The last decade has seen a breathless development of nonlinear coherent spectroscopies, and in particular four wave mixing (FWM) techniques, to investigate structural dynamics, long range interactions, charge transfer processes, or intraprotein signalling in macromolecules. In parallel, several groups have been implementing femtosecond pulse shapers to achieve full control over amplitude and phase of ultrashort pulses. These enhanced capabilities have been proved to be able to enhance specific nonlinear signals or to suppress undesired background contributions.
In our group we are developing novel approachs to investigate molecular phenomena where the insightfulness of 4WM experiments is boosted by the exceptional flexibility of pulse-shaped beams. At this aim, we recently implemented a 4WM setup in the NIR range, based on a 2D liquid crystal spatial light modulator. It allows for automated 2D pulse shaping of several fully phase coherent fields. This gives the unique capability to have a fully independent control on wave vectors, pulse delays, and phases, as well as the spectral content of each field. This approach can generate waveforms of high complexity, such as multiple pulses or chirped pulses, with a superior flexibility, even compared with conventional 4WM setups. Preliminary results on different model systems in the NIR have shown the unique capability of this approach in suppressing undesired signals and background noise providing an outstanding capability to monitor weak signals and subtle variations.
Funding: Support for Frontier Research Program (ERC). LUMS participates in the National Center of Competence in Research (NCCR) program MUST.
For further Information please contact Prof. Andrea Cannizzo.