The laser-induced damage threshold (LIDT) of nematic liquid crystals is investigated in the femtosecond regime at 1030 nm. The thickness and breakdown of freely-suspended thin films (approximately 100 nm) of different mixtures (MLC2073, MLC2132 and E7) is monitored in real time by spectral-domain interferometry. The duration of laser pulses was varied from 180 fs to 1.8 ps for repetition rates ranging from single-shot to 1 MHz. The dependence of the LIDT with pulse duration suggests a damage mechanism dominated by ionization mechanisms at low repetition rate and by linear absorption at high repetition rate. In the single-shot regime, LIDTs exceeding 1 J/cm² are found for the three investigated mixtures.
We report on the status of the re-commissioning of a high energy OPCPA laser system with programmable spectrum that serves as a frontend for a 10 PW laser at ELI-Beamlines. The OPCPA chain was developed by a consortium of National Energetics and Ekspla along with scientists of ELI-Beamlines.1 The laser system, consisting of three picosecond OPCPA stages, pulse cleaner, Offner stretcher, and 5 nanosecond OPCPA stages pumped by Nd:YAG lasers with programmable pulse shape (NL944, Ekspla), allows for precise spectral shaping while achieving high nonlinear conversion efficiency. Employing a subsequent Nd:glass power amplifiers (PA), the system was demonstrated to yield>1 kJ of energy, while maintaining broad spectrum of > 13 nm (FWHM). After recommissioning the OPCPA frontend in Dolní Břežany, an output energy of 4.3 J, flat beam-profile and good far-field quality has been demonstrated. The spectral shape has been optimized to support > 15 nm bandwidth and >1.5 kJ, consistent with 10 PW operation of the fully integrated laser system after compression.
State-of-the-art physics experiments are pushing the development of lasers with ultra-high peak power pulses. 4 PW pulses have been produced with TiSa [1] and 10 PW with the same gain medium is scheduled at LULI (Apollon) and at ELI-NP.
The other approach is to use Nd-doped glass as gain medium, whose interest is in its capability of delivering higher energy at the expense of a longer pulse duration. Based on this gain material combined with an OPCPA based front-end, a kJ-10 PW class laser has been designed and built.
The front-end, consisting of picosecond OPCPA, temporal pulse cleaning and nanosecond OPCPA, delivers pulses with excess of 4 Joules at 5 Hz with a shaped spectrum to pre-compensate for gain distortions in Nd:glass power amplifiers. Two liquid-cooled, mixed glass power amplifiers, namely PA1 and PA2, are used for further amplification. Up to now, they have been activated demonstrating 70 J at 1 shot a minute after PA1 and 1 kJ at 1 shot every 7 minutes for PA2. The Fourier limit of the spectrum is 150 fs meaning 6 PW capability after compression.
This energy level has been obtained with only 3 Joules seed energy, from the OPCPA and partial activation of PA2. Scaling of this result suggests that more than 1.7 kJ should be obtained leading to 10 PW after compression while the output spectrum will remain compatible with 150 Fs thanks to the OPCPA spectral tailoring capability.
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 <15 fs pulses at 1 kHz repetition rate, is up and running. The L2 is a development line employing a 10 J / 10 Hz cryogenic gas-cooled pump laser which has recently been equipped with an advanced cryogenic engine. Operation of the L3-HAPLS system, using a gas-cooled DPSSL pump laser and a Ti:sapphire broadband amplifier, was recently demonstrated at 16 J / 28 fs, at 3.33 Hz rep rate. Finally, the 5 Hz OPCPA front end of the L4 kJ laser is up running and amplification in the Nd:glass large-aperture power amplifiers was demonstrated.
In this paper we are giving a summary of the Apollon 10 PW facility laser design together with updated laser
performance. The Apollon facility is currently under construction in France. The APOLLON laser system is a laser
designed for delivering pulses as short as 15 fs (10-15 s) with an energy exceeding 150 Joules on target. The peak power
delivered by this laser system will be 10 Petawatts (1016W). The Apollon laser system will be delivering 4 beams: one 10
PW beam (F1 beam 400 mm diameter), one 1 PW beam (F2 beam 140 mm diameter) and two additional probe beams
(F3 and F4) at a repetition rate of 1 shot per minute. The laser system is based on Ti-sapphire amplifiers pumped by
frequency doubled solid-state lasers. The repetition rate of the high energy part will be 1 shot per minute. The main beam
at the output of the last amplifier will be split and dispatched to two experimental areas. The main laser beam is
delivering 30 J before compression at a repetition rate of 1 shot per minute and we are currently increasing to get 100J.
In order to transport multi-petawatt (PW) femtosecond laser beams with large spectral bandwidth, specific mirrors have to be designed and manufactured. We report on an experimental study of the laser-damage resistance and other optical properties of coating materials deposited in a 1-m class coating chamber. The study is conducted on single-layer coatings deposited by electron beam evaporation at 500 fs. Based on the experience of large optics for nanosecond applications, hafnia and silica are particularly investigated. However, in the case of sub-15 fs, the spectral specifications for PW beam transport mirrors cannot be reached by classical high laser-resistant quarter-wave SiO2/HfO2 stacks. Therefore, we investigate the laser resistance of different dielectrics of interest deposited with electron-beam processes: Al2O3, Y2O3, Sc2O3, HfO2, Ta2O5, TiO2. The influence of multiple pulse irradiations and environmental conditions, such as vacuum and temperature, is studied. With the investigation of multilayer stacks, we also show that there is no difference in behavior when a film is studied as a single layer or embedded in a stack. Based on these results, we were able to optimize high reflective (>99.5%), broadband (300 nm) and high laser-induced damage threshold (2.5 J/cm2) mirrors for PW applications.
