Describing third-order nonlinear optical properties of nanocrystalline porous silicon using Bruggeman model

In this paper, a comparison between third order effective nonlinear optical susceptibility of nanoporous Si (nPS), predicted by Bruggeman model, and experimental value of chi
_nPS
obtained with the reflection Z-Scan technique is presented. Our nPS samples were realized by electrochemical etching of bulk silicon in hydrofluoric acid (HF). The Si fill fraction and the thickness of the layer can be controlled by the current density, the duration of etching and the concentration of HF. In our case, the fill fraction of nPS sample is f
_Si
~ 0.2 and the band gap is ~ 2 eV