Electrically driven acousto-optics and broadband non-reciprocity in silicon photonics

Emerging technologies based on tailorable photon-phonon interactions promise new capabilities ranging from high-fidelity information processing to non-reciprocal optics and quantum state control. However, many existing realizations of such light-sound couplings involve unconventional materials and fabrication schemes challenging to co-implement with scalable integrated photonic circuitry. Here, we demonstrate direct acousto-optic modulation within silicon waveguides using electrically driven surface acoustic waves (SAWs). By co-integrating electromechanical SAW transducers with a standard silicon-on-insulator photonic platform, we harness silicon's strong elasto-optic effect to create travelling-wave phase and single-sideband amplitude modulators from 1 to 5 GHz, with index modulation strengths comparable to electro-optic technologies. Extending this non-local interaction to centimetre scales, we demonstrate non-reciprocal modulation with operation bandwidths of >100 GHz and insertion losses of <0.6 dB. This acousto-optic platform is compatible with complementary metal-oxide-semiconductor fabrication processes and existing silicon photonic device architectures, opening the door to flexible, low-loss modulators and non-magnetic optical isolators and circulators in integrated photonic circuits.