Two-photon-enhanced three-photon absorption in transition-metal-doped semiconductor quantum dots

Abstract

We report the observation of two-photon-enhanced three-photon absorption (3PA) in transition-metal-doped semiconductor quantum dots (d-QDs) in the near-infrared spectral region. Due to the degeneracy between two-photon transitions to the states of metal ions inside the bandgap and three-photon transitions to the excitonic state, the 3PA cross-section is greatly enhanced in comparison with the predictions by the 3PA theory derived under the four-band approximation. Together with the enhancement in their photoluminescence, such an enhancement mechanism is highly desirable in the design and optimization of fluorescent d-QDs for potential applications based on three-photon-excited fluorescence. © 2009 IOP Publishing Ltd.