Fig. 1. Schematic diagram of structure model with two-dimensional cross profile

Fig. 2. Frequency bands and Q factors for different duty ratios η at f=0.1. (a) η=0.4; (b) η=0.5; (c) η=0.6; (d) BIC and resonant mode fields

Fig. 3. Frequencies and Q values of ΓA and ΓB varying with f for d=0. (a) η=0.4; (b) η=0.5; (c) η=0.6

Fig. 4. Frequencies and Q values of ΓA and ΓB modes varying with d for f=0.355. (a) η=0.4; (b) η=0.5; (c) η=0.6; (d) four mode field diagrams near the first degeneracy point in Fig. 4(a)

Fig. 5. Transmittance spectra varying with d for f=0.355 and different η. (a) η=0.4; (b) η=0.5; (c) η=0.6