Novel fluorophore based on a multi-substituted olefin skeleton with enhanced three-photon absorption in the femtosecond regime.

A new multipolar fluorophore based on a multi-substituted olefin skeleton that possesses strong three-photon absorption and optical-limiting properties in the femtosecond regime has been designed and synthesized; this archetype suggests a new strategy to further optimize molecular structures toward enhanced nonlinear absorptivities based on known materials.

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.