Fig. 1. Schematic diagram of a 2D VCM. The curvature is linearly changed as the boundary starting from zero curvature points to the neighboring maximum-curvature points.

Fig. 2. (a) Mode intensity spectrum and mode field patterns |Hz| of the (b) circular-like mode, (c) fundamental four-bounce mode, (d) first-order four-bounce mode, and (e) high-order hybrid mode.

Fig. 3. Q factors and wavelengths for deformed resonator from VCM to (a) microcircular resonator and (b) microsquare resonator.

Fig. 4. (a) Poincaré surface of sections (SOSs) of VCM; inset shows ray trajectories of two kinds of closed orbits with reflection times of 3000, which are marked by dots of the same color in the phase space. We zoom in on one of the droplets to show the details of the regular regions. (b) Top and droplet centers of the SOS; horizontal and vertical coordinate ranges are expressed on the left and bottom of each graph.

Fig. 5. Husimi projections of the (a) circular-like mode and (b) fundamental four-bounce mode. Insets show the field distributions |Hz| of both modes.

Fig. 6. (a) Wavelengths, Q factors, and (b) frequency differentials of circular-like and fundamental four-bounce modes versus the refractive index change of the dark-colored ring region.

Fig. 7. Frequencies of the circular-like and fundamental four-bounce modes versus VCM size.

Fig. 8. (a) Q factors of dual mode versus waveguide rotating angles and field distributions of |Hz| for the circular-like modes with rotating angles of (b) 0° and (c) 27°, and for the fundamental four-bounce modes with rotating angles of (d) 27° and (e) 45°.