Modulation of Brillouin optomechanical interactions via acoustoelectric phonon-electron coupling.

Optomechanical Brillouin nonlinearities -- arising from the coupling between traveling photons and phonons -- have become the basis for a range of powerful optical signal processing and sensing technologies. The dynamics of such interactions are largely set and limited by the host material's elastic, optical, and photo-elastic properties, which are generally considered intrinsic and static. Here we show for the first time that it is feasible to dynamically reconfigure the Brillouin nonlinear susceptibility in transparent semiconductors through acoustoelectric phonon-electron coupling. Acoustoelectric interactions permit a wide range of tunability of the phonon dissipation rate and velocity, perhaps the most influential parameters in the Brillouin nonlinear susceptibility. We develop a Hamiltonian-based analysis that yields self-consistent dynamical equations and noise coupling, allowing us to explore the physics of such acoustoelectrically enhanced Brillouin (AEB) interactions and show that they give rise to a dramatic enhancement of the performance of Brillouin-based photonic technologies. Moreover, we show that these AEB effects can drive systems into new regimes of fully-coherent scattering that resemble the dynamics of optical parametric processes, dramatically different than the incoherent traditional Brillouin limit. We propose and computationally explore a particular semiconductor heterostructure in which the acoustoelectric interaction arises from a piezoelectric phonon-electron coupling. We find that this system provides the necessary piezoelectric and carrier response ($k^2\approx 6 \%$), favorable semiconductor materials properties, and large optomechanical confinement and coupling ($|g_0|\approx8000$ (rad/s)$\sqrt{\text{m}}$) sufficient to demonstrate these new AEB enhanced optomechanical interactions.