Fifth-order nonlinear optical response of excitonic states in an InAs quantum dot ensemble measured with two-dimensional spectroscopy

Exciton, trion, and biexciton dephasing rates are measured for an ensemble of InAs quantum dots using two-dimensional Fourier-transform spectroscopy. The two-dimensional spectra reveal that the dephasing rate of each excitonic state is similar for all dots in the ensemble and the rates are independent of excitation density. An additional spectral feature (too weak to be observed in the time-integrated four-wave mixing signal) appears at high excitation density and is attributed to the ${\ensuremath{\chi}}^{(5)}$ biexcitonic nonlinear response.