Changing debris orbits using High Power Pulsed Laser Interaction (HP PLI) finds interest in the Low-Earth Orbit (LEO) due to space debris congestion. Laser facilities allowing both high energy and repetition rate of a short pulsed irradiation become available as provided by the high power HiLASE beamline facility (Prague, CZ) with BIVOJ (100J, 10ns, 10Hz, 1030nm). In order to illustrate such an application, originally Crookes radiometer concept was adapted to quantify the efficiency of repeated laser shots in increasing rotating speed according to laser matter interaction. Various materials, from model to space applicative materials, allowed to estimate the material response with various irradiation characteristics (single shots vs. repeated shots). Matter behaviors (ablation, cratering, spallation, perforation) bracketed the laser conditions suitable in the perspective of laser propulsion with limited creation of extra debris or irradiated structures damages. Next is to strengthen the robustness of the simulation/experiment dialog to use simulation as a predesign tool for laser space propulsion.
We report on the successful commissioning of DiPOLE-100Hz, a DPSSL amplifying nanosecond pulses to 10 J energy at 100 Hz repetition rate. As part of initial commissioning experiments, the system was configured to amplify 15 ns pulses at 100 Hz pulse rate to an energy of 7 J. The system was operated at this level for four hours (corresponding to 1.44·106 shots) with an energy stability of 1% rms. Subsequently, the laser demonstrated amplification of 15 ns pulses to the full specification of 10 J, 100 Hz, corresponding to 1 kW average power, with an optical-to-optical efficiency of 25.4% and long-term energy stability of less than 1% rms measured over one hour. To the best of our knowledge, this is the first time long-term, reliable operation of a kW-class high energy nanosecond pulsed DPSSL at 100 Hz has been demonstrated.
Laser beam distribution system (LBDS) is an important component at any high-power laser facility. Being a system of mirrors, lenses, and windows, the LBDS can significantly contribute to the laser beam quality degradation at target location. Phase correcting methods are among the few instruments allowing efficient control over the laser spot quality at the application site. We present a simpler solution utilizing only a PSF camera at every site. The PSF optimization is a sensorless modal correction algorithm, where each Legendre polynomial is scanned by the deformable mirror to find the best shape that maximize the PSF sharpness metric.
Laser amplifiers producing high energy (multi-J) nanosecond pulses at high repetition rate (multi-Hz) are required for a wide range of commercial and scientific applications. The DiPOLE concept, developed at the STFC Central Laser Facility (UK), consists in scalable, high-energy DPSSL amplifiers based on cryogenically-cooled, multi-slab ceramic Yb:YAG. In this work we discuss the most recent developments aimed at scaling the pulse repetition of new generation DiPOLE lasers from 10 Hz to 100 Hz. We present the design and current status of a 10 J, 100 Hz DiPOLE laser. We will discuss thermal management approaches adopted for this system.
Crytur is a company with long tradition of growing and processing crystals for technical applications, with history reaching back to 1943. Recently we have developed Crystal Improved Growth (CRIG) method for production of large core-free single crystals of YAG. The diameter currently achieved is 140 mm (in case of undoped crystal), and the crystal weight is up to 10 kg. The method was used to grow un-doped YAG crystals, YAG:Ce crystals for large scintillating screens, and Yb:YAG and Nd:YAG for high power solid-state laser systems.
Large laser slabs were manufactured from Yb:YAG doped crystals for Diode-Pumped Solid State Laser (DPSSL) system Amos, which operates within Extreme Light Infrastructure in the Czech republic (ELI Beamlines). The dimension of the largest Yb:YAG laser slab produced is 120×120×8 mm, there is no visible stress under crossed polarizers and the wavefront distortion in the clear aperture region is smaller than λ/10 (λ=633 nm) in its Peak-to-Valley value. The edges of the slab are from diffusively bonded Cr:YAG cladding in order to suppress ASE (Amplified Spontaneous Emission).
In 2018 the performance of three sets of laser slabs (ø55x5 mm) with differently realized ASE suppression was characterized at cryogenic temperatures at HiLASE Centre in terms of small signal gain measurements as well as amplification test under 30 J pumping at 1 Hz and 10 Hz repetition rates. We provide data that show that the crystal slabs have comparable properties to the ceramic slabs (produced by Konoshima company, Japan) currently in use at HiLASE.
