Dresden 2017 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 6: Ultrafast Phenoma I

HL 6.1: Invited Talk

Monday, March 20, 2017, 09:30–10:00, POT 51

Optical Coherent Multidimensional Spectroscopy of Semiconductor Nanostructures — •Steven Cundiff — University of Michigan, Ann Arbor, Michigan, USA

Optical coherent multidimensional spectroscopy excels at removing the effects of inhomogeneity and revealing the details of coupling for resonant excitations. In semiconductors, the excitations are typically excitons. In nanostructures, inhomogeneity arises due to size and alloy fluctuations, while coupling can arise due to many-body interactions.

In quantum wells, coherent two-dimensional spectroscopy reveals the essential role of many-body interactions, both in terms of the nonlinear response of the exciton resonance and coupling between peaks. Disorder arises because of fluctuations in the well width, and 2D spectroscopy can monitor the migration of excitons among localization sites.

For very thin quantum wells, strongly localized, quantum-dot like states, are present. Using high spatial resolution, it is possible to isolate these states and observe many-body coupling that occurs due to carriers present in the quantum-well states.

Self-organized quantum dots display strong inhomogeneous broadening, which usually prevents the observation of coherent effects, such as Rabi oscillations, in an ensemble measurement. However, 2D spectroscopy allows an individual frequency group to be isolated, which in turn means that clear Rabi flopping can be observed. Furthermore, coherent control of the biexcitonic state is possible due to the broad bandwidth of the excitation pulses.