Fig. 1. Schematic diagram of scattered light spectrum

Fig. 2. Energy level diagram of Brillouin scattering process

Fig. 3. Basic structure of Brillouin fiber optical gyroscope

Fig. 4. Gas Brillouin laser^[13]. (a) Schematic diagram of laser structure; (b) spontaneous and stimulated Brillouin scattering spectra

Fig. 5. Superfluid Brillouin laser^[46]. (a) Backward Brillouin scattering process in superfluid optomechanical resonator; (b) schematic illustration of the Brillouin interaction in superfluid system; (c) SBS peak power versus pump laser power; (d) SBS spectra

Fig. 6. As₂S₃-doped Brillouin fiber laser^[58]. (a) Experimental setup of Brillouin fiber laser; (b) output spectra with different coupling devices

Fig. 7. Brillouin microcavity laser^[75]. (a) Schematic diagram of microcavity; (b) pump, resonator spectra and Brillouin gain spectrum

Fig. 8. Typical whispering gallery mode optical microcavities. (a) Microcolumn cavity^[106]; (b) microsphere cavity^[107]; (c) microtoroid cavity^[68]

Fig. 9. Micro optical gyroscope based on Brillouin scattering. (a) Optical gyroscope based on SBS with SiO₂ microcavity^[82]; (b) optical gyroscope based on SBS with Si₃N₄ waveguide^[7]

Fig. 10. Brillouin optical gyroscope based on EP. (a) Enhanced sensitivity via EP^[121]; (b) Brillouin micro optical gyroscope based on EP^[79]

Fig. 11. Schematic of a PT-symmetric laser gyroscope system^[81]