High resolution photocurrent‐spectroscopy of a single quantum dot

Abstract

AbstractWe report on high resolution photocurrent spectroscopy of a single quantum dot. Our attention applies to the two‐level character of a single InGaAs/GaAs quantum dot, defined by the ground state exciton. With high resolution photocurrent spectroscopy we analyze the behaviour of a single quantum dot under cw‐excitation. Experiments include linewidth, powerbroadening and saturation analysis. In the limit of low optical excitation we observe a ground state line width down to 4 µeV. With increasing excitation intensities the line width shows a characteristic power broadening. This effect is a direct consequence of the saturation of the absorption in a two‐level system under conditions of high excitation intensities. Using the high resolution we are able to measure the excitonic fine structure splitting in the ground state. The results of the cw‐excitation experiments indicate as an almost perfect quantum mechanical two‐level system. These experiments are essential for coherent manipulation of single quantum dots, important for possible applications in quantum information processing. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)