The Photo-controlled deformable mirror (PCDM) presents an interesting alternative to the conventional deformable mirror technologies as it addresses their two major bottlenecks. It offers enormous spatial resolution while keeping its complexity low due to its elegant control of the deformable surface by light projection. The PCDM prototype was a membrane type deformable mirror driven by a modified commercial mini-projector. Unique properties of PCDM allowed experimental study of actuator array disposition influence on the wavefront shaping performance of the deformable mirror. While keeping all other aspects and parameters of the experiment constant, the four actuator-array configurations were compared and resulting wavefront shaping performance assessed.
Moreover, the Photo-controlled deformable mirror was numerically modelled and the experimental results were reproduced with high degree of fidelity. By using the numerical model of PCDM, a novel method to control high spatial resolution wavefront corrector was studied with promising results.
The HiLASE “Bivoj” laser system developed at CLF Rutherford Appleton Laboratory in collaboration with HiLASE team as DiPOLE100 was relocated to Dolni Brezany near Prague, Czechia at the end of 2015 and fully re-commissioned at the end of 2016. In 2016, the system demonstrated average output power of 1kW generating pulses of 105 J at 10 Hz repetition rate for the first time in the world. Since then the system has been subjected to several testing campaigns in order to determine some of its key characteristics. Beam quality, wavefront quality, pointing stability, energy stability and experience with long term operation of 1 kW laser are presented. In addition, depolarization effects have been detected inside the main amplifier. Details on these results along with numerical simulations are presented.
We report on the successful demonstration of the world’s first kW average power, 100 Joule-class, high-energy, nanosecond pulsed diode-pumped solid-state laser (DPSSL), DiPOLE100. Results from the first long-term test for amplification will be presented; the system was operated for 1 hour with 10 ns duration pulses at 10 Hz pulse repetition rate and an average output energy of 105 J and RMS energy stability of approximately 1%. The laser system is based on scalable cryogenic gas-cooled multi-slab ceramic Yb:YAG amplifier technology. The DiPOLE100 system comprises three major sub-systems, a spatially and temporally shaped front end, a 10 J cryo-amplifier and a 100 J cryo-amplifier. The 10 J cryo-amplifier contain four Yb:YAG ceramic gain media slabs, which are diode pumped from both sides, while a multi-pass architecture configured for seven passes enables 10 J of energy to be extracted at 10 Hz. This seeds the 100 J cryo-amplifier, which contains six Yb:YAG ceramic gain media slabs with the multi-pass configured for four passes. Our future development plans for this architecture will be introduced including closed-loop pulse shaping, increased energy, higher repetition rates and picosecond operation. This laser architecture unlocks the potential for practical applications including new sources for industrial materials processing and high intensity laser matter studies as envisioned for ELI [1], HiLASE [2], and the European XFEL [3]. Alternatively, it can be used as a pump source for higher repetition rate PW-class amplifiers, which can themselves generate high-brightness secondary radiation and ion sources leading to new remote imaging and medical applications.
We investigated wavefront aberrations in a cryogenically cooled Yb:YAG slab with a wavefront sensor using
a probe beam technique under non-lasing condition. To analyze the pump-induced phase aberrations created in the
crystal, the measured wavefronts were fitted with orthonormal Zernike polynomials. The Yb:YAG crystal of 2 mm
thickness, 10 mm diameter, and 3 at.% doping concentration was mounted in a copper holder in a closed-loop pulse tube
cryostat with cooling capacity of 12 W at 100 K. The gain medium was single-end pumped by a fiber-coupled laser
diode at pumping intensity of ~6.5 kW/cm2 with a maximum repetition rate of 100 Hz, pulse duration of 1 ms, and pump
spot diameter of 2.5 mm. The time resolved measurement revealed that defocus, which was the main wavefront
aberration, represents not only a thermal lensing effect but also an electronic lensing effect. The thermally induced
defocus is more dominant at high repetition rate than the electronically induced defocus.
We also measured wavefront aberrations of amplified beams in a cryogenically cooled Yb:YAG slab. A room
temperature operated thin-disk regenerative amplifier was used as a seed laser. The seed beam was amplified in the
cryogenically cooled crystal at 160 K in a double pass configuration. The wavefront measurement was conducted at
semi-saturated conditions, at three different repetition rates: 10 Hz, 20 Hz and 40 Hz, and at five different pump
intensities in the range between 6.5 kW/cm2 and 14.8 kW/cm2. Under lasing condition, only defocus aberration were
induced. Due to opposite signs of the defocus aberration of the seed beam and pumped induced in the Yb:YAG crystal,
wavefront of the amplified beam had smaller PtV (Peak to Valley) and RMS values than the seed beam.
