Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, 50-370 Wroclaw, Poland.
Nanoscale. 2013 Mar 21;5(6):2388-93. doi: 10.1039/c3nr33860f.
Wide wavelength range (550-1600 nm) measurements of nonlinear optical properties of ca. 5 nm CdS quantum dots (QDs) colloidal solution were performed using the Z-scan technique with femtosecond laser pulses at 1 kHz. Parameters characterizing nonlinear absorption and nonlinear refraction were determined. Nonlinear absorption has the character of a two-, three- and four-photon process depending on the wavelength range, with the values of the relevant coefficients peaking at 750 nm, 1200 nm and 1500 nm, respectively. The order of the nonlinear processes was confirmed by measurements of the integral luminescence intensity vs. input excitation intensity. Maxima of the multi-photon absorption bands correspond to the second absorption band of the QDs. The maximum value of the two-photon absorption cross-section σ2 was estimated to be 7.2 × 10(-47) cm(4) s per QD at 750 nm.
采用飞秒激光（1 kHz）的 Z 扫描技术，对约 5 nm 的 CdS 量子点（QD）胶体溶液的宽波长范围（550-1600nm）的非线性光学性质进行了测量。确定了表征非线性吸收和非线性折射的参数。非线性吸收具有双光子、三光子和四光子过程的特征，具体取决于波长范围，相关系数的峰值分别出现在 750nm、1200nm 和 1500nm。通过测量积分发光强度与输入激发强度的关系，证实了非线性过程的顺序。多光子吸收带的最大值对应于 QD 的第二吸收带。在 750nm 处，每个 QD 的双光子吸收截面σ2的最大值估计为 7.2×10(-47)cm(4)s。
