Picosecond x-ray studies of coherent folded acoustic phonons in a multiple quantum well.
Coherent folded acoustic phonons in a multilayered GaSb/InAs epitaxial heterostructure were generated by femtosecond laser pulses and studied by means of ultrafast x-ray diffraction. Coherent phonons excited simultaneously in the fundamental acoustic branch and the first back-folded branch were detected. This represents the first clear evidence for phonon branch folding based directly on the atomic motion to which x-ray diffraction is sensitive. From a comparison of the measured phonon-modulated x-ray reflectivity with simulations, evidence was found for a reduction of the laser penetration depth. This reduction can be explained by the self-modulation of the refractive index due to photogenerated free carriers.
Sondhauss
P
P
Department of Physics, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden. peter.sondhauss@fysik.lth.se
Larsson
J
J
Harbst
M
M
Naylor
G A
GA
Plech
A
A
Scheidt
K
K
Synnergren
O
O
Wulff
M
M
Wark
J S
JS