Enhanced photon-phonon coupling via dimerization in one-dimensional optomechanical crystals

We show that dimerization of an optomechanical crystal lattice, which leads to folding of the band diagram, can couple flexural mechanical modes to optical fields within the unit cell via radiation pressure. When compared to currently realized crystals, a substantial improvement in the coupling between photons and phonons is found. For experimental verification, we implement a dimerized lattice in a silicon optomechanical nanobeam cavity and measure a vacuum coupling rate of $g_0/2\pi=1.7MHz$ between an optical resonance at $\lambda_{c} = 1545nm$ and a mechanical resonance at 1.14GHz.