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 differ ent pump intensities provide information on the dephasing time. We stu dy this dephasing time at 5 K as a function of the excitation waveleng th. We also determine the homogeneous absorption linewidth by spectral hole burning measurements, in the same sample, at 5 K, using a nanose cond dye laser excitation. This is an alternative indirect method to d etermine dephasing times and we can compare both results. We then conc lude on the difficulties of measuring dephasing limes in confined syst ems by the latter method. (C) 1998 Elsevier Science B.V.