"Two-Dimensional Fourier-Transform Spectroscopy: Shining New Light on Semiconductor Nanostructures"

Alan D. Bristow

West Virginia University

Real optoelectronic devices are strongly influenced by light-matter interactions. Therefore, understanding fundamental electronic dynamics and dephasing processes in the materials that comprise these devices can lead to improved performance or novel functionality. A mainstay of optoelectronics is the GaAs quantum well, which is an ideal test bed for exploring light-matter interactions. Ultrafast pulsed laser experiments provide a snapshot of the light-matter interactions. Furthermore, tailoring the excitation pulses allows for coherent control of the underpinning electronic states to overcome ambiguous spectral or temporal signatures often obtained in conventional spectroscopy. In this talk I showcase optical two-dimensional Fourier-transform spectroscopy, which uses precise control of a multi-pulse excitation sequence, to separate competing contributions onto a two-dimensional frequency plane. This “interaction fingerprint” characterizes different spectral broadening mechanisms, separated coherent coupling from incoherent relaxation processes, and reveals many-body interactions. The technique is applied to excitonic (electron-hole pair) interactions in GaAs quantum wells to explore the interplay of disorder and many-body correlations. I will also discuss some work on GaAs quantum dot ensembles and future directions.