Regensburg 2010 – wissenschaftliches Programm
HL 60.34: Poster
Donnerstag, 25. März 2010, 18:00–20:00, Poster D1
Ultrafast relaxation dynamics of coherent optical phonons in α-quartz — •Konrad von Volkmann1, Tobias Kampfrath2, Marcel Krenz1, Alexander Grujic3, Christian Frischkorn1, and Martin Wolf1,4 — 1Freie Universität Berlin, FB Physik, Arnimallee 14, 13353 Berlin, Germany — 2FOM Institute AMOLF, Science Park 113, 1098 XG Amsterdam, The Netherlands — 3Femtolasers GmbH, Fernkorngasse 10, 1100 Vienna, Austria — 4Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany
Femtosecond laser excitation of α-quartz causes oscillation of the transmitted intensity and polarization of probe light. This is due to coherent phonons modulating the real and imaginary part of the refractive index α-quartz ñquartz= n +i k. Optical phonon modes are found at 3.9, 6.3, 10.5, 12.2, and 13.9 THz. The observed amplitudes significantly depend on the probe method, either transient transmission or ellipsometry. In the case of transient transmission the signal is due to a transient lens. This effect will be discussed together with thickness and fluence dependent measurements.
We present fluence and temperature dependent data for both probe methods. These measurements show a pump-fluence independent lifetime indicating that the decay mechanism of the lattice vibrations is phonon-phonon scattering. The temperature dependence of the phonons confirms this finding and enables a detailed discussion of the relaxation mechanism of the involved coherent phonons, the anharmonic three-phonon-decay.