Light-sound interactions have long been exploited in various acousto-optic devices based on bulk crystalline materials. Conventionally, these devices operate in megahertz frequency range where the acoustic wavelength is much longer than the optical wavelength and a long interaction length is required to attain significant coupling. With nanoscale transducers, acoustic waves with sub-optical wavelengths can now be excited to induce strong acousto-optic coupling in nanophotonic devices. Here we demonstrate microwave frequency surface acoustic wave transducers co-integrated with nanophotonic resonators on piezoelectric aluminum nitride substrates. Acousto-optic modulation of the resonance modes at above 10 GHz with the acoustic wavelength significantly below the optical wavelength is achieved. The phase and modal matching conditions in this scheme are investigated for efficient modulation. The new acousto-optic platform can lead to novel optical devices based on nonlinear Brillouin processes and provides a direct, wideband link between optical and microwave photons for microwave photonics and quantum optomechanics.
Bibliographical noteFunding Information:
We acknowledge the funding support provided by the National Science Foundation (Award Number ECCS-1307601) and the Young Investigator Program (YIP) of AFOSR (Award Number FA9550-12-1-0338). Parts of this work were carried out in the University of Minnesota Nanofabrication Center, which receives partial support from NSF through NNIN programme, and the Characterization Facility, which is a member of the NSF-funded Materials Research Facilities via the MRSEC programme.
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