Nonlinear spectrometer for collinear four-wave mixing

• Subject Area: Condensed Matter Physics
• Term: Funded in 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 517518222

We apply for a collinear nonlinear spectrometer with raster scanning functionality and a corresponding broadband coherent laser source that renders it possible to create ultrashort laser pulses in the full wavelength range between 570 nm and 930 nm. The nonlinear spectrometer will be applied to perform collinear four-wave mixing with high spatial resolution and mainly for two-dimensional Fourier transform spectroscopy whichrenders it possible to record the spectrum, inhomogeneous linewidths, homogeneous linewidths and couplings and coherences between states in a quick and efficient manner. As a modern spectroscopy tool, the nonlinear spectrometer will provide a significant contribution towards answering fundamental cutting-edge research questions, but will also provide a means to characterize materials and samples efficiently. Relevant research questions include (a) the coupling between Rydberg excitons in bulk Cuprous Oxide and the cascaded relaxation of Rydberg excitons along states with different principal quantum number. (b) the origin and the exact behavior of hypersensitive transitions in passivated Lanthanide Oxide thin films which show very strong shifts already in response to tiny changes of their surroundings and are therefore ideal candidates for quantum sensing applications. (c) the influence of nominally dark exciton states on polariton condensates. Due to broken symmetries optical transitions to such states may become very weakly allowed. The interplay between the magnitude of symmetry breaking and the state of the surrounding and also the couplings and interactions between bright and dark states are hard to address using conventional spectroscopic techniques. (d) the investigation and optimization of dephasing rates of bright exciton levels in perovskites. In some material classes, it is already known that there is a complex interplay between the spatial extension of the perovskite structure, the structure of the exciton energy levels and the dephasing rates. The influence of the surrounding on this complex interplay is a highly relevant question for applications of perovskites. (e) the question of the influence of non-Markovian phonon interactions in colloidal nanoplatelets. (f) applications of two-dimensional Fourier transform spectroscopy within the fram of questions in Chemistry. The possibility to obtain the homogeneous linewidths of exciton states and the couplings and coherences between states within short integration times and with high spatial resolution will bring fundamental new spectroscopic expertise to TU Dortmund university, which will increase the range of scientific questions that can be addressed drastically.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Nichtlineares Spektrometer für kollineares Vierwellenmischen
• Instrumentation Group: 5700 Festkörper-Laser
• Applicant Institution: Technische Universität Dortmund
• Leader: Professor Dr. Marc Alexander Aßmann