Fig. 1. (a) Schematic diagram of one-dimensional metallic nano-slit arrays structure on sapphire substrate. The whole structure is immersed in water; (b) the reflection spectrum at normal incidence; (c)(d) the normalized magnetic field intensity distributions corresponding to the dip 1 and dip 2, respectively

Fig. 2. Analysis of the phase difference between neighboring magnetic surface plasmon resonances in one-dimensional metallic nano-slit arrays in (a) water and (b) substrate. The red arrows represent the incident light

Fig. 3. 2D Reflection spectra of the structure in the range of and . (a) Three dashed lines , , and represent different orders of magnetic surface plasmon coherence corresponding to the interface between metal and water, respectively. Two solid lines and represent different orders of coherence corresponding to the interface between metal and substrate; (b) positions of fixed wavelength and fixed incident angle are marked by vertical and horizontal dashed lines in 2D spectrum, respectively

Fig. 4. (a) Angle-resolved reflection spectrum at a fixed incident wavelength of 1150 nm. (b) The four graphs show the normalized magnetic field intensity distributions corresponding to the four dips A, B,C and D appearing in (a), respectively. Black arrows represent the Poynting vectors

Fig. 5. (a) The angle-resolved reflectance spectrum obtained by changing the refractive index of the upper medium (n_w=1.33 ~ 1.53) with an interval of 0.05 at the wavelength of 1150 nm. (b) Dip position varying with the refractive index. (c) Reflection spectrum is obtained by changing the wavelength when is fixed at 5°. As the refractive index increases, both coherence dips are red-shifted. (d) The angle difference between dipA and dip B varying with the upper medium

Fig. 6. Sensing performance comparison in two conditions. Condition 1: the refractive index of the medium in the slit is the same as that of the upper medium; condition 2: the refractive index of the medium in the slit is fixed at 1.33