Size- and concentration-dependent of Rayleigh scattering properties of transparent TiO<sub>2</sub> nanohybrid polymer have been
systematically investigated. By utilizing the Rayleigh scattering technique, we can obtain the Rayleigh ratio of TiO<sub>2</sub>
nanohybrid polymer prepared with different concentrations of TiO<sub>2</sub>. We observed that these Rayleigh ratios are strongly
dependent on the size and concentration of the nanoparticles. The larger the size and concentration of nanoparticles is,
the larger the Rayleigh scattering is. Furthermore, this technique can be used to examine the saturation effect of Rayleigh
scattering observed at high input power, and evaluate the size uniformity of nanoparticles in nanohybrid polymer.
Recently there are many reports on the nonlinear optical (NLO) and electronics properties of semiconducting binary
nanocrystals such as CdSe, PbS and CdS. In the spectral regime where the photon energy (ħω) is less than the bandgap
(<i>E</i><sub>g</sub>), two photon absorption and two-photon-absorption-associated processes are dominant mechanisms. When ħω > <i>E</i><sub>g</sub>,
however, saturable absorption due to band filling mechanism plays an important role. However, very few results related
to optoelectronics properties on ternary nanocrystals are reported. Here, we present large NLO properties of ternary
nanocrystals such as AgInS<sub>2</sub> quantum dots (QDs) and AgInSe<sub>2</sub> nanorods (NRs) studied by femtosecond laser pulse at 780 nm. By employing Z-scan and transient absorption techniques, the third-order susceptibility of AgInS<sub>2</sub> QDs and
AgInSe2 NRs has been measured to be as large as 10<sup>-8</sup> esu. The origin of NLO properties in AgInS<sub>2</sub> QDs is due to two
photon absorption. While the NLO behavior of AgInSe<sub>2</sub> NRs is mainly contributed by saturation in the nonlinear
absorption and optical Kerr nonlinearity with a recovery time determined to be a few ten picoseconds.
Recently, ultrafast nonlinear optical responses of single-wall carbon nanotubes (SWCNTs) in suspensions and in films have been investigated intensively. Transient photobleaching has been observed with femtosecond laser pulses at photon energies of 0.8 ~ 1.1 eV (wavelengths = 1100 ~ 1550 nm), resonant with the lowest interband transitions of semiconducting SWCNTs. Here, we report both absorptive and refractive nonlinearities in a film of multiwalled carbon nanotubes (MWCNTs) grown mainly along the direction perpendicular to the surface of quartz substrate. Such MWCNT films are prepared by a method of plasma enhanced chemical vapor deposition. By employing Z-scans with 180-fs laser pulses at wavelengths ranging from 720 to 1550 nm, we have observed that both absorptive and refractive nonlinearities are of negative. More importantly, the degenerate pump-probe measurement reveals an ultrafast recovery time of ~ 1 ps. In addition, we also present a demonstration that the ultrafast nonlinear optical properties can be manipulated by a hybrid system in which MWCNTs are coated with ZnO nanoparticles. At wavelengths of interest, it is known that ZnO possesses three-photon (or four-photon) absorption, which is of positive sign and can be used to balance off the negative nonlinearity of MWCNTs.
We report the optical limiting response of carbon nanoparticle colloids in different organic solvents. The carbon nanoparticles were prepared by Nd:YAG laser ablation of carbon target immersed in ethanol. Optical limiting properties towards 532 and 1064 nm wavelengths were measured with a 7-ns pulsed Nd:YAG laser. Strong optical limiting effect was detected for the carbon nanoparticle colloids within a solvent having low thermal conductivity. The limiting effect at 532 nm is stronger than that at 1064 nm. Possible mechanisms of optical limiting were discussed.