We present an overview of the cryo-amplifier concept and design utilized in the DiPOLE100 laser system built for use at the HiLASE Center, which has been successfully tested operating at an average power of 1kW. Following this we describe the alterations made to the design in the second generation system being constructed for high energy density (HED) experiments in the HED beamline at the European XFEL. These changes are predominantly geometric in nature, however also include improved mount design and improved control over the temporal shape of the output pulse. Finally, we comment on future plans for development of the DiPOLE laser amplifier architecture.
In this paper we present details of the commissioning of DiPOLE100, a kW-class nanosecond pulsed diode pumped solid
state laser (DPSSL), at the HiLASE Centre at Dolní Břežany in the Czech Republic. The laser system, built at the
Central Laser Facility (CLF), was dismantled, packaged, shipped and reassembled at HiLASE over a 12 month period by
a collaborative team from the CLF and HiLASE. First operation of the laser at the end of 2016 demonstrated
amplification of 10 ns pulses at 10 Hz pulse repetition rate to an energy of 105 J at 1029.5 nm, representing the world’s
first kW average power, high-energy, nanosecond pulsed DPSSL. To date DiPOLE100 has been operated for over
2.5 hours at energies in excess of 100 J at 10 Hz, corresponding to nearly 105 shots, and has demonstrated long term
energy stability of less than 1% RMS for continuous operation over 1 hour. This confirms the power scalability of multislab
cryogenic gas-cooled amplifier technology and demonstrates its potential as a laser driver for next generation
scientific, industrial, and medical applications.
In this paper, we review the development, at the STFC’s Central Laser Facility (CLF), of high energy, high repetition rate diode-pumped solid-state laser (DPSSL) systems based on cryogenically-cooled multi-slab ceramic Yb:YAG. Up to date, two systems have been completed, namely the DiPOLE prototype and the DiPOLE100 system. The DiPOLE prototype has demonstrated amplification of nanosecond pulses in excess of 10 J at 10 Hz repetition rate with an opticalto- optical efficiency of 22%. The larger scale DiPOLE100 system, designed to deliver 100J temporally-shaped nanosecond pulses at 10 Hz repetition rate, has been developed at the CLF for the HiLASE project in the Czech Republic. Recent experiments conducted on the DiPOLE100 system demonstrated the energy scalability of the DiPOLE concept to the 100 J pulse energy level. Furthermore, second harmonic generation experiments carried out on the DiPOLE prototype confirmed the suitability of DiPOLE-based systems for pumping high repetition rate PW-class laser systems based on Ti:sapphire or optical parametric chirped pulse amplification (OPCPA) technology.
In this paper we provide an overview of the design of DiPOLE100, a cryogenic gas-cooled DPSSL system based on Yb:YAG multi-slab amplifier technology, designed to efficiently produce 100 J pulses, between 2 and 10 ns in duration, at up to 10 Hz repetition rate. The current system is being built at the CLF for the HiLASE project and details of the front end, intermediate 10J cryo-amplifier and main 100J cryo-amplifier are presented. To date, temporal and spatial pulse shaping from the front end has been demonstrated, with 10 ns pulses of arbitrary shape (flat-top, linear ramps, and exponentials) produced with energies up to 150 mJ at 10 Hz. The pump diodes and cryogenic gas cooling system for the 10J cryo-amplifier have been fully commissioned and laser amplification testing has begun. The 100J, 940 nm pump sources have met full specification delivering pulses with 250 kW peak power and duration up to 1.2 ms at 10 Hz, corresponding to 3 kW average power each. An intensity modulation across the 78 mm square flat-top profile of < 5 % rms was measured. The 100J gain media slabs have been supplied and their optical characteristics tested. Commissioning of the 100J amplifier will commence shortly.
In this work, we present measurements of efficiency-optimized 940 nm diode laser bars with long resonators that are
constructed with robustly passivated output facets at the Ferdinand-Braun-Institut (FBH). The measurements were
performed at room temperature on a test bench developed at HiLASE Centre, as a function of operating condition. The
single-diode bars generated < 1.0 kW when tested with 1 ms pulses at 1-10Hz operating frequency, corresponding to < 1
J per pulse. The maximum electrical-to-optical efficiency was < 60 %, with operating efficiency at 1 kW of < 50%,
limited by the ~ 200 μΩ resistance of the bar packaging. In addition, slow axis divergence at 1 kW was below 6° FWHM
and spectral width at 1 kW was below 7 nm FWHM, as needed for pumping Yb-doped solid state amplifier crystals.
