  Using transmittance imaging microscopy we measure the wavelength dependence
of reversible photodegradation in disperse orange 11 (DO11) dye-doped
(poly)methyl-methacrylate (PMMA). The reversible and irreversible inverse
quantum efficiencies (IQEs) are found to be constant over the spectral region
investigated, with the average reversible IQE being $\overline{B}_\alpha= 8.70
(\pm 0.38)\times 10^5$ and the average irreversible IQE being
$\overline{B}_\epsilon= 1.396 (\pm 0.031)\times 10^8$. The large difference
between the IQEs is hypothesized to be due to the reversible decay channel
being a direct decay mechanism of the dye, while the irreversible decay channel
is an indirect mechanism, with the dye first absorbing light, then heating the
surrounding environment causing polymer chain scission and cross linking.
Additionally, the DO11/PMMA's irreversible IQE is found to be among the largest
of those reported for organic dyes, implying that the system is highly
photostable. We also find that the recovery rate is independent of wavelength,
with a value of $\overline{\beta}=3.88(\pm 0.47) \times 10^{-3}$ min$^{-1}$.
These results are consistent with the correlated chromophore domain model of
reversible photodegradation.
