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

The light emitting properties of nanostructured silicon (Si) have been intensively investigated due to its potential in optoelectronics. In this work, we present a comparison between third order effective nonlinear optical susceptibility of nanoporous Si (nPS), predicted by Bruggeman model, and experimental value of χ nPS (3) obtained with the reflection Z-Scan technique. 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 [1,2]. In our case, the fill fraction of nPS sample is ƒ Si ∼ 0.2 and the band gap is ∼ 2 eV.