Exciton dephasing time in CuBr quantum dots

We perform degenerate four-wave mining on CuBr quantum dot samples on a femtosecond time scale. Due to inhomogeneous broadening, we observe a so called photon-echo signal. The signal dynamics measured at different pump intensities provide information on the dephasing time. We study this dephasing time at 5 K as a function of the excitation wavelength. We also determine the homogeneous absorption linewidth by spectral hole burning measurements, in the same sample, at 5 K, using a nanosecond dye laser excitation. This is an alternative indirect method to determine dephasing times and we can compare both results. We then conclude on the difficulties of measuring dephasing limes in confined systems by the latter method. (C) 1998 Elsevier Science B.V.