The peak power handling capability of ultra-short pulse lasers is main concern for new facilities, like those for the French Apollon 10P, and European Extreme Light Infrastructure (ELI) projects. Indeed, these last generation lasers require complex, large (Ø1m) and resistant optical components with optimized thin-film coatings. Using on one hand the recent development of high laser resistant broadband high reflective coatings through a joint project with the Laboratoire d’Optique Appliquée and Fresnel Institute, and on the other hand its long time experience with polishing and measuring large and complex optical components, Reosc decided to demonstrate the feasibility of a Ø500mm aperture, 90° deviation, F/2.5 high output NA Off-Axis Parabola (OAP) dedicated to focus fs ultra-intense laser beams.
The prototype of the 90° OAP has a concave surface with 20mm of aspherisation for focal length of F1250mm. The OAP is coated with a hybrid Metal/Multi-Layer-Dielectric coating. It provides a reflectivity up to 98%, an absolute Group Delay Dispersion (GDD) below 100fs² and a Laser-Induced Damage Threshold (LIDT) up to 0.5J/cm², at 15fs and under vacuum. These performances are achieved on the whole surface and on the 200nm spectral range required by the sub 20fs PW-systems.
In this paper, Reosc report the developments required for the polishing, the coating and the measurements of the OAP and we will show the performances achieved on the prototype.
Dielectrics as single layers and broadband high-reflective stacks were deposited by electron beam deposition
processes compatible with 1-meter class optics. After being physically and optically characterized, samples were
irradiated with several ultrafast lasers (KYW:Yb 500fs, Ti:Sa 40fs and Ti:Sa 11fs) with single and multi-pulses.
The setups of the test platforms, laser-induced damage threshold investigations of intrinsic materials, dielectric
multilayers and hybrid metal/dielectric multilayers and electric field intensity distributions are described.
In new laser facilities, broadband ultra-short pulses need to be transported in large and energetic beams to the experiment chambers through high performance optical components. We studied laser resistance of electronbeam- deposited materials in order to design meter scale high reflective optics according to petawatt-system requirements. We report intrinsic laser resistance of several dielectric materials, spectral performances of high reflective coatings and their laser induced damage threshold at different pulse durations from 150ps to 11fs.
Nowadays, more powerful and challenging laser systems are built to meet the need of evolving technology. In this
context, the aim of the HiLASE project [1] is to develop a multi-joule picosecond laser system working in kHz repetition
rate regime. The outputs of the project will provide not only unique source for both scientific and industrial applications,
but also great challenge for supporting technologies. The key parameter of all optical components in laser and beam
delivery structure is the laser induced damage threshold, which limits intensities manageable by the system. The
following paper presents results of LIDT test of mirrors intended to use in laser system built within the HiLASE project
as well as advanced LIDT test station design, which will use HiLASE laser as source.
Extreme Light Infrastructure (ELI), the first research facility hosting an exawatt class laser will be built with a joint
international effort and form an integrated infrastructure comprised at last three branches: Attosecond Science (in
Szeged, Hungary) designed to make temporal investigation at the attosecond scale of electron dynamics in atoms,
molecules, plasmas and solids. High Field Science will be mainly focused on producing ultra intense and ultra short
sources of electons, protons and ions, coherent and high energetic X rays (in Prague, Czech Republic) as well as laserbased
nuclear physics (in Magurele, Romania). The location of the fourth pillar devoted to Extreme Field Science, which
will explore laser-matter interaction up to the non linear QED limit including the investigation of vacuum structure and
pair creation, will be decided after 2012. The research activities will be based on an incremental development of the light
sources starting from the current high intensity lasers (APOLLON, GEMINI, Vulcan and PFS) as prototypes to achieve
unprecedented peak power performance, from tens of petawatt up to a fraction of exawatt (1018 W). This last step will
depend on the laser technology development in the above three sites as well as in current high intensity laser facilities.
We present a novel architecture of deformable mirror dedicated to lasers. The new monomorph mirror presents the advantage of avoiding high spatial frequency on the residual wavefront enabling propagation of the laser beam without any energy modulation. The obtained residual wavefront is 3.4 nm rms wavefront.
Since the beginning of the 90's the generation of high-intense laser pulses has known an unprecedented evolution thanks to the conjunction of the possibility of the Chirped Pulse Technique and the availability of spectrally broad-band laser media. Lasers capable of producing petawatt pulses can now be built on few optical tables in a small laboratory. We review the generation and the amplification of ultra-short pulses by the Chirped Pulse Amplification technique.
We demonstrate a femtosecond laser chain that generates 20 TW at 10 Hz in less than 50 fs with focused intensities higher than 3 X 1019 W/cm2. This system is optimized for a broad transmission bandwidth and includes an aberration-free stretcher compressor.
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.