  Silicon is an ideal material for on-chip applications, however its poor
acoustic properties limit its performance for important optoacoustic
applications, particularly for Stimulated Brillouin Scattering (SBS). We
theoretically show that silicon inverse opals exhibit a strongly improved
acoustic performance that enhances the bulk SBS gain coefficient by more than
two orders of magnitude. We also design a waveguide that incorporates silicon
inverse opals and which has SBS gain values that are comparable with
chalcogenide glass waveguides. This research opens new directions for
opto-acoustic applications in on-chip material systems.
