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HL: Halbleiterphysik

HL 4: Ultrakurzzeitph
änomene

HL 4.5: Vortrag

Montag, 8. März 2004, 11:15–11:30, H13

Coherent switching of polariton modes and their quantum beats in four-wave mixing and real-time resolved pulse-transmission experiments on ZnSe SQWs — •I. Kudyk, T. Voss, H. G. Breunig, I. Rückmann, and J. Gutowski — Institute of Solid-State Physics, University of Bremen, POB 330440, D-28334 Bremen, Germany

For layer thicknesses above 20 nm the optical properties of ZnSe nanostructures are usually dominated by the existence of different polariton modes and their interactions.

Optical coherent control of these polariton modes is investigated by use of a pair of 100 fs long phase-locked pulses in both pulse-transmission experiments with real-time resolution and four-wave-mixing (FWM) experiments. It is shown that for low excitation densities the contributions of the different resonances can be selectively enhanced or diminished. When continuously changing the inter-pulse delay time a succession of constructive and destructive interference is observed separately for each resonance. The coherent control of polariton modes also allows for a directed manipulation of the beat structures on the real-time transients as well as in the FWM signals.

Furthermore, the dephasing time of the polariton modes is analyzed in spectrally resolved, two-pulse degenerate FWM experiments and studied as a function of the excitation density and temperature. By additional measurements of the polarization states of the different spectral components the relative phase of the polariton modes is investigated.