Fused-silica microstructural changes associated with localized $10.6\mu \mathrm{m}$ $\mathrm{C}{\mathrm{O}}_2$ laser heating are reported. Spatially resolved shifts in the high-frequency asymmetric stretch transverse-optic phonon mode of $\mathrm{Si}{\mathrm{O}}_2$ were measured using confocal Raman microscopy, allowing construction of axial fictive temperature $\left(T_f\right)$ maps for various laser-heating conditions. A Fourier conduction-based finite-element model was employed to compute on-axis temperature–time histories, and, in conjunction with a Tool–Narayanaswamy form for structural relaxation, used to fit $T_f\left(z\right)$ profiles to extract relaxation parameters. Good agreement between the calculated and measured $T_f$ was found, yielding reasonable values for relaxation time and activation enthalpy in the laser-modified silica.