Efficient infrared-upconversion luminescence in porous silicon: A quantum-confinement-induced effect

Abstract

We demonstrate for the first time that a porous silicon layer (PSL), which has a bright light-emission band in the range of 500--700 nm, exhibits a strong visible-range luminescence under the illumination of an infrared ultrashort pulsed laser. The dependence of integrated luminescence intensity on pump power shows that this is a third-order nonlinear optical effect. By comparing with UV-light-excited spectra of PSL and samples with low porosity which have inefficient luminescence, a possible explanation is proposed whereby the large nonlinear optical response is due to the quantum confinement effect.