A high average power cryogenically-cooled diode-pumped solid-state laser system for Hilase centre in Czech Republic is
being developed by Central Laser Facility at Rutherford Appleton Laboratory, England in collaboration with Hilase
team. The system will deliver pulses with energy of 100 J at 10 Hz repetition rate and will find applications in research
and industry. The laser medium and other elements of the system are subject to heavy thermal loading which causes
serious optical aberrations and degrade the output beam quality. To meet the stringent laser requirements of this kWclass
laser, it is necessary to implement adaptive optics system, which will correct for these aberrations. During our
research the sources of aberrations have been identified and analyzed. Based on this analysis, a suitable adaptive optics
system was proposed. After finalizing numerical models, simulations and optimizations, the adaptive optics system was
developed, characterized and installed in a cryogenically-cooled multi-slab laser system running up to 6 J and 10 Hz. The
adaptive optics system consists of 6x6 actuator bimorph deformable mirror and wavefront sensor based on quadriwave
lateral shearing interferometry operated in closed loop. The functionality of the system was demonstrated at full power.
An overview of Czech national R&D project HiLASE (High average power pulsed LASEr) is presented. The HiLASE project aims at development of pulsed DPSSL for hi-tech industrial applications. HiLASE will be a user oriented facility with several laser systems with output parameters ranging from a few picosecond pulses with energy of 5 mJ to 0.5 J and repetition rate of 1-100 kHz (based on thin disk technology) to systems with 100 J output energy in nanosecond pulses with repetition rate of 10 Hz (based on multi-slab technology).
Deformable mirrors have gained increasing interest in many different fields of application including laser physics, and they are becoming a universal tool for correcting optical aberrations of laser beams especially in large scale laser systems. One of the most common types of deformable mirror is a bimorph design which uses two plates of piezomaterial to which single electrodes are connected. These electrodes form the actuator array and their layout defines the resulting performance of the mirror to some extent. In the end all types of deformable mirrors currently used use an actuator array of some sort. To estimate the significance and effect of different actuator layout and shapes of actuators, an experimental study was performed. Four different commonly used actuator arrays were compared using photo-controlled deformable mirror. Using such device allows to study the effect of actuator layout separately from all other effects, since the device remains the same including all its imperfections. The experimental results are compared with numerical simulations and discussion is presented.
In this work, we present a comparative study of high power diode stacks produced by world’s leading manufacturers such as DILAS, Jenoptik, and Quantel. The diode-laser stacks are characterized by central wavelength around 939 nm, duty cycle of 1 %, and maximum repetition rate of 10 Hz. The characterization includes peak power, electrical-to-optical efficiency, central wavelength and full width at half maximum (FWHM) as a function of diode current and cooling temperature. A cross-check of measurements performed at HiLASE-IoP and Ferdinand-Braun-Institut (FBH) shows very good agreement between the results. Our study reveals also the presence of discontinuities in the spectra of two diode stacks. We consider the results presented here a valuable tool to optimize pump sources for ultra-high average power lasers, including laser fusion facilities.
We present an adaptive optics system for active wavefront correction of the first stage amplifier of a multi-slab laser system capable of generating 100 W of average output power and transverse dimensions of 20 mm x 20 mm. The results of this experiment are compared with numerical simulations.
Detailed modeling results of 100 J class laser systems with respect to the output energy, beam propagation, nonlinear phase accumulation, wavefront aberrations, and adaptive optics performance obtained in MIRÓ and MATLAB codes are presented here. The laser system is based on a cryogenically cooled Yb 3+ ∶YAG multislab amplifier with two identical amplifier heads and operates at 10 Hz repetition rate with an average power above 1 kW.
We present calculation of aberration compensation in high average power multi-slab laser by a deformable mirror. The calculations were compared with a simple experiment. For the calculations we have developed a code that works with a square-shaped piston driven push/pull deformable mirror with continuous facesheet and allows optimization of mirror parameters and actuator array geometry. We have corrected the calculated output wavefront of Hilase 10 J multi-slab laser system in MIRÓ by using several actuator array geometries. The numerical results were benchmarked on an experimental model of multi-slab chamber using a membrane deformable mirror.
We present the design parameters of a diode-pumped 100J-class multi-slab Yb:YAG laser at 10 Hz scalable to the kJ
regime. Results of detailed energetics and thermo-optical modeling confirm the viability of cryogenic helium-gas cooling approach to drastically reduce thermally-induced distortions in the laser slabs. In addition, a comparison of spectral measurements from laser-diode stacks and Yb:YAG crystals validates the feasibility of highly efficient diode-pumped solid-state lasers at cryogenic temperatures.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.