Dynamical back-action at 5.5 GHz in a corrugated optomechanical beam

We report on the optomechanical properties of a breathing mechanical mode oscillating at 5.5 GHz in a 1D corrugated Si nanobeam. This mode has an experimental single-particle optomechanical coupling rate of |g o, OM | = 1.8 MHz (|g o, OM |/2π = 0.3 MHz) and shows strong dynamical back-action effects at room temperature. The geometrical flexibility of the unit-cell would lend itself to further engineering of the cavity region to localize the mode within the full phononic band-gap present at 4 GHz while keeping high g o, OM values. This would lead to longer lifetimes at cryogenic temperatures, due to the suppression of acoustic leakage.