Anomalous optical bistability and robust entanglement of mechanical oscillators using two-photon coherence

We analyze the optical bistability and the entanglement of two movable mirrors coupled to a two-mode laser in a doubly resonant cavity. We show that in stark contrast to the usual red-detuned condition for observing bistability in single-mode optomechanics, the optical intensities exhibit bistability for all values of cavity laser detuning due to intermode coupling induced by two-photon atomic coherence. Interestingly, an unconventional bistability with “ribbon”-shaped hysteresis can be observed for a certain range of cavity laser detuning. We also demonstrate that the atomic coherence leads to a strong entanglement between the movable mirrors in the adiabatic regime. Surprisingly, the mirror–mirror entanglement is shown to persist for environment temperatures of the phonon bath up to 12 K using experimental parameters. © 2015 Optical Society of America