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Vacuum chambers are frequently used in high-energy, high-peak-power laser systems to prevent deleterious nonlinear effects, which can result from propagation in air. In the vacuum sections of the Allegra laser system at ELI-Beamlines, we observed degradation of several optical elements due to laser-induced contamination (LIC). This contamination is present on surfaces with laser intensity above 30 G W / c m 2 with wavelengths of 515, 800, and 1030 nm. It can lead to undesired absorption on diffraction gratings, mirrors, and crystals and ultimately to degradation of the laser beam profile. Because the Allegra laser is intended to be a high-uptime source for users, such progressive degradation is unacceptable for operation. Here, we evaluate three methods of removing LIC from optics in vacuum. One of them, the radio-frequency-generated plasma cleaning, appears to be a suitable solution from the perspective of operating a reliable, on-demand source for users.

Stable picosecond supercontinuum generated in long crystals is an excellent means of seeding broadband, high-energy CPA systems. The generated output energy and spectrum can be almost three times as stable as the pump for a wide range of input pulse parameters. In this work, we show this is an intrinsic property for crystals longer than the filament and for a range of input energy values. We present a description of the stability mechanism in both the visible and infrared regions together with experimental data that support the theoretical explanation.

In this paper, the authors present the characterization experiments of a 20 fs vacuum ultraviolet beam from a high harmonic generation source. The beam hits a silicon sample and passes a triple reflection gold polarizer located inside an ultrahigh vacuum chamber. The polarizer’s Malus curve was obtained; the total acquisition time for each point of the curve was 30 s. This aims to be the first vacuum ultraviolet time-resolved user station dedicated to ellipsometry. The high harmonic beam is generated by a 12 mJ, 1 kHz, 20 fs, in-house-developed laser and detected by a back-illuminated charge-coupled device.In this paper, the authors present the characterization experiments of a 20 fs vacuum ultraviolet beam from a high harmonic generation source. The beam hits a silicon sample and passes a triple reflection gold polarizer located inside an ultrahigh vacuum chamber. The polarizer’s Malus curve was obtained; the total acquisition time for each point of the curve was 30 s. This aims to be the first vacuum ultraviolet time-resolved user station dedicated to ellipsometry. The high harmonic beam is generated by a 12 mJ, 1 kHz, 20 fs, in-house-developed laser and detected by a back-illuminated charge-coupled device.

We report on the status of the Allegra laser beamline currently being commissioned at the ELI-Beamlines facility. The beamline will be used to drive X-ray sources for research in material science, molecular physics, and biophysics, where a high repetition rate is essential. Designed for user operation, significant attention is given to stability, reliability, and automation of the system. A photo of the beamline is shown in Fig. 1(a).

We discuss the performance of several stages of high energy, high average power SHG and OPCPA with picosecond pulses in vacuum as part of the ALLEGRA laser at ELI-Beamlines.

We present a broadband optical parametric chirped pulse amplification (OPCPA) system delivering 4 J pulses at a repetition rate of 5 Hz. It will serve as a frontend for the 1.5 kJ

Overview of progress in construction and testing of the laser systems of ELI-Beamlines, accomplished since 2015, is presented. Good progress has been achieved in construction of all four lasers based largely on the technology of diode-pumped solid state lasers (DPSSL). The first part of the L1 laser, designed to provide 200 mJ

We report on the status of the high repetition rate, high energy, L1 laser beamline at the ELI-Beamlines facility. The beamline is based on picosecond optical parametric chirped pulse amplification (OPCPA) of pulses from a mode-locked Ti:Sapphire oscillator and has a target energy/repetition rate of 100 mJ/1 kHz with < 15fs pulse duration. The OPCPA pump lasers use thin disk technology to achieve the high energy and average power required to pump such a high energy, high repetition rate broadband amplifier. Here we report on the progress in beamline development and discuss the technical challenges involved in producing such a system and their solutions. A major focus of the laser development is reliable, robust operation and long term stability; mechanical, optical, and control system architecture design considerations to achieve our goals of long term stability are discussed.

