SATURATION OF OPTICAL-TRANSITIONS IN QUANTUM DOTS AND WIRES OF POROUSSILICON

The bleaching bands have been observed in the time-resolved nonlinear transmission spectra of porous silicon. The increase of transmission a t discrete frequencies has been attributed to a saturation of optical transitions between the energy levels of electrons and holes spatially confined within quasi-zero-dimensional (quantum dots) and quasi-one-d imensional (quantum wires) nanostructures. The results of independent measurements using transmission electron microscopy have confirmed the existence of quantum dots and wires of corresponding size. The slowed -down energy relaxation from upper to lower levels of size quantizatio n compared with intraband relaxation in the bulk have been observed in the cooled (80K) platelets of porous silicon.