Abstract: We study the coherence times of CuBr nanocrystals (quantum dots) in a borosilicate matrix under resonant excitation. Measurements are performed in two different experiments: Degenerate four-wave mixing with pulses of approximately 100 fs duration and spectral hole burning using a nanosecond excitation. Our results show a dependence of the dephasing times on the excitation intensity, and, when extrapolated to low intensity, a longer coherence time under fs than ns excitation. This result is tentatively explained as being due to spectral diffusion in the case of ns excitation. !11
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