Multi-photon absorption saturation

The total fluorescence intensity saturated around a few hundreds of mJ/cm2 which corresponds to the irradiation condition where the new plasma-like emission was observed. Above this value fluorescence intensity decreased, which is accompanied with the recovery of the relative intensity of excimer emissions. This means that a quite efficient deactivation channel of excitation intensity opens in this energy range, and the contribution of Si -Si annihilation is depressed. This suggests that fragmentation reactions to diatomic radicals are not induced by the annihilation process. Multi-photon absorption processes via the Si states and chemical intermediates should be involved, although no direct experimental result has as yet been obtained. 

As shown in our previous works [9, 10] saturation effects are of great importance for long-pulse (t> 100fs) multi-photon absorption processes. They lead to certain dependencies for the absorption cross section on the input intensity of tire incoming light. A sufficiently accurate estimation of the saturation intensities can be obtained making use of the following expressions ... 

The case (3 > 0, opposite to the previous one, can stem in nanocomposite media from reverse saturation of absorption (RSA), multi-photon absorption, or nonlinear scattering. It is of course of high interest for optical limiting applications. 

There are several classes of optical effects induced by an internal perturbation, such as saturation of absorption, coherent Raman spectroscopy, multi-photon absorption processes, coherent transient spectroscopy (see Table 0.3). Section 5.1 of this chapter deals with saturation of absorption and multi-photon absorption processes. Section 5.2 outlines the principles of coherent anti-Stokes Raman spectroscopy (CARS), Raman-induced Kerr effect spectroscopy (RIKES), four-wave mixing (FWM), and photon echo. 

Saturation of Absorption and Multi-Photon Absorption Processes... 

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