Self-phase modulation has been observed for ultrashort pulses of wavelength 800nm propagating through a 1 cm-long Ta2O5 rib waveguide. The associated nonlinear refractive index n2 was estimated to be 7.23x10-19 m2/W, which is higher than silica glass by more than one order of magnitude. Femtosecond time of flight measurements based on a Kerr shutter configuration show that the group velocity dispersion is small at a wavelength of 800 nm, confirming that dispersion may be neglected in the estimation of n2 so that a simplified theory can be used with good accuracy.

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Ta 2 O 5 waveguides offer great potential for high-density active photonic crystal circuits and their combination with rare-earth dopants for active devices is of interest for increasing their potential functionality. To this end, neodymium-doped Ta 2 O 5 rib waveguide lasers have been fabricated on an oxidized silicon wafer by RF sputtering and argon ion-beam milling and the first laser action in this material has been demonstrated. Lasing was observed at wavelengths between 1060nm and 1080nm and an absorbed pump power threshold of 87mW was obtained.

Broadband exciton dynamics in P3HT:PCBM blended film was observed by the femtosecond time-resolved photoluminescence sum-frequency technique. Onsager-Braun theory is applied to analyze the distribution of charge transfer radius at different energy levels. In our evaluation, the optimal diameter of P3HT fiber is about 14.3 nm for achieving the best exciton dissociation in P3HT:PCBM blended films. This technique can be readily used in the optimization of high-efficiency organic photovoltaics.