Coherent field sensing of nitrogen dioxide.

We introduce a portable dual-comb spectrometer operating in the visible spectral region for atmospheric monitoring of NO, a pollution gas of major importance. Dual-comb spectroscopy, combining key advantages of fast, broadband and accurate measurements, has been established in the infrared as a method for the investigation of atmospheric gases with kilometer-scale absorption path lengths. With the presented dual-comb spectrometer centered at 517 nm, we make use of the strong absorption cross section of NO in this spectral region.

Agile spectral tuning of high order harmonics by interference of two driving pulses.

In this work, the experimental realization of a tunable high photon flux extreme ultraviolet light source is presented. This is enabled by high harmonic generation of two temporally delayed driving pulses with a wavelength of 1030 nm, resulting in a tuning range of 0.8 eV at the 19 harmonic at 22.

Ultraviolet dual comb spectroscopy: a roadmap.

Dual Comb Spectroscopy proved its versatile capabilities in molecular fingerprinting in different spectral regions, but not yet in the ultraviolet (UV). Unlocking this spectral window would expand fingerprinting to the electronic energy structure of matter. This will access the prime triggers of photochemical reactions with unprecedented spectral resolution.

Ultrafast quantum control of ionization dynamics in krypton.

Ultrafast spectroscopy with attosecond resolution has enabled the real time observation of ultrafast electron dynamics in atoms, molecules and solids. These experiments employ attosecond pulses or pulse trains and explore dynamical processes in a pump-probe scheme that is selectively sensitive to electronic state of matter via photoelectron or XUV absorption spectroscopy or that includes changes of the ionic state detected via photo-ion mass spectrometry. Here, we demonstrate how the implementation of combined photo-ion and absorption spectroscopy with attosecond resolution enables tracking the complex multidimensional excitation and decay cascade of an Auger auto-ionization process of a few femtoseconds in highly excited krypton.

Thin-disk pumped optical parametric chirped pulse amplifier delivering CEP-stable multi-mJ few-cycle pulses at 6 kHz.

We present an optical parametric chirped pulse amplifier (OPCPA) delivering CEP-stable ultrashort pulses with 7 fs, high energies of more than 1.8 mJ and high average output power exceeding 10 W at a repetition rate of 6 kHz. The system is pumped by a picosecond regenerative thin-disk amplifier and exhibits an excellent long-term stability.

Coherent Raman spectro-imaging with laser frequency combs.

Advances in optical spectroscopy and microscopy have had a profound impact throughout the physical, chemical and biological sciences. One example is coherent Raman spectroscopy, a versatile technique interrogating vibrational transitions in molecules. It offers high spatial resolution and three-dimensional sectioning capabilities that make it a label-free tool for the non-destructive and chemically selective probing of complex systems.

Vacuum ultraviolet frequency combs generated by a femtosecond enhancement cavity in the visible.

We present the first (to our best knowledge) femtosecond enhancement cavity in the visible wavelength range for ultraviolet frequency comb generation. The cavity is seeded at 518 nm by a frequency-doubled Yb fiber laser and operates at a peak intensity of 1.2×10(13) W/cm(2).

Improved measurement of the hydrogen 1S-2S transition frequency.

We have measured the 1S-2S transition frequency in atomic hydrogen via two-photon spectroscopy on a 5.8 K atomic beam. We obtain f(1S-2S) = 2,466,061,413,187,035 (10)  Hz for the hyperfine centroid, in agreement with, but 3.

Power scaling of a high-repetition-rate enhancement cavity.

A passive optical resonator is used to enhance the power of a pulsed 78 MHz repetition rate Yb laser providing 200 fs pulses. We find limitations relating to the achievable time-averaged and peak power, which we distinguish by varying the duration of the input pulses. An intracavity average power of 18 kW is generated with close to Fourier-limited pulses of 10 W average power.

Implementation and characterization of a stable optical frequency distribution system.

An optical frequency distribution system has been developed that continuously delivers a stable optical frequency of 268 THz (corresponding to a wavelength of 1118 nm) to different experiments in our institute. For that purpose, a continuous wave (cw) fiber laser has been stabilized onto a frequency comb and distributed across the building by the use of a fiber network. While the light propagates through the fiber, acoustic and thermal effects counteract against the stability and accuracy of the system.