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Project B.1.1

Fig. B.1.3: Schematic top-view of the world’s first UHV attosecond apparatus: the AS-3 beamline at MPQ. The back plate of the preparation chamber is rotatable so that the manipulator with the sample can be moved to different ports for target preparation and characterisation before the sample is inserted into the measurement

Multidimensional frequency-comb spectroscopy

This project aims at extending the capabilities of spectroscopy with laser frequency comb sources. Dual-comb spectroscopy, which exploits time-domain interferences between two frequency combs for the rapid and sensitive acquisition of highly multiplexed absorption spectra of molecules, has been successfully demonstrated during the first funding period. Compared to conventional Michelson based Fourier transform spectroscopy, recording times could be shortened from seconds to microseconds. Non-linear multi-comb spectroscopic imaging and XUV dual-comb spectroscopy are now foreseen to widen the range of applications in molecular science.

A first aspect of the project addresses advanced nonlinear spectroscopy and imaging of atoms and molecules. Since laser frequency combs involve intense ultrashort laser pulses nonlinear interactions can be harnessed, such as stimulated Raman transitions or selective excitation via waveform shaping.

Thanks to novel laser frequency comb developments in the mid-infrared and ultraviolet region, mapping of coherent transient signals emitted by a material following its excitation by a sequence of two or more femtosecond pulses will be explored and might even extend the tremendous capabilities of multi-dimensional NMR to the study of electronic and vibrational couplings. Second, dual-comb spectroscopy will be used as a new approach for the characterisation of ultrashort XUV pulse fields.

This is especially relevant for high-harmonic generation (HHG) at very high repetition frequencies (100 MHz) which may allow for the revolutionary transfer of frequency combs to the vacuum-ultraviolet range. Once the coherence of the combs developed in Project A.1.2 (Attosecond spectroscopy of electron correlation and wavepacket dynamics in atoms) will be checked our technique will be applied to spectroscopic studies of atoms and small molecules in the still unexplored XUV region.

Project Leader