Optical Nonlinear Properties of Water-Soluble CdSeS quantum dot

摘要

The optical nonlinear properties of water-soluble quantum dot have been investigated by using the Z-scan technique with the second-harmonic generation(532nm) of the mode-locked Nd: YAG laser. According to the absorption spectrum, it is concluded that the absorption at 532nm is the two photon absorption process. On the basis of the open-aperture Z-scan measurements, the TPA coefficients and corresponding TPA cross sections for the four different pulse irradiances are presented. The experimental results show the water-soluble CdSeS quantum dot possesses large two-photon absorption (TPA) at 532nm wavelength. In addition, we also calculate the nonlinear refractive index and third-order nonlinear susceptibility. It is found that the two photon absorption coefficients depend on the intensity of the laser and the nonlinear refractive index is independent of the laser irradiance. All the results indicate that it is possible for CdSeS quantum dot be a promising material for biological fluorescence label and imaging.