The features of nonlinear absorption during resonance one- and two-photon excitation of the basic exciton transition in colloidal CdSe/ZnS quantum dots |
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Authors: | V S Dneprovskii E A Zhukov M V Kozlova A M Smirnov T Wumaier |
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Institution: | 1. Department of Physics, Moscow State University, Moscow, 119991, Russia 2. Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi, China
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Abstract: | The features of the nonlinear absorption of CdSe/ZnS quantum dots (colloidal solution) in the case of resonant one- and two-photon excitation of the basic exciton transition by powerful ultra-short laser pulses were determined. In one-photon excitation, with an increasing intensity of impulses, a decrease in absorption (bleaching) is relayed by an increase in absorption, which is associated with the process of the filling of the states (saturation) of a two-level system with the lifetime of the excited state depending on the light intensity. The arising Fresnel or Fraunhofer diffraction of the laser ray that pass through a colloidal solution with a high concentration of quantum dots is associated with the formation of the transparency channel and self-diffraction of laser ray on an induced diaphragm. In two-photon excitation, the features of the nonlinear absorption and luminescence tracks (the dependence of luminescence intensity on distance) were explained by the influence, in addition to the two-photon absorption, of the processes that are responsible for the slower growth of nonlinear absorption and luminescence quenching at high intensities of laser pulses. |
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