Three-photon absorption in semiconductor quantum dots: Experiment

Abstract

The four-band model, derived under the effective-mass approximation for cubic semiconductor quantum dots (QDs), is compared with experimental measurements on frequency degenerate three-photon absorption (3PA) in CdSe QDs and ZnS QDs. Qualitatively, the model provides the correct prediction on the magnitude of the 3PA cross-sections, which are in the range from 10 -79 to 10-77 cm6s2photon -2 in the light frequency region of interest. More noticeably, the theoretical conclusion of an increasing tendency in the 3PA cross-sections with increasing dot-size is in agreement with the experiment. The discrepancy is also found for smaller QDs (dot-radius is less than one-third of the exciton Bohr radius), which is attributed to neglecting the mixing among the three valence bands in the theory. © 2008 Optical Society of America.