  In this work, we show that reversible photodegradation of Disperse Orange 11
doped in PMMA is not due to dye diffusion - a common phenomenon observed in
many dye-doped polymers. The change in linear absorbance due to
photodegradation of the material shows an isobestic point, which is consistent
with the formation of a quasi-stable damaged species. Spatially-resolved
amplified spontaneous emission and fluorescence, both related to the population
density, are measured by scanning the pump beam over a burn mark. A numerical
model of the time evolution of the population density due to diffusion is
inconsistent with the experimental data suggesting that diffusion is not
responsible.
