  We examine how intense optical beams can penetrate deeply into highly
absorbing media by a non-linear, photo-bleaching process. The role of
stimulated recovery to the dye ground state can be important and is delineated.
This analysis of non-linear absorption processes is applicable in general to
situations where chromophores are irradiated, for instance in biology. We
examine the implications for the bending of cantilevers made of heavily
dye-loaded nematic photo-solids, that is nematic glasses and elastomers that
have large mechanical reactions to light. In particular we describe the bending
of cantilevers sufficiently absorbing that they would not bend if Beer's Law
were applicable. We quantify the role of optically-generated heat in
determining the mechanical response and conclude that in general it is minor in
importance compared with optical effects.
