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Abstract

Stimulated Brillouin scattering drives a coherent interaction between
optical signals and acoustic phonons and can be used for storing optical
information in acoustic waves. An important consideration arises when
multiple optical frequencies are simultaneously employed in the
Brillouin process: in this case, the acoustic phonons that are addressed
by each optical wavelength can be separated by frequencies far smaller
than the acoustic phonon linewidth, potentially leading to cross talk
between the optical modes. Here we extend the concept of Brillouin-based
light storage to multiple wavelength channels. We experimentally and
theoretically show that the accumulated phase mismatch over the length
of the spatially extended phonons allows each optical wavelength channel
to address a distinct phonon mode, ensuring negligible cross talk and
preserving the coherence, even if the phonons overlap in frequency. This
phase-mismatch for broad-bandwidth pulses has far-reaching implications
allowing dense wavelength multiplexing in Brillouin-based light storage,
multifrequency Brillouin sensing and lasing, parallel microwave
processing, and quantum photon-phonon interactions. (C) 2019 Author(s).