Jens Biegert

Formation of very-low-energy states crossing the ionization threshold of argon atoms in strong mid-infrared fields

Atomic ionization by intense mid-infrared (mid-IR) pulses produces low electron energy features that the strong-field approximation, which is expected to be valid in the tunneling ionization regime characterized by small Keldysh parameters (

Amplification of solid high harmonics in semiconductor nanostructures (Conference Presentation)

gamma ll 1

Origins of Very-Low and Zero-Energy Electron Structures in Strong-Field Ionization with Intense Mid-IR Pulses

), cannot describe. These features include the low-energy structure (LES), the very-low-energy structure (VLES), and the more recently found zero-energy structure (ZES). They result from the interplay between the laser electric field and the atomic Coulomb field which controls the low-energy spectrum also for small

High-energy, high-repetition rate, few-cycle and CEP-stable mid-IR OPCPA

gamma

A Mid-IR, High Repetition Rate, Few-Cycle Laser Source for High-Field Physics Experiments

. In the present joint experimental and theoretical study we investigate the vectorial momentum spectrum at very low energies. Using a reaction microscope optimized for the detection of very low energy electrons, we have performed a thorough study of the three-dimensional momentum spectrum well below 1 eV. Our measurements are complemented by quantum and classical simulations, which allow for an interpretation of the LES, VLES and of the newly identified ZES in terms of two-dimensional Coulomb focusing and recapture into Rydberg states, respectively.

260-mJ Ho:YLF pump for a 7-µm OPCPA

Nanoscale amplification of non-linear processes in solid-state devices opens novel applications in nano-electronics, nano-medicine or high energy conversion for example. Coupling few nano-joules laser energy at a nanometer scale for strong field physics is demonstrated. We report enhancement of high harmonic generation in nano-structured semiconductors using nanoscale amplification of a mid-infrared laser in the sample rather than using large laser amplifier systems. Field amplification is achieved through light confinement in nano-structured semiconductor 3D waveguides. The high harmonic nano-converter consists of an array of zinc-oxide nanocones. They exhibit a large amplification volume, 6 orders of magnitude larger than previously reported [1] and avoid melting observed in metallic plasmonic structures. The amplification of high harmonics is observed by coupling only 5-10 nano-joules of a 3.2 µm high repetition-rate OPCPA laser at the entrance of each nanocone. Harmonic amplification (factor 30) depends on the laser energy input, wavelength and nanocone geometry [2]. nn[1] Vampa et al., Nat. Phys. 13, 659–662 (2017). n[2] Franz et al., arXiv:1709.09153 [physics.optics] (2017)

Single-cycle, high-power, mid-IR optical parametric chirped amplifier

Intense long wavelength (λ ≥ 2 μm) laser pulses enable experiments in the tunneling ionization regime (γ 1) and reveal surprising low electron energy features, which can not be described with the strong-field approximation (SFA). These features, universal for all target species, include the low-energy structure (LES), the very-low-energy structure (VLES) and the zero-energy structure (ZES). Using full 3D electron-ion coincidence detection in combination with our ultrafast 160 kHz mid-IR source, we reveal the entire 3D momentum spectrum well below 1 eV. Quantum and classical simulations allow for an interpretation of the LES, VLES and of the newly identified ZES.

Soliton-effect self-compressed single-cycle 9.6-W mid-IR pulses from a 21-W OPCPA at 3.25 {\mu}m and 160 kHz

An OPCPA delivering optical pulses with 20 μJ energy at 160 kHz repetition rate at 3.1 μm central wavelength is reported. The pulse duration was measured to be 6 cycles and a CEP stability of 250 mrad over 10 minutes has been measured.

Single-cycle, 9.6-W, mid-IR pulses via soliton self-compression from a 21-W OPCPA at 3.25 μm and 160 kHz

We report on a high average power, few-cycle laser system operating in the mid-IR. The system delivers 20 microJoule energy pulses with ~67 fs duration at 160 kHz repetition rate with sub-250 mrad carrier-envelope-phase stability.