  We report on what we believe is the first demonstration of an optically
activated cantilever due to photomechanical effects in a dye-doped polymer
optical fiber. The fiber is observed to bend when light is launched off-axis.
The displacement angle monotonically increases as a function of the distance
between the illumination point and the fiber axis, and is consistent with
differential light-induced length changes. The photothermal and
photo-reorientation mechanisms, each with its own distinct response time, are
proposed to explain the observed time dependence. The measured degree of
bending is consistent with a model that we have proposed which includes
coupling between photoisomerization and heating. Most importantly, we have
discovered that at high light intensity, a cooperative release of stress
results in cis-to-trans isomerization that yields a large and abrupt length
change.
