Summary: the magnitude of the gain. Thus, the delay
time of 0.5 s observed in Fig. 4 increases to
12 s at Eo 46 V/ m. Furthermore, the use
of additional polymer layers will not decrease
the threshold for oscillation noticeably un-
less an index-matching liquid is used to re-
duce the reflection losses accordingly. Once
oscillation has been achieved, however, the
PC reflectivity will increase significantly
faster with Eo for a larger multilayer stack.
Finally, predicting the threshold for oscilla-
tion or the value of R from measurements of
two-beam coupling gain is not a simple mat-
ter. Recent work has shown that these poly-
mers benefit from gain enhancement due to
very slow motion of the index grating, which
means that the cavity beam is expected to be
frequency-shifted from the pumping beam.
This complicates the theoretical analysis to a
level beyond the scope of this report (25).