Transient exciton optical double resonance in quantum nanostructures

A study is made of the absorption of two femtosecond probe pulses spaced by a delay time τd and of frequency Ω resonant to a transition between the ground and excitonic states in structures with quantum wells, quantum wires, or nanocrystallites. Both homogeneous and inhomogeneous exciton level broadening originating from interface roughness or dispersion in crystallite size were taken into account. It is shown that intense light of frequency ω close to resonance with a transition between two exciton levels of the same or different series can be used to control the enhancement or weakening of absorption of the second (Omega) light pulse, which oscillates with a period τd, due to the dynamic polarization of the medium induced by the first of the Ω light pulses. 22 refs., 2 figs