Specific features of resonant nonlinear absorption in colloidal solutions of CdSe/ZnS quantum dots

Nonlinear refraction coefficients and nonlinear absorption coefficients of colloidal solutions of CdSe/ZnS quantum dots (QDs) have been measured by the z-scan method. Resonant excitation was carried out by a Nd:YAG laser (λ = 532 nm, τ ∼ 7 ns). QDs have been chosen to correspond to different positions of the peak of the fundamental exciton absorption band with respect to the laser wavelength. The z-scan data are compared with the optical-limitation photodynamics data on CdSe/ZnS QD solutions. The obtained values of nonlinear absorption coefficients and their dependence on the QD size are interpreted in terms of the two-step mechanism of optical limitation.

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