Size dependence saturation and absorption of PbS quantum dots

Abstract The saturation intensity for lead sulfide quantum dots in a titanium dioxide-glycerol matrix ( PbS / TiO 2 -glycerol) on a glass substrate has been studied as a function of quantum cluster concentration and cluster size. The saturation intensity in these materials is strongly dependent on the size of the semiconductor nanocrystals, their concentration, or the sample thickness. The samples are reflective at a certain range of the incoming intensity of the optical field and become transparent over a threshold intensity beyond which the output and input intensities are linearly related. The system studied involves very dilute distribution of PbS QD of dimension∼10 nm embedded in a matrix of TiO 2 -glycerol. Since the distribution is relatively constant in each deposited layer, the total number of QDs in a given area is proportional to the thickness. We found that the threshold of power separating absorption-bleaching, P th is linearly related to the thickness, with values of P th ∼few mW/cm 2 , more than 2–3 orders of magnitude below that of QDs with dimension∼1 μm, representing a typical solid.