Abstract
The rapid development of extreme ultraviolet (EUV) and x-ray ultrafast coherent light sources such as free electron lasers (FELs) has triggered the extension of wave-mixing techniques to short wavelengths. This class of experiments, based on the interaction of matter with multiple light pulses through the Nth order susceptibility, holds the promise of combining intrinsic ultrafast time resolution and background-free signal detection with nanometer spatial resolution and chemical specificity. A successful approach in this direction has been the combination of the unique characteristics of the seeded FEL FERMI with dedicated four-wave-mixing (FWM) setups, which leads to the demonstration of EUV-based transient grating (TG) spectroscopy. In this perspective paper, we discuss how the TG approach can be extended toward more general FWM spectroscopies by exploring the intrinsic multiparameter nature of nonlinear processes, which derives from the ability of controlling the properties of each field independently.
Highlights
The nonlinear optical response of matter arises from the interaction of strong electromagnetic fields through the Nth order susceptibility of a material, in what is called an (N þ 1) wave mixing process
A successful approach in this direction has been the combination of the unique characteristics of the seeded free electron lasers (FELs) FERMI with dedicated four-wave-mixing (FWM) setups, which leads to the demonstration of extreme ultraviolet (EUV)-based transient grating (TG) spectroscopy
We review the current status of EUV FWM, describing the most recent achievements obtained at FERMI using mini-TIMER and TIMER, and build up on this to discuss the foreseen efforts to exploit the VIS-EUV TG setup for the exploration of multidimensional spectroscopies
Summary
The nonlinear optical response of matter arises from the interaction of strong electromagnetic fields through the Nth order susceptibility of a material, in what is called an (N þ 1) wave mixing process. Far from electronic resonances, the third order nonlinear susceptibility scales as the inverse of the frequency squared for each of the incoming beams, causing a significant decrease in the cross sections when moving from visible to EUV photon energies.[24] These limitations have been recently overcome in two dedicated setups that were developed and implemented at the FERMI FEL source[26] with the aim of performing noncollinear EUV FWM experiments based on the TG scheme: the compact EUV-optical wave mixing setup mini-TIMER and the purely EUV-FWM beamline TIMER.[11] TG experiments are a particular class of FWM where two of the incoming pulses, called the “pump,” have the same frequency and are overlapped in time (s1 1⁄4 0) on the sample at an angle to generate a transient standing wave that effectively acts as a diffraction grating for the third pulse, the “probe.” The interference pattern of the two pumps excites impulsive modes with momentum. Both setups allow the variation of the pump and probe wavelengths, which can be selectively tuned to resonances or used in more complex multicolor wave mixing processes such as coherent Raman scattering
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
