Fig. 1. End face structure of MWBG and electric field distribution. (a) Structure; (b) electric field distribution along z direction; (c) electric field distribution along y direction

Fig. 2. Relation of Re(n_eff) and Im(n_eff) with the thickness of NaF layer

Fig. 3. Change rule of Im(n_eff), L, A_eff/A₀ and α_FOM with thickness of SiO₂ layer at different thicknesses of NaF layer

Fig. 4. (a) Structure of MWBG Bragg grating and (b) normalized electric field distribution in xz plane

Fig. 5. Reflection spectra of MWBG Bragg grating with different cycle numbers