We present an active cavity pointing stabilization system based on a novel method that tracks the cavity mode position directly on the thin disk gain medium itself. Here, the overlap of the lasing cavity with the pump, visible as a depletion within the pumped area, is most crucial to the stability of the laser. Short term stability as well as long term stability are significantly increased enabling day long operation, directly from a cold start of the laser system, without the need for thermalization and manual alignment.

We present a stable supercontinuum (SC) generated in a bulk YAG crystal, pumped by 3 ps chirped pulses at 1030 nm. The SC is generated in a loose focus geometry in a 13 cm long YAG crystal, allowing for stable and robust single-filament generation. The SC energy stability exceeds that of the pump laser by almost a factor of 3. Additionally, we show that the SC spectrum has long-term stability and that the SC is coherent and compressible by compressing the portions of SC spectra close to the corresponding Fourier limit. This makes the picosecond-pulse-driven SC a suitable stable seed for OPCPA amplifiers.

We report on the design and performance of a fiber-based, multi-channel laser amplifier seed pulse distribution system. The device is designed to condition and distribute low energy laser pulses from a mode-locked oscillator to multiple, highly synchronized, high energy amplifiers integrated into a laser beamline. Critical functions such as temporal pulse stretching well beyond 100 ps/nm, pulse picking, and fine control over the pulse delay up to 300 ps are all performed in fiber eliminating the need for bulky and expensive grating stretchers, Pockels cells, and delay lines. These functions are characterized and the system as a whole is demonstrated by seeding two high energy amplifiers in the laser beamline. The design of this system allows for complete computer control of all functions, including tuning of dispersion, and is entirely hands-free. The performance of this device and its subsystems will be relevant to those developing lasers where reliability, size, and cost are key concerns in addition to performance; this includes those developing large-scale laser systems similar to ours and also those developing table-top experiments and commercial systems.

We present a stable supercontinuum generation in a YAG crystal, driven by 3 ps pulses at 1030 nm. The supercontinuum is demonstrated to be coherent and compressible by Dazzler and prism compressor to below 15 fs.

We report on a broadband OPCPA system, pumped at 515 nm by frequency doubled Yb:YAG thin disk lasers. The system delivers 11.3 mJ pulses at a central wavelength of 800 nm with a spatial beam quality of Msup2/sup= 1.25 and25% pump-to-signal conversion efficiency. The broadband pulses were demonstrated to be compressible to 12 fs using a chirped mirror compressor.

We report on a frequency-doubled picosecond Yb:YAG thin disk regenerative amplifier, developed as a pump laser for a kilohertz repetition rate OPCPA. At a repetition rate of 1 kHz, the compressed output of the regenerative amplifier has a pulse duration of 1.2 ps and pulse energy of 90 mJ with energy stability of σ < 0.8% and M2 < 1.2. The pulses are frequency doubled in an LBO crystal yielding 42 mJ at 515 nm.

We report on the implementation of intensity-dependent filter for picosecond pulse temporal cleaning based on an effect of pulse polarization rotation during the unbalanced phase matched second harmonic generation. The pulse contrast enhancement by more than two orders of magnitude and filter transmission of ∼25% has been demonstrated at pulse intensities of

We present simple analytical solutions of coupled wave equations describing chirped pulse parametric amplification under pump depletion. The evolution of the duration and spectrum of amplified pulses in OPA pumped by Gaussian and supergaussian pulses has been investigated both numerically and analytically. Also, the dependence of the energy conversion efficiency from pump to signal was determined for a range of parameter values, and an optimum ratio of signal and pump pulse durations was evaluated.

We present a multistage 1 kHz OPCPA system, pumped by two frequency doubled thin disk regenerative amplifiers, delivering together 57 mJ at 515 nm. The OPCPA produces 8 mJ of amplified signal and is compressible to < 27 fs.