Figure 5. Characteristic spectral Brillouin line shapes and nonlinear coefficients obtained from both experiments and simulations.

(a,b) Spectrally resolved Stokes and anti-Stokes Brillouin lines shapes, respectively, for the m=3 resonance of w=3.8 μm BAM waveguide. The theoretical fit (red line) obtained using the line shape derived in Supplementary Note 2 are shown as red curves atop the experimental data (circles). (c) Normalized heterodyne signals measured by the RF power meter for w=3.8 μm. (d) Simulated contributions of radiation pressure (blue bar), ES forces (orange bar) and thermoelastic coupling (violet bar) to the total Brillouin non-linear coefficient (black bar) are numerically calculated for w=3.8 μm for a fixed phononic Q of 1,000. (e) Comparison between the experimentally obtained (pink circle) and the theoretically calculated (green bar) SBS gain coefficients when experimentally measured quality factor of each resonant mode is incorporated within simulations. (f) Measured Q-factor of each resonant mode versus frequency for each resonance of the w=3.8 μm BAM waveguide, corresponding to modes m=1,2,…7 identified in Fig. 2.