  Silicon vacancies in silicon carbide have been proposed as an alternative to
nitrogen vacancy centers in diamonds for spintronics and quantum technologies.
An important precondition for these applications is the initialization of the
qubits into a specific quantum state. In this work, we study the optical
alignment of the spin 3/2 negatively charged silicon vacancy in 6H-SiC. Using a
time-resolved optically detected magnetic resonance technique, we coherently
control the silicon vacancy spin ensemble and measure Rabi frequencies and
spin-lattice relaxation time of all three transitions. Then to study the
optical initialization process of the silicon vacancy spin ensemble, the
vacancy spin ensemble is prepared in different ground states and optically
excited. We describe a simple rate equation model that can explain the observed
behaviour and determine the relevant rate constants.
