We present progress towards the development of novel hybrid photonic-phononic oscillator technologies in both nanoscale silicon photonics and in fiber optic systems. These systems utilize traveling-wave photon-phonon couplings involving both stimulated Brillouin scattering processes (SBS). We explore numerous geometries that have enabled large forward-SBS processes in nanoscale silicon waveguides for the first time, and examine new approaches to achieving integrated Brillouin based signal processing.
We develop a general framework of evaluating slow-light performance using Stimulated Brillouin Scattering (SBS) in optical waveguides via the overlap integral between optical and elastic eigen-modes. We show that spatial symmetry of the optical force dictates the selection rules of the excitable elastic modes. By applying this method to a rectangular silicon waveguide, we demonstrate the spatial distributions of optical force and elastic eigen-modes jointly determine the magnitude and scaling of SBS gain coefficient in both forward and backward SBS processes. We further apply this method to inter-modal SBS process, and demonstrate that the coupling between distinct optical modes is necessary to excite elastic modes with all possible symmetries.