  We propose a scheme able to generate stationary continuous variable
entanglement between an optical and a microwave cavity mode by means of their
common interaction with a micro-mechanical resonator. We show that when both
cavities are intensely driven one can generate bipartite entanglement between
any pair of the tripartite system, and that, due to entanglement sharing,
optical-microwave entanglement is efficiently generated at the expense of
microwave-mechanical and opto-mechanical entanglement.
