Permanent Spectral Hole-Burning In Semiconductor Quantum Dots

Permanent spectral hole-burning under prolonged laser illumination was found in an ensemble of CdS quantum dots of a size less than the exciton Bohr radius embedded in a polymer film. The effect is attributed to a two-stage process stimulated by resonant optical excitation. At the first stage selective photoionization of the crystallites gives rise to a broadening of the relevant components in the integral absorption spectrum due to the local electric field effect. At the second stage a continuous photolytic process occurs providing an irreversible destruction of the crystallites and a characteristic dip in the absorption spectrum. In addition to various other techniques the observed phenomenon is an effective complementary tool for the analysis of quantum dot ensembles with an inhomogeneously broadened spectrum. (C) 1996 American Institute of Physics.