Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 50: III-V Semiconductors II (mainly Arsenides)

HL 50.2: Talk

Wednesday, March 28, 2012, 09:45–10:00, EW 203

Generation and detection of picosecond transverse phonon pulses in high-index GaAs — •Jasmin Jäger¹, Michael Bombeck¹, Alexey Salasyuk^1,2, Alexey Scherbakov², Andrey Akimov³, Dmitri Yakovlev^1,2, and Manfred Bayer¹ — ¹Experimentelle Physik II, TU Dortmund, Germany — ²Ioffe Physical Technical Institute of the Russian Academy of Sciences, St. Petersburg, Russia — ³School of Physics and Astronomy, University Nottingham, United Kingdom

The aim of this work is the first direct observation of a picosecond coherent pulse of transverse phonons travelling a macroscopic distance through high-index GaAs. In the experiment the pump pulse of an amplified Ti:Sa-laser (800nm, 150fs duration, pulse energy up to 150µJ) excites a 100nm Al-film deposited on the back side of the GaAs slab grown along (311)-direction. The film serves as an optoelastic transducer, which expands due to the ultrafast optical heating and injects a picosecond strain pulse into the sample. The pulse travels through the 100µm tick slab and is detected at the front surface by the modulation of the linearly polarized probe pulse. The difference in the sound velocities for LA and TA acoustic phonons allows separating them in the time-resolved signal. Together with the modulation of the probe pulse intensity due to the well-known elasto-optical effect, we also detect the rotation of the probe polarization plane. The latter is due to the strain-induced linear dichroism and depends on the phonon polarization and relative orientation of the probe beam polarization plane and crystallographic directions of the slab.