Time-resolved degenerate four-wave-mixing in layered materials: photon-echo and transient grating measurements

Hideaki Tobioka, Yasuyosi Mitsumori, F. Minami

Maxim F. Gelin, Dassia Egorova, Wolfgang Domcke

An efficient method has been developed for the calculation of third-order time- and frequency-resolved optical signals. To obtain the general four-wave mixing signal, seven auxiliary density matrices have to be propagated in time. For the special cases of two-pulse photon-echo and transient-grating signals, two or three density matrices, respectively, are required. The method is limited to weak laser fields (it is thus valid within the third-order perturbation theory) but allows for any pulse durations and automatically accounts for pulse-overlap effects. To illustrate the method, we present the explicit derivation of the three-pulse photon-echo signal. Any other third-order optical signal can be calculated in the same manner. As an example, two- and three-pulse photon-echo and transient-grating signals for a weakly damped displaced harmonic oscillator have been calculated.

南不二雄, F. Minami

H. Nickolaus, F. Henneberger

We have performed time-integrated as well as time-resolved femtosecond degenerate four-wave-mixing measurements on inhomogeneously broadened (Zn,Cd)Se/ZnSe quantum-well structures. Potential fluctuations due to alloy disorder in the ternary wells give rise to localized quasi-zero-dimensional excitons and biexcitons. For time-integrated detection, they manifest themselves by distinct (disorder-renormalized) quantum beats. Time resolving these transients reveals a free-induction-decay-like emission nature of the biexciton in contrast to the photon-echo exciton contribution. Using a five-level scheme, containing both biexcitons and antibound two-exciton states, this striking emission-type change is explained by fluctuation and correlation effects upon the biexciton binding energy. A combination of time-resolved and time-integrated four-wave mixing is thus a powerful tool to gain information about the disorder in a given kind of quantum structure.

Иванин Константин Валерьевич, Andrey V. Leontyev, Vladimir S. Lobkov +1 more

We report femtosecond photon echo and four-wave mixing measurements performed on GaAs/AlGaAs heterostructure at room temperature. In femtosecond photon echo experiment the dephasing time was obtained, found to vary between 40 and 55 fs depending on carrier density. The dependence showed a power-law behavior T 2 ∝ N -0.22 , which indicates that major phase coherence loss is due to screened Coulomb electron-electron interaction. Transient grating experiments yielded the electron diffusion coefficient value of 200 cm 2 /s and electron relaxation time equal to 3 ns.

Stephen Mark Jensen