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Modern laser plasma accelerators require combination of high peak power and high average power from the laser. Ti:Sa CPA remaining the best technology for such purpose a high average power Ti:Sa amplifier has been developed

As major milestone of commissioning phase of beam transport section for the 10 PetaWatts beamlines of Extreme Light Infrastructure Nuclear Physics (ELI-NP) located in Magurele (Romania), we have propagated the beam throughout the beam transport section and measured its energy as well as its pulse duration after compression at full energy and full aperture. 10 consecutive laser pulses have been shot at a repetition rate of 1 shot per minute with compressed pulse energy ranging between 241 and 246 Joules while pulse duration has been measured at 23 fs leading to the first ever operation above 10 PetaWatts peak power

Processes using laser-shock applications, such as Laser Shock Peening or Laser Stripping require a deep understanding of both mechanical and thermal loading applied. We hereby present new experimental measurements of the plasma pressure release regarding its initial dimension, which depends on the laser beam size. Our data were obtained through shock waves’ velocity analysis and radiometric assessments. A new model to describe the adiabatic release behavior of a laser-induced plasma with a dependency to the beam size is developed. The results and the associated model exhibit that the plasma release duration is shortened with smaller laser spots. As a consequence, with chosen smaller laser spots (0.6 mm to 1 mm), the thermal loading applied during the plasma lifetime will also decrease. These new results shall help for a better understanding of laser-matter interaction for laser-shock applications by giving more accurate plasma profiles. Thus, process simulations can be improved as well. Eventually, by considering recent developments with high-power Diode Pumped Solid-State lasers (DPSS), we now expect to develop a new configuration for LSP which could be applicable both without any thermal coating and deliverable by an optical fiber. This research was funded by Thales company, institutions (CEA,NRS, ENSAM), and by the ANR (Agence Nationale de la Recherche), Forge Laser Project (Grant No.: ANR-18-CE08-0026).

Using most advanced Diode-Pumped Solid State laser architectures (1 J, 10 ns, 200 Hz), we have developed and optimized a high-frequency configuration for Laser Shock Peening: small laser spots, high-overlap ratios and without thermal coating.

European physical journal special topics 229(24), 3675 - 4284 (2020). doi:10.1140/epjst/e2020-000127-8, This report presents the conceptual design of a new European research infrastructure EuPRAXIA. The concept has been established over the last four years in a unique collaboration of 41 laboratories within a Horizon 2020 design study funded by the European Union. EuPRAXIA is the first European project that develops a dedicated particle accelerator research infrastructure based on novel plasma acceleration concepts and laser technology. It focuses on the development of electron accelerators and underlying technologies, their user communities, and the exploitation of existing accelerator infrastructures in Europe. EuPRAXIA has involved, amongst others, the international laser community and industry to build links and bridges with accelerator science — through realising synergies, identifying disruptive ideas, innovating, and fostering knowledge exchange. The Eu-PRAXIA project aims at the construction of an innovative electron accelerator using laser- and electron-beam-driven plasma wakefield acceleration that offers a significant reduction in size and possible savings in cost over current state-of-the-art radiofrequency-based accelerators. The foreseen electron energy range of one to five gigaelectronvolts (GeV) and its performance goals will enable versatile applications in various domains, e.g. as a compact free-electron laser (FEL), compact sources for medical imaging and positron generation, table-top test beams for particle detectors, as well as deeply penetrating X-ray and gamma-ray sources for material testing. EuPRAXIA is designed to be the required stepping stone to possible future plasma-based facilities, such as linear colliders at the high-energy physics (HEP) energy frontier. Consistent with a high-confidence approach, the project includes measures to retire risk by establishing scaled technology demonstrators. This report includes preliminary models for project implementation, cost and schedule that would allow operation of the full Eu-PRAXIA facility within 8—10 years., Published by Springer, Heidelberg

We report a full experimental comparison study on the injection of a Ti:Sa multi-terawatt amplifier chain with a standard 15 fs Ti:Sa oscillator and 35 fs frequency-doubled fiber oscillator. The study highlights that the Ti:Sa oscillator, with high performance in terms of pulse duration and spectral width, can be replaced by the frequency-doubled fiber oscillator to seed Ti:Sa amplifier chains almost without any compromise on the output pulse duration and picosecond contrast. Finally, we demonstrate for the first time to our knowledge a 30 TW and 33 fs Ti:Sa amplifier injected by a fiber oscillator.

