  Silicon vacancy centers in silicon carbide are promising candidates for
storing and manipulating quantum information. Implementation of fast quantum
gates is an essential requirement for quantum information processing. In a low
magnetic field, the resonance frequencies of silicon vacancy spins are in the
range of a few MHz, the same order of magnitude as the Rabi frequencies of
typical control fields. As a consequence, the rotating wave approximation
becomes invalid and nonlinear processes like the absorption and emission of
multiple photons become relevant. This work focuses on multi-photon transitions
of negatively charged silicon vacancies driven by a strong RF field. We present
continuous-wave optically detected magnetic resonance (ODMR) spectra measured
at different RF powers to identify the 1-, 2-, and 3-RF photon transitions of
different types of the silicon vacancy in the 6$H$-SIC polytype. Time-resolved
experiments of Rabi oscillations and free induction decays of these multiple RF
photon transitions were observed for the first time. Apart from zero-field
data, we also present spectra in magnetic fields with different strength and
orientation with respect to the system's symmetry axis.
