Strong Mechanical Modulation of Nitrogen-Vacancy Center Excited States

We study the resonant optical transitions of a single nitrogen-vacancy (NV) center under a strong mechanical drive in the resolved sideband regime. The NV center’s excited orbital states are strain-coupled to a monolithic, gigahertz-frequency diamond mechanical resonator, which dresses its resonant optical transitions with multiple orders of coherent Raman sidebands. Our study reveals all three symmetries of electron-phonon interactions, which both shift and mix the two excited-state orbital branches, E_x and E_y. Furthermore, we demonstrate Autler-Townes splitting of the orbital levels when a multiple of the mechanical drive frequency is placed in resonance with the E_x, E_y orbital splitting. Finally, we discuss the applications of strong mechanical driving to engineer NV center orbital states. These experiments serve as a model system for the study of a strongly-driven quantum system, and help lay the groundwork for the growing field of quantum acoustics.