Fig. 2

Fabricated device and characterization of the topological cavity modes. a SEM image of a fabricated ‘Q’-shaped topological bulk cavity patterned on a GaAs wafer. The cavity is composed of a trivial PC (orange) encircled by a topological PC (purple). b Enlarged SEM image of the device. Black hexagons indicate unit cells of the PCs. c PL spectra collected from the device or substrate under high pump power. Three peaks correspond to the three topological states in the cavity, as shown in Fig. 1c and Figure S3. Bulk state 1 and bulk state 2 correspond to the dipole-like bulk state and the quadrupole bulk state, respectively