  We demonstrate optically induced switching between bright and dark charged
divacancy defects in 4H-SiC. Photoluminescence excitation and time-resolved
photoluminescence measurements reveal the excitation conditions for such charge
conversion. For an energy below ~1.3 eV (above ~950 nm), the PL is suppressed
by more than two orders of magnitude. The PL is recovered in the presence of a
higher energy repump laser with a time-averaged intensity less than 0.1% that
of the excitation field. Under a repump of 2.33 eV (532 nm), the PL increases
rapidly, with a time constant ~30 $\mu$s. By contrast, when the repump is
switched off, the PL decreases first within ~100-200 $\mu$s, followed by a much
slower decay of a few seconds. We attribute these effects to the conversion
between two different charge states. Under an excitation at energy levels below
1.3 eV, V$_{Si}$V$_C$$^0$ are converted into a dark charge state. A repump
laser with an energy above 1.3 eV can excite this charged state and recover the
bright neutral state. This optically induced charge switching can lead to
charge-state fluctuations but can be exploited for long-term data storage or
nuclear-spin-based quantum memory.
