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Steady state florescence and three-photon-absorption-induced upconversion fluorescence of two fluorene-based derivatives with different electron donors were investigated. The upconversion fluorescence intensity is cubic with the input intensity. The electron donors have great impact on the upconversion fluorescence property. The transition processes of the two molecules were investigated with TD SCF/DFT theory methods, the results of theory and experiments accord well with each other.

Three-photon absorption (3PA) cross-section dependence on structure property for two highly conjugated molecules is reported. 3PA cross-sections of the molecules were measured through an optimized method. A 37-fold enhancement was obtained by coupling. The mechanism of this significant enhancement in 3PA cross-section was investigated by density functional theory (DFT) and configuration interaction singles (CIS) method with 6−311 G basis sets. The influence of molecular structure property on the 3PA cross-section is discussed micromechanically. The experimental and theoretical results demonstrate that the coupling effect by C9=C9′ double bond is the most definitive factor for the enhancement behavior.

We investigate the third-order nonlinear optical properties of six novel fullerene derivatives under picosecond laser excitation by Z-scan technique. The experimental results reveal that all the derivatives have very large nonlinear absorption coefficient under 532 nm pulses excitation and great third-order nonlinear refraction index under 1064 nm pulses excitation. The molecular second hyperpolarizabilities are obtained from the experimental results.

Riboflavin is employed as the photosensitizer of a novel photopolyrner material for holographic recording, This material has a broad absorption spectrum range (More than 200nm) due to the addition of this dye. The experimental results show that our material has high diffraction efficiency and large refractive index modulation. The maximum diffraction efficiency of the photopolymer is about 56%. The digital data pages are stored in this medium and the reconstructed data page has a good fidelity, with the bit-error-ratio of about 1.8 X 10(-4). it is found that the photopolymer material is suitable for high-density volume holographic digital storage.

Three-photon absorption coefficient obtained by current nonlinear transmittance method has large fitting error because of uneven laser radiation distribution. Relatively small three-photon absorption cross section values of present nonlinear molecules restrict their practical applications. In this paper, an accurate three-photon absorption coefficient fitting method is presented, which is applicable for a variety of laser distributions. A fluorene-based derivative, 2, 7-bis(4-methoxyphenylacetylene)-9-thoine-fluorene, is synthesized. Apparent three-photon-absorption-induced optical stabilization effect is shown.