Fig. 1. Five-layer asymmetric waveguide structure

Fig. 2. The magnetic field distribution H_y of the five-layer asymmetric waveguide along the ydirection.(a) TM_0pmode; (b) TM₁mod; (c) TM₂ mode; (d) TM₃ mode

Fig. 3. Effective refractive index versus wavelength. (a) Real part of effective refractive index versus wavelength;(b) Imaginary part of effective refractive index versus wavelength [insets: Re(n_eff) and Im(n_eff) of the TM_0p mode]

Fig. 4. The average power density of the Gaussian beam normal incident on the xz plane at g = 2.5 μm

Fig. 5. Coupling efficiency of different modes

Fig. 6. Transmission spectra of different refractive indices. (a) z = 2.5 μm, TM_0pmode; (b) z = 2.5 μm, Superimposed mode;(c) z = 5 μm, TM_0p mode; (d) z = 5 μm, Superimposed mode