Maxim Tschernajew

High-average-power 2 μm few-cycle optical parametric chirped pulse amplifier at 100 kHz repetition rate

Sources of long wavelengths few-cycle high repetition rate pulses are becoming increasingly important for a plethora of applications, e.g., in high-field physics. Here, we report on the realization of a tunable optical parametric chirped pulse amplifier at 100 kHz repetition rate. At a central wavelength of 2 μm, the system delivered 33 fs pulses and a 6 W average power corresponding to 60 μJ pulse energy with gigawatt-level peak powers. Idler absorption and its crystal heating is experimentally investigated for a BBO. Strategies for further power scaling to several tens of watts of average power are discussed.

Table-top milliwatt-class extreme ultraviolet high harmonic light source

Extreme ultraviolet (XUV) lasers are essential for the investigation of fundamental physics. Especially high repetition rate, high photon flux sources are of major interest for reducing acquisition times and improving signal to noise ratios in a plethora of applications. Here, an XUV source based on cascaded frequency conversion is presented, which delivers due to the drastic better single atom response for short wavelength drivers, an average output power of (832 +- 204) {\mu}W at 21.7 eV. This is the highest average power produced by any HHG source in this spectral range surpassing precious demonstrations by more than a factor of four. Furthermore, a narrow-band harmonic at 26.6 eV with a relative energy bandwidth of only {\Delta}E/E= 1.8 x 10E-3 has been generated, which is of high interest for high precision spectroscopy experiments.

Scalability of components for kW-level average power few-cycle lasers.

In this paper, the average power scalability of components that can be used for intense few-cycle lasers based on nonlinear compression of modern femtosecond solid-state lasers is investigated. The key components of such a setup, namely, the gas-filled waveguides, laser windows, chirped mirrors for pulse compression and low dispersion mirrors for beam collimation, focusing, and beam steering are tested under high-average-power operation using a kilowatt cw laser. We demonstrate the long-term stable transmission of kW-level average power through a hollow capillary and a Kagome-type photonic crystal fiber. In addition, we show that sapphire substrates significantly improve the average power capability of metal-coated mirrors. Ultimately, ultrabroadband dielectric mirrors show negligible heating up to 1 kW of average power. In summary, a technology for scaling of few-cycle lasers up to 1 kW of average power and beyond is presented.

High Photon Flux 70 eV HHG Source for Applications in Molecular and Solid State Physics

A 100 kHz high harmonic source with record high >1011 photons/s in single harmonics between 55-73 eV is presented. The unique capabilities are underlined by using it for coincidence experiments and measurements on magnetic samples.

Milliwatt-class high harmonic generation with an high average power short wavelength fiber laser

Table-top extreme ultraviolet (XUV) light sources with laser like properties are of interest in a vast variety of applications. To achieve such light pulses with femtosecond pulse durations, high harmonic generation (HHG) is an established technique. It delivers ultrashort pulses and a wide range of photon energies, suitable for the study of core level transitions, highly excited states, or transitions in highly-charged ions [1], as well as for experiments in solid state physics such as photoelectron spectroscopy [2]. To achieve short acquisition times as well as acceptable signal to noise ratios, a high repetition rate and high photon flux is beneficial. Therefore, average power scalable fiber-based lasers are an ideal driver [3]. Since the HHG single atom response scales with ∼λ−5.5 [4] and phase matching conditions are more beneficial for a shorter driving wavelength, a much higher overall conversion efficiency can be achieved for short wavelength drivers [5]. By using the second harmonic of an infrared laser for HHG we demonstrate the highest average power high harmonic source to date. This cascaded frequency conversion yields a record high average power of (832 + 204) μW, contained in a single harmonic line at 21.7 eV with a relative energy bandwidth of ΔΕ/E ≈ 10−2, shown in Fig. 1a) [6].

Multi-GW, 100 fs thulium-doped fiber laser system for high-harmonic generation at high repetition rates

Intense, ultrafast laser systems with an emission wavelength at around 2 μm have become popular tools for many scientific research activities such as nonlinear frequency conversion into the long-wave mid-infrared [1] as well as the soft X-ray spectral region [2], in order to address numerous subsequent applications. There is, however, a strong application-driven demand for an increase in photon-flux, i.e. repetition rate and average power, of the driving laser systems. Thulium-doped fiber lasers are an average-power scalable laser concept at around 2 μm emission wavelength. They have been demonstrated with >100 W average power and show great promise to deliver peak powers of several tens of GW [3, 4]. Another advantage is the large gain bandwidth offered by Tm-doped fused silica, spanning from 1.8–2 μm [5].

Narrowband High Harmonic Source with Multi-mW Average Power Based on Cascaded Frequency Conversion

We report on a fiber laser based XUV source generating record high average powers of up to 2.8 mW (8*1014photons/s) in a single harmonic at 21.6 eV and narrow relative energy bandwidths down to 3*10-3 at 26.6 eV.

mW Average Power Narrowband High Harmonic Sources

Efficient HHG with a frequency-doubled fiber laser yields 970 μW in a single narrowband harmonic at 21.6 eV. In argon the energy bandwidth of H11 at 26.6 eV is ΔE/E=2*10-3 due to a window- resonance.