Brillouin light scattering spectroscopy of cavity optomechanical crystals

We present a detailed study of Brillouin light scattering (BLS) spectroscopy applied to phononic waveguides embedded within optomechanical crystal structures. By comparing numerical simulations with experimental spectra, we validate the capability of BLS to probe GHz mechanical modes, including acoustic slow modes at 6.7 GHz, in silicon-on-insulator platforms at room temperature. Our results highlight the potential of BLS to characterize mechanical dispersion, guided modes, and acoustic bandgaps in cavity optomechanics, where photons and phonons are colocalized. This work provides critical insights into the feasibility of leveraging hypersonic phonons for in-chip interconnects and integrated broadband communication systems.