We report the design for a high-power optical parametric chirped-pulse amplifier (OPCPA) at 3200 nm central wavelength for the MIR-HE laser at ELI-ALPS, aiming to provide 20 mJ pulse energy and sub-2.5 cycles pulse length.
High power mid-infrared (MID-IR) laser systems delivering ultrashort pulses at high repetition rates are of considerable interest for vibrational spectroscopy, label-free microscopy, ultrafast dynamics and HHG studies. To meet these requirements, we developed an optical parametric chirped-pulse amplifier (OPCPA) with a difference frequency generation (DFG) stage to provide an efficient platform to down-convert a 200 W Yb-YAG pump laser into the MID-IR range. The MID-IR pulses are tunable from 4.2-11 μm, with a maximum pulse energy around 9 μm with 2.2 μJ at 200 kHz supporting a Fourier limit of 50 fs. In addition, thermal parameters of various nonlinear crystals are reviewed for high power MID-IR OPCPAs.
Active carrier envelope phase (CEP) stabilization in the few-cycle regime is essential for most attosecond experiments, e.g. studying the coherent evolution of electronic structure and dynamics in solids or complex many body phenomena crystals. Here, we present a dual-channel optical parametric chirped-pulse amplifier (OPCPA) design providing CEP stable, sub 9 fs pulses around 800 nm center wavelength as a high-harmonic driver for attosecond experiments. Additionally, a second 1.7 - 2 μm CEP stable outlet is available. Two OPCPA designs (a) high repetition rate and (b) a high pulse-energy system will be demonstrated.
High power and high repetition rate femtosecond lasers at 1.45–2.40 μm wavelength are critical for many applications in the physical, chemical, and biological sciences, such as microchip electron accelerators and soft-X-ray coherent diffractive imaging. Previously, such systems have been realized by optical parametric amplification from Ti:Sapphire lasers at 800 nm with limited power levels. A novel optical parametric chirped-pulse amplifier (OPCPA), pumped by high-power Yb-doped solid state laser, and combined with bulk crystal white-lightgeneration seeding (WLG) is demonstrated here. The laser system features tunable and broadband operation in the 1.45–2.40 μm spectral range, requiring no complex cooling with a compact footprint. Such systems have recently become commercially available from Class 5 Photonics and allow for scalability up to millijoule pulse energies at 100 W average power.
A dual-channel, high-power laser system with gap-less tuning from 250-1300nm at 30-50 femtoseconds pulse duration is presented as the ideal tool for time-resolved photo-emission microscopy and spectroscopy experiments at repetition rates up to 4MHz.
Ultrafast dynamics experiments in physics, chemistry and biology, in condensed matter or gas phase require different types of lasers. We present various OPCPAs as a powerful toolbox to deliver femtosecond pulses from the XUV to THz spectral region. A synchronized pump-probe laser has been realized, generating visible and near-IR pump pulses (350-1300 nm) and UV pulses (250 - 350 nm) operating at 4 MHz. Furthermore, a 1.55 μm wavelength OPCPA has been demonstrated for efficient THz-generation. For XUV generation in the water window, an OPCPA is presented, delivering millijoule-level, femtosecond pulses from 1.7 - 2.2 μm with up to 100 W average power.
High power and high repetition rate femtosecond lasers are crucial tools furthering the scientific development across many fields. So far, these systems have been realized by Ti:Sapphire lasers at 800 nm, being limited in power scaling. A novel optical parametric chirped-pulse amplifier (OPCPA), pumped by high-power Yb-doped solid state lasers, and combined with bulk crystal white-light-generation seeding (WLG) allows to circumvent the limitation in average power. The presented laser system features carrier-envelope phase (CEP) stable sub 20 fs pulses centered at 800nm with millijoule pulse energies and average power of 20W while remaining on a compact footprint. Such systems have recently become commercially available from Class 5 Photonics and allow for scalability beyond millijoule pulse energies at up to 100W average power.
