sensor performance. Moreover, numerical results showed that changing the intensity of the external applied magnetic field has a significant effect on the refractive index of the magnetic fluid and observed significant shifts in the position of the localized Tamm/Fano modes. Finally, different performance parameters are calculated, among them, a superb sensitivity is obtained with the value of 1500 nm/RIU at a magnetic field of just 50 Oe, which recommends this magnetic sensor as a good candidate in numerous magnetic applications.