Researchers (including myself) always love to claim the device application potential of transition-metal dichalcogenides as the main motivator for the impact of our work. And as a matter of fact on a small scale many device applications from solar energy to lasers and even quantum information applications have been realized with this group of materials. However, the question of the scalability of these devices remains and often "magical samples" or "magical spots" are used to justify greater application claims.

Using multi-dimensional coherent imaging spectroscopy (MDCIS), we were able to study how key material properties for these device applications - ranging from temporal and spatial coherence of the excitons to coherent and incoherent coupling between them behave in the presence of strain. Spoiler alert: Some of these properties are much more robust than initially expected!

This work has been published as a featured article in the Journal of Chemical Physics.

Two-dimensional transition metal dichalcogenides (TMDs) are the most prominent group of optically active van-der-Waals materials and show promising properties such as the potential for high carrier mobility, atomic thickness, and ultrafast charge transfer. The implications of fast charge and energy transfer for optoelectronic, energy-, and light-harvesting applications has made this group of materials one of the most well-studied ones over the past years. However, previous work employed techniques not uniquely suited to study the processes in these materials, especially with respect to the temporal resolution and spectral disentanglement, yielding only insufficient information about the physics of the system.

We employ a technique called multi-dimensional coherent spectroscopy (MDCS) to study the coherent and incoherent dynamics in a MoSe₂/WSe₂ heterostructure. Using this technique, we are able to infer information about the dominance of charge transfer on a sub-picosecond time-scale in these samples and show the first experimental evidence of coherent coupling, valuable for quantum information applications, in these highly tunable materials.

This work has been published in Physical Review B.

While working at MONSTR Sense Technologies over the summer of 2020, I have developed a novel lock-in detector for nonlinear imaging that speeds up many useful, and commercialized techniques such as Stimulated Raman Scattering (SRS), with applications ranging from chemical and biological sensing to pathology in hospitals. You can find the work published in Optics Letter here.

I am excited to be working on combining laser-scanning based imaging with our advanced spectroscopic techniques into a multimodal imaging spectrometer, or, as I like to refer to it, a universal microscope. We do this with a Partnership for Innovation - Technology Transfer (PFI-TT) grant from the National Science Foundation, in close cooperation with MONSTR Sense Technologies. Stay tuned for exciting results!