Numerical simulated reflectivities in ranges of [0°, 3°] and [18°, 20°], respectively. The parameters in the simulation are given as follows: the silver film thickness is d_ag = 30 nm, the thickness values of the two layers in the guiding layers are d_glass = 30 mm and d_air = 0.7 mm, respectively, the incident wavelength is 785 nm, and the dielectric constants are ε_ag = −23.82 + 1.78i, ε_glass = 2.283, respectively.