A review of current high power (100 W-level), femtosecond, optical parametric chirped-pulse amplifiers (OPCPA) at near IR (NIR) and short-wave IR (SWIR) wavelengths pumped by Yb-based solid-state lasers is presented. OPCPA technology together with white-light-generation (WLG) makes it possible to provide CEP-stable femtosecond broadband or tunable pulses (from 700nm to 2.1 μm), which are potentially scalable to much high power levels. An important feature of these new OPCPAs is their reliability and compact design, requiring no complex cooling systems.
XUV pulses at 26.2 nm wavelength were applied to induce graphitization of diamond through a non-thermal solid-to-solid phase transition. This process was observed within poly-crystalline diamond with a time-resolved experiment using ultrashort XUV pulses and cross correlated by ultrashort optical laser pulses. This scheme enabled for the first time the measurement of a phase transition on a timescale of ~150 fs. Excellent agreement between experiment and theoretical predictions was found, using a dedicated code that followed the non-equilibrium evolution of the irradiated diamond including all transient electronic and structural changes. These observations confirm that ultrashort XUV pulses can induce a non-thermal ultrafast solid-to-solid phase transition on a hundred femtosecond timescale.
KEYWORDS: Optical amplifiers, Crystals, Absorption, Near infrared, Nonlinear crystals, Thermal effects, High power fiber amplifiers, Finite element methods, Solids, Thermography
Laser amplifiers at high repetition rate are critical for many applications in the chemical, physical and biological sciences. A variety of laser sources from XUV to THz can be derived from Ti:Sapphire laser amplifiers at moderate to low conversion efficiencies. High repetition rate applications require NIR and IR sources based on optical parametric chirped pulse amplifier (OPCPA) to drive these sources, offsetting the conversion efficiency losses with an even higher average power beam to drive the frequency conversion processes. We use these technologies at next generation free-electron laser (FEL) facilities. The Linac Coherent Light Source (LCLS), LCLS-II upgrade, will provide sub-femtosecond and femtosecond X-ray pulses at 100 kHz, and later up to 1 MHz repetition rate. The higher repetition rate benefits pump-probe experiments for weakly scattering samples and serves a variety of experiments which require attenuation to avoid perturbation and damage of the sample by the X-ray probe. A millijoule R&D laser amplifier was developed to test experimental conditions for optical laser beam delivery at LCLS-II. The laser can be operated at two distinct wavelength ranges. At 800 nm center wavelength we use the second harmonic of an Yb:YAG amplifier system to pump an OPCPA in a BBO crystal. A second tunable version operates between 1.45-2 m center wavelength using the fundamental Yb:YAG beam to pump a KTA OPCPA with average output powers in excess of 100 W. Currently the amplifier is operated 24 hours, 7 days a week. It is based on a simple and robust design, which ensures long term stability with good output beam quality.
High power OPCPAs above 10 W at short-wave IR wavelengths (SWIR: 1.4 - 3 μm) may be limited because of thermal heat dissipation in the nonlinear crystals. In this work we provide up-to-date measurements of the absorption coefficients of the nonlinear crystals used at these wavelengths and simulations of the thermal effects on critical parameters. In particular, power scaling limits will be discussed.
Quasi-phase matching (QPM) can be used to increase the conversion efficiency of the high harmonic generation
(HHG) process. We observed QPM with an improved dual-gas foil target with a 1 kHz, 10 mJ, 30 fs laser
system. Phase tuning and enhancement were possible within a spectral range from 17 nm to 30 nm. Furthermore
analytical calculations and numerical simulations were carried out to distinguish QPM from other effects, such
as the influence of adjacent jets on each other or the laser gas interaction. The simulations were performed with
a 3 dimensional code to investigate the phase matching of the short and long trajectories individually over a
large spectral range.
Optical parametric chirped-pulse amplification (OPCPA) is the most promising method for providing compact, wavelength tunable, high power, femtosecond lasers. We have recently achieved a 112 W OPCPA with wavelength tunability around 800 nm and 30 fs pulse duration in burst mode (100 kHz in a 800 µs burst at 10 Hz). In this work, we discuss the various laser architectures and the critical parameters in achieving similar laser parameters but in continuous operation.
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