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Studying the nonlinearities in the resonant mode one may face thermo-optical effects due to sample overheating, occurring upon exposure to high-frequency repetition rate probing pulse. If present, thermo-optical contribution to the refractive index are extremely hard to separate from the electronic contribution. In order to obtain purely electronic non-linear change in refractive index and to avoid thermal effects we modify classic Z-scan method to operate with low probing laser pulse repetition rate of 1 Hz. In our work, we present results of a Z-scan measured non-linear refraction coefficient of colloidal PbS QDs of different sizes free from thermal contribution. Our measured values of nonlinear refractive index is in order of 10-16 cm2/W and independent on the QD concentration in the solution.
Keywords: Nanocrystals, quantum dots, lead sulfide, z-scan, non-linear refraction© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.