Yl. Xue et al., LARGE REFRACTIVE-INDEX AND INTERPARTICLE-INTERACTION-INDUCED NONLINEAR MODULATION IN DENSELY DOPED COMPOSITE-MATERIALS, IEEE journal of quantum electronics, 34(8), 1998, pp. 1380-1389
We have performed a study of the population dynamics in a composite, i
n which the active medium is densely doped, by considering the interpa
rticle interaction between the nearest neighboring active particles. A
model is presented to describe the nonlinear modulation induced by in
terparticle collective effects and upconversion in the resonantly enha
nced nonlinearity and its response to an input optical signal in such
a densely doped composite. The results show that the nonlinear refract
ive index can be greatly increased with unchanged or slightly reduced
transient response time. This is expected to have potential in lowerin
g the critical switching intensity of bistable switching devices witho
ut sacrificing switching speed. We examined two typical composites: fa
re-earth densely doped silica and perylimide-dye densely doped polymer
/glass composites. It is found that perylimide-dye densely doped polym
er/glass composite is more suitable for the switching application due
to its large nonlinear refractive index and fast response time at rela
tively low optical intensity.