CPM Seminar

Optical Two-Dimensional Coherent Spectroscopy of Epitaxially Grown Semiconductor Quantum Dots

Steve Cundiff

JILA, NIST and University of Colorado

Optical two-dimensional coherent spectroscopy is an enhancement of the method of photon echoes. A photon echo measurement has the ability to measure the homogeneous dephasing rate in an inhomogeneously broadened ensemble. Two-dimensional coherent spectroscopy can not only do the same, but it can also determine how the dephasing rate, and other properties, vary within the inhomogeneous distribution. This ability is particularly power in systems, such as quantum dots, where the inhomogeneous distribution is due to size dispersion, thus two-dimensional coherent spectroscopy can make size-resolved measurements without the need to isolate individual quantum dots. I will first show an example of this in “natural quantum dots” that form in thin quantum wells due to width fluctuations. I will then show that two-dimensional coherent spectroscopy can monitor the transfer of excitons between the two-dimensional quantum well like states and the quantum dots. I will then shift to InAs self-organized quantum dots where we are able to measure the biexciton binding energy as a function of dot size, observed additional signals due to fifth-order processes and measure the fine-structure splitting.