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HL: Fachverband Halbleiterphysik

HL 85: Poster Session II

HL 85.26: Poster

Donnerstag, 17. März 2011, 18:00–21:00, P4

Pump-Probe Spectroscopy on Superlattices: Experiment and Simulation — •Andre Bojahr, Marc Herzog, Lena Maerten und Matias Bargheer — Institut für Physik und Astronomie, Universität Potsdam, Potsdam, Germany

We present an experimental setup for highly-sensitive pump-probe measurements using a mode-locked Ti:Sa oscillator at 80 MHz in the weak excitation regime (20 µ J/cm²). To reach a sensitivity on the order of Δ R /R₀ = 10⁻⁹, we rapidly scan the delay line. This setup enables us to conduct high-precision optical experiments with a time-resolution of about 100 fs. In particular, we show transient reflectivity measurements on weakly excited oxide superlattices which exhibit modulations due to the generation of coherent acoustic phonons resulting in standing and propagating strain waves. The results are compared to strong-excitation experiments with kHz amplifier systems in which the observed reflectivity oscillations are phase-shifted. In order to gain understanding, we propose a model that allows the calculation of the transient reflectivity from the modulation of optical properties by the time-dependent strain field within the sample.