Fig. 1. (a) Schematic of the employed PPC lattice with a triangular lattice of air holes in a silicon slab. Inset: the reciprocal lattice of the PPC lattice. (b)–(d) Zoomed structures around the defect regions of the (b) D-, (c) L3-, and (d) H0-type PPC cavities. The initial positions and profiles of the air holes in the PPC lattice are denoted by dashed red circles.

Fig. 2. (a) Electric field distributions (Ex and Ey) of the fundamental resonant mode in a D-type cavity with D′=1.6r. (b) The Ey profiles of the resonant modes in D-, L3-, and H0-type cavities over the cavity centerline along the x direction (solid lines) and fitted curves calculated from the product of a Gaussian envelope function and a sinusoidal wave (dashed lines). (c) The Q factor, Vmode, Q/Vmode, and resonant wavelength of the fundamental resonant modes calculated from the D-type cavities with a varied D′.

Fig. 3. (a) Schematic structure of the cavity induced by cutting two air holes adjacent to the line defect of a PPC waveguide. The dashed red circles represent the initial profiles of the cut air holes. (b) The electric field distributions (Ex and Ey) of the fundamental resonant mode with D′=1.6r. (c) The Q factor, Vmode, Q/Vmode, and resonant wavelength of the fundamental resonant modes versus D′.

Fig. 4. (a) Schematic structure of the L3-type cavity with cut air holes at the cavity edge. The dashed red circles represent initial positions and profiles of the air holes in the PPC lattice. (b) The electric field distributions (Ex and Ey) of the fundamental resonant mode with D′=0.9r. (c) The Q factor, Vmode, Q/Vmode, and resonant wavelength of the fundamental resonant mode versus D′.