Optical power limiting in ensembles of colloidal quantum dots

The effect of power limiting for optical radiation at a wavelength of with a pulse duration of and operation threshold of is observed in ensembles of colloidal quantum dots (QDs). Using the -scanning method in an open-aperture scheme it is found that the power is limited mainly due to reverse saturable absorption caused by two-photon optical transitions that involve energy levels of photoluminescence centres, related to structural impurity defects in colloidal S QDs. At the same time, the -scanning in a closed-aperture scheme demonstrates the formation of a thermal dynamic lens.