Multiphoton Absorption and Multiphoton Excited Photoluminescence in Transition Metal Doped ZnSe/ZnS Quantum Dots

Abstract

In the applications of semiconductor quantum dots in multi-photon bio-imaging, up-conversion lasing and three dimension data storage, the two-photon absorption (2PA), three-photon absorption (3PA) in ZnSe/ZnS and Cu- and Mn-doped ZnSe/ZnS quantum dots were systematically investigated. The transition metal doping not only enhances the quantum yields of semiconductor QDs, but also enlarges the 2PA and 3PA cross-sections in the interested range of photon energies. The later is mainly caused by the introduced new doping levels as well as defect energy levels by the incorporated transition metal ions. The transition metal doping provides a new approach to manipulate the MPA cross-sections other than the size in semiconductor QDs. With this approach, the tailoring of the MPA cross-sections and emission wavelength could be realized with the addition of dopant and tuning of QD size. Further more, an experimental methodology has also been developed and demonstrated to separate the 2PA and 3PA contributions in semiconductor QDs when the excitation photon energy is near half of the band gap.