Optomechanically induced transparency and self-induced oscillations with Bogoliubov mechanical modes

Bogoliubov mechanical modes have the mathematical form of two-mode squeezed states and can form in an optomechanical system in which two mechanical modes couple to an optical mode via respective red and blue sideband couplings. Analogous to optical parametric downconversion, these special mechanical excitations can enable the generation of phonon pairs as well as mechanical entanglement. Here we report experimental studies of Bogoliubov mechanical modes using a silica microsphere as a model three-mode optomechanical resonator. We have employed optomechanically induced transparency to characterize the effective optomechanical coupling of the Bogoliubov mode. Self-induced oscillations of the Bogoliubov mode further reveal that Stokes photons generated from blue sideband coupling are converted via red sideband coupling to phonons in another mechanical mode, demonstrating a key process for the optomechanical generation of phonon pairs. (C) 2014 Optical Society of America