Regensburg 2013 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 90: Poster Session: Quantum information systems; Optical properties; Ultrafast phenomena
HL 90.18: Poster
Donnerstag, 14. März 2013, 16:00–20:00, Poster A
Generating squeezed phonons by repeated ultrafast excitations of a quantum dot — •Daniel Wigger1, Doris E. Reiter1, Vollrath Martin Axt2, and Tilmann Kuhn1 — 1Institut für Festkörpertheorie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster — 2Theoretische Physik III, Universität Bayreuth, 95440 Bayreuth
We study theoretically squeezing properties of phonon wave-packets generated by ultrafast optical excitations of a semiconductor quantum dot (QD). We model the QD in the strong confinement limit as an electronic two-level system coupled to longitudinal acoustic (LA) phonons via deformation potential. An ultrashort laser pulse creates an exciton in the QD, which leads to a shift of the equilibrium position of the lattice ions. Thus, a static lattice deformation in the QD area builds up forming a polaron state. Due to the rapid contraction of the lattice an additional strain pulse leaves the QD. Manipulating the exciton with a second laser pulse another phonon wave packet is emitted. Depending on the time delay and relative phase between the two laser pulses the fluctuation properties of the second wave packet can fall below their vacuum limit, i.e., squeezing may occur. In contrast to optical phonons, which are confined to the QD, here the squeezing feature is imprinted to the second traveling wave packet and leaves the QD.