Three novel nonlinear chromophores with symmetric D-π-D molecular structure and extended conjugated length were synthesized. Solvatochromism analysis shows great symmetric intramolecular charge transfer occurring in chromophores by the enhancement in the dipole moment between the ground and excited states. The properties of optical power limiting induced by three-photon absorption （3PA） are demonstrated. Large 3PA coefficients and the corresponding molecular cross sections as high as 10^-74 cm^6s^2 were obtained for nanosecond laser pulses at 1.06μm from nonlinear transmission measurements.
Fu-quan GuoXiao-lao SunHao LiangZhi-yuan HuQi-jin ZhangHai Ming
The sol-gel transition process of PMMA/SiO2 hybrid materials was first studied by means of the dynamic torsional vibration method. The different stages of the transition can be described by the change of torque. The temperature-dependent measurement of the gel time（ tg ） gives the possibility to determine the apparent activation energy.（ Ea ） of this transition according to Flory＇s gelation theory. The non-equilibrium thermodynamic fluctuation theory was used to predict the transition behavior. The isothermal transition experiments on hybrid sols with different TEOS（tetraethyl orthosilicate） contents were carried out. The results show that the Ea of a hybrid sol is higher than that of a non- hybrid sol of a TEOS-water-ethanol system. The increasing of TEOS content in a hybrid sol has no obvious effect on the Ea value, but it can enhance the sol-gel .reaction rate.
Rhodamine 6G-doped step-index polymer optical fiber is fabricated. The characteristics of the amplification of rhodamine 6G-doped step-index polymer optical fiber amplifier have been studied. The high-gain optical amplification with a tunable wavelength range from 585 to 613 nm is obtained in a step-index polymer optical fiber doped with rhodamine 6G at 10-ppm level, which can be used for broadband amplifiers and tunable lasers.
A novel organic chromophore 4, 4＇-bis（9-carbazyl-trans-styryl）-biphenyl （BCSBP） has been synthesized and characterized by IHNMR and elemental analysis. Three-photon absorption（3PA） induced upconvention fluorescence was observed and large 3PA cross section as high as 10^-74 cm^6 s^2 was obtained for nanosecond laser pulses at 1064 nm from optical limiting measurements.
