  The negatively charged silicon monovacancy $V_{Si}^-$ in 4H-silicon carbide
(SiC) is a spin-active point defect that has the potential to act as a qubit or
quantum memory in solid-state quantum computation applications. Photonic
crystal cavities (PCCs) can augment the optical emission of the $V_{Si}^-$, yet
fine-tuning the defect-cavity interaction remains challenging. We report on two
post-fabrication processes that result in enhancement of the $V_1^{'}$ optical
emission from our 1-dimensional PCCs, indicating improved coupling between the
ensemble of silicon vacancies and the PCC. One process involves below bandgap
illumination at 785 nm and 532 nm wavelengths and above bandgap illumination at
325 nm, carried out at times ranging from a few minutes to several hours. The
other process is thermal annealing at $100^o C$, carried out over 20 minutes.
Every process except above bandgap irradiation improves the defect-cavity
coupling, manifested in augmented Purcell factor enhancement of the $V_1^{'}$
zero phonon line at 77K. The below bandgap laser process is attributed to a
modification of charge states, changing the relative ratio of $V_{Si}^0$ (dark
state) to $V_{Si}^-$ (bright state), while the thermal annealing process may be
explained by diffusion of carbon interstitials, $C_i$, that subsequently
recombine with other defects to create additional $V_{Si}^-$s. Above bandgap
radiation is proposed to initially convert $V_{Si}^{0}$ to $V_{Si}^-$, but also
may lead to diffusion of $V_{Si}^-$ away from the probe area, resulting in an
irreversible reduction of the optical signal. Observations of the PCC spectra
allow insights into defect modifications and interactions within a controlled,
designated volume and indicate pathways to improve defect-cavity interactions.
