Self focusing-self defocusing transformation in an organometalic fullerene-C₆₀ derivative

We studied the nonlinear refraction properties of an organometallic fullerene-C₆₀ derivative fac- and mer- [bis(1, 2-diphenylphosphino) ethane] (tricarbonyl)(η²-fullerene-C₆₀) chromium by using Z-scan method. We also investigated the nonlinear refraction behavior of exited-state nonlinear optical materials and the switching between self-defocusing and self-focusing caused by the refrangibility of high excited state based on rate-equation theory. The transformation intensity was worked out, and the experiment was simulated numerically. The theoretical results agrees well with the experimental data.