We theoretically demonstrate the mechanically mediated optomechanically induced transparency and parametric amplification in a photonic molecules optomechanics, and study the coherent optical propagation in the system via choosing a suitable detuning of the pump field from optomechanical cavity resonance with manipulating the coupling strength of the two cavities.

The coupling strength of the two cavities is an important factor of the quantum channel, which can influence the width of the transparency window.

We further theoretically propose a mass sensor based on the photonic molecules optomechanical system, and the mass of external nanoparticles deposited onto the cavity can be measured conveniently by tracking the mechanical resonance frequency shifts due to mass changes in the probe transmission spectrum.

Compared with the optical mass sensor based on single-cavity optomechanics, the mass resolution is improved significantly due to the cavity-cavity coupling, which provides a new platform for on-chip applications in ultrahigh resolution sensor devices.