Femtosecond spectrally resolved nonlinear spectroscopy: Study of Si quantum dots

We report on the use of femtosecond spectrally resolved two colour three-pulse nonlinear spectroscopy to study the carrier relaxation in Si quantum dots. The third-order polarization for a coupled two-level system is applied for theoretical simulations. The optical phonon-assisted transition leads to a fast decay (20 fs) of hot carriers.