A chip-integrated coherent photonic-phononic memory

TLDR

Coherent acoustic phonons in integrated circuits are attractive for linking radiofrequency and optical signals, accessing quantum regimes, and enabling advanced signal processing, but existing optomechanical resonators offer high quality factors yet limited bandwidth and single‑wavelength operation. This study experimentally demonstrates a coherent optical buffer in a planar waveguide by transferring optical information to an acoustic hypersound wave. Using stimulated Brillouin scattering, the authors coherently map optical data onto hypersound phonons and retrieve it via the reverse process, enabling multi‑wavelength operation in a planar waveguide. The device stores both phase and amplitude of optical signals with gigahertz bandwidth and operates at distinct wavelengths with negligible cross‑talk, outperforming resonator‑based memories that are restricted to a single wavelength.

Abstract

Controlling and manipulating quanta of coherent acoustic vibrations-phonons-in integrated circuits has recently drawn a lot of attention, since phonons can function as unique links between radiofrequency and optical signals, allow access to quantum regimes and offer advanced signal processing capabilities. Recent approaches based on optomechanical resonators have achieved impressive quality factors allowing for storage of optical signals. However, so far these techniques have been limited in bandwidth and are incompatible with multi-wavelength operation. In this work, we experimentally demonstrate a coherent buffer in an integrated planar optical waveguide by transferring the optical information coherently to an acoustic hypersound wave. Optical information is extracted using the reverse process. These hypersound phonons have similar wavelengths as the optical photons but travel at five orders of magnitude lower velocity. We demonstrate the storage of phase and amplitude of optical information with gigahertz bandwidth and show operation at separate wavelengths with negligible cross-talk.Optical storage implementations based on optomechanical resonator are limited to one wavelength. Here, exploiting stimulated Brillouin scattering, the authors demonstrate a coherent optical memory based on a planar integrated waveguide, which can operate at different wavelengths without cross-talk.