Abstract

We consider a hybrid optomechanical system composed of an ensemble of identical rare earth ions embedded in a bulk crystal, and coupled to internal strain. We evidence the generation of a mechanical response within this hybrid system under resonant atomic excitation, which we find to be driven by two fundamental contributions: First, a conservative backaction force coined as piezo-orbital, coming along with the promotion of the atoms in their excited state. This effect is expected in all impurity-doped crystals and reflects the interaction between the ions’ orbital shape and the crystal field of their host matrix. The second contribution corresponds to a dissipative, photothermal backaction force associated with the non-radiative relaxation dynamics of the rare-earth ions. The two components are identified by means of a spatio-temporal mapping of the mechanically non-resonant optomechanical response in the bulk crystal. The optically resonant nature of the two effects and their fundamental connection to the internal atomic state dynamics are quantitatively confirmed.

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