We report the generation of unprecedented 10 PetaWatt laser pulses obtained from each of the two beamlines of the High Power Laser System (HPLS) of ELI-NP (Extreme Light Infrastructure – Nuclear Physics) research infrastructure. The laser system is a hybrid system made of a double CPA based on amplification within Titanium Sapphire crystals combined with an OPCPA with a parametric amplification stage boosting the energy to 10 mJ at the entrance of the second CPA. A XPW filter is also inserted between the two CPA and in combination with the OPCPA improves the temporal contrast of the pulses by typically 7 orders of magnitude. The spectral effects occurring during amplification such as gain narrowing and wavelength shifting are compensated through the use of spectral filters. Final amplification stages are involving large aperture Ti:Sapphire crystals (up to 200 mm) which are pumped by high energy frequencydoubled Nd:Glass lasers delivering each 100 J of green light. Laser beams have been amplified respectively up to 332 J and to 342 J of pulse energy at 1 shot per minute without any occurrence of ASE and transverse lasing thanks to index matching fluid surrounding the crystal over is entire length and pump deposition management over the time before each beam pass within the Ti:Sapphire crystal. We have demonstrated full aperture compression by metric gratings of these amplified pulses down to 22.6 fs and therefore made the full demonstration for the first time ever of 10 PW capability from a laser system.

We report on a two-arm hybrid high-power laser system (HPLS) able to deliver 2 × 10 PW femtosecond pulses, developed at the Bucharest-Magurele Extreme Light Infrastructure Nuclear Physics (ELI-NP) Facility. A hybrid front-end (FE) based on a Ti:sapphire chirped pulse amplifier and a picosecond optical parametric chirped pulse amplifier based on beta barium borate (BBO) crystals, with a cross-polarized wave (XPW) filter in between, has been developed. It delivers 10 mJ laser pulses, at 10 Hz repetition rate, with more than 70 nm spectral bandwidth and high-intensity contrast, in the range of 1013:1. The high-energy Ti:sapphire amplifier stages of both arms were seeded from this common FE. The final high-energy amplifier, equipped with a 200 mm diameter Ti:sapphire crystal, has been pumped by six 100 J nanosecond frequency doubled Nd:glass lasers, at 1 pulse/min repetition rate. More than 300 J output pulse energy has been obtained by pumping with only 80% of the whole 600 J available pump energy. The compressor has a transmission efficiency of 74% and an output pulse duration of 22.7 fs was measured, thus demonstrating that the dual-arm HPLS has the capacity to generate 10 PW peak power femtosecond pulses. The reported results represent the cornerstone of the ELI-NP 2 × 10 PW femtosecond laser facility, devoted to fundamental and applied nuclear physics research.

The demonstration of the first 10 PW pulses during March 2019 the High Power Laser System at ELI-NP together with extensive tests, provides now the possibility to evaluate the ultrahigh irradiance in reach.

Figure 20.1 was not correct in the published article. The original article has been corrected. The published apologizes for the inconvenience.

Mid-infrared milli-joule level table-top sources are known to be key enabling tool for the development of next level multi-kilo-electron-volt coherent X-ray sources [1] as well as the study of extreme photonics in the mid-infrared regime [2]. Moreover, due to the ultra-broadband bandwidth they cover an important range of live molecular fingerprint regions [3].

Titanium-doped sapphire (Ti:Al 2 O 3 ) is a gain medium with a very broad emission bandwidth allowing the generation and amplification of very short pulses (<

We report first 10 PW light from the ELI-NP laser. We have obtained at 1 shot/min pulses with 332 J energy before compression and 22.3 fs duration leading to a peak power of 10.9