Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 16: Quantum dots and wires: Optical properties I
HL 16.7: Vortrag
Montag, 25. Februar 2008, 15:45–16:00, ER 164
Nonlinear Optical Microscopy of a Single Self-assembled InGaAs Quantum Dot — •Claudia Ruppert1, Markus Wesseli1, Emily C. Clark2, Jonathan J. Finley2, and Markus Betz1 — 1Physik-Department E11, TU München — 2Walter Schottky Institut and Physik-Department E24, TU München
Semiconductor quantum dots (QDs) exhibit exciting prospects for solid state qubits. Here we present the first ultrafast all-optical scheme for manipulation and read-out of a single QD and, thereby, pave the way towards a variety of such quantum coherent studies [1].
A single InGaAs/GaAs QD is isolated by an aluminum shadow mask of 450 nm diameter. Optical excitation and read-out is achieved in a nondegenerate pump-probe scheme. Carriers are generated in the wetting layer beneath the QD with a 100 fs pump pulse and captured into the QD. The excitation induced transmission changes are analyzed over a broad range of probe wavelengths and various delay times. In particular, we identify signatures of the single exciton transition at EX = 1.374 eV and transitions of several multi-exciton complexes. These bleaching signals are in the order of Δ T/T ∼ 10−5 and reveal a picosecond dynamics likely related to intra-QD carrier relaxation.
In the next step, we will analyze QDs with excitonic transitions around 1.3 eV which are characterized by a larger confinement potential and better optical quality. To this end, we have developed a novel femtosecond Ti:Sapphire oscillator that, remarkably, provides ∼30 fs pulses tunable to wavelengths as long as 970 nm.
[1] M. Wesseli et al., Appl. Phys. Lett. 88, 203110 (2006).