Ultrafast laser spectroscopy is a valuable tool for exploring dynamics on short time scales, but it often requires lengthy measuring times. Recently, researchers led by Hanieh Fattahi at the Max-Planck-Institute of the Science of Light developed a technique to speed up spectroscopic analysis. By using ultrashort pulses with broad spectral bandwidth, researchers can characterize samples at various frequencies simultaneously, eliminating the need for repeated measurements. Additionally, the temporal confinement of these pulses allows for the isolation of a sample’s response, which carries important spectroscopic information lasting from tens of femtoseconds to nano-seconds.
The challenge of real-time measurements in ultrafast spectroscopy arises from the extensive data recording required across the high bandwidth spectrum. These delays in data capture, processing time, and increased data volume hinder the efficient acquisition of spectroscopic data. However, researchers have successfully implemented compressed sensing, a method that strategically randomizes measurement points in time to reconstruct signals efficiently using fewer data points than required by the Nyquist criterion. By collaborating with partners in Germany and France, acoustic waves were used to randomly modulate the temporal overlap of probe pulses and femtosecond excitation pulses, allowing for real-time spectroscopic measurements.
Kilian Scheffter, a doctoral student working with Hanieh Fattahi, explains that the sparse responses of molecules to ultra-short excitation pulses can be efficiently reconstructed using compressed sensing. This technique not only accelerates time domain spectroscopy but also expands its application to various fields such as label-free imaging of fragile specimens, real-time environmental monitoring, and molecular fieldoscopy. By randomizing the temporal overlap of probe and excitation pulses, researchers have overcome the main challenge of implementing compressed sensing in ultrafast spectroscopy, enabling faster and more efficient spectroscopic analysis.
The developments in ultrafast spectroscopy not only enhance the speed and efficiency of spectroscopic analysis but also open up new possibilities for applications in various scientific and industrial settings. The ability to perform real-time measurements in spectroscopic analysis can simplify processes such as label-free imaging of fragile samples, environmental monitoring, and diagnostics of toxic gases. Dr. Hanieh Fattahi emphasizes the many advantages of accelerating time domain spectroscopy, highlighting its potential for innovative applications in different fields. The collaboration between researchers and industrial partners has led to significant advancements in ultrafast laser spectroscopy, paving the way for further developments in real-time spectroscopic analysis.
