Abstract:
The concept of multidimensional coherent spectroscopy originated in NMR where it enabled the determination of molecular structure. The key concept is to correlate what happens during multiple time periods between pulses by taking a multidimensional Fourier transform. The presence of a correlation, which is manifest as an off-diagonal peak in the resulting multidimensional spectrum, indicates that the corresponding resonances are coupled. Migrating multidimensional Fourier transform spectroscopy to the optical regime is difficult because phases are critical. I will give an introduction to optical two-dimensional coherent spectroscopy, using an atomic vapor as a simple test system. I will then present our use of it to study optical resonances due to excitons in semiconductor nanostructures including transition metal dichalcogenides, where it is useful to incorporate laser-scanning microscopy.