  Piezoelectric optomechanical platforms present one of the most promising
routes towards efficient transduction of signals from the microwave to the
optical frequency domains. New device architectures need to be developed in
order to achieve the stringent requirements for building efficient quantum
transducers. In this work, we utilize the mechanical supermode principle to
improve the overall microwave to optical transduction efficiency, by
fabricating Lamb wave resonators that are hybridized with the mechanical
breathing modes of a rib waveguide in a suspended gallium arsenide (GaAs)
photonic integrated circuits (PIC) platform. Combining the strong elasto-optic
interactions available in GaAs with the increased phonon injection efficiency
enabled by this architecture, we demonstrate signal transduction up to 7 GHz,
and an increase in transduction efficiency by $\approx$ 25$\times$ for the
hybridized mode ($f_m\approx$ 2 GHz), using this approach. We also outline
routes for improving device performance to enable quantum transduction within
this platform.
