Multi-photon excitation properties of CdSe quantum dots solutions and optical limiting behavior in infrared range

Multi-photon absorption and excitation properties of CdSe quantum dots in hexane with different dot-sizes have been investigated. The two- and three-photon absorption (2PA and 3PA) coefficients were measured by using ∼160-fs laser pulses at wavelengths of ∼775-nm and ∼1300-nm, respectively. The dependence of one-, two- and three-photon induced fluorescence spectra as well as their double-exponential decay on the dot-sizes was studied. Based on the fluorescence emission spectra and temporal decay constants for a given sample solution excited by one-, two-and three-photon absorption, it can be concluded that the transition pathways for fluorescence emission and decay under one-, two- and three-photon excitation are nearly identical. The optical power limiting capabilities based on 2PA and 3PA mechanisms are demonstrated separately. In addition, a saturation behavior of 3PA at ∼1300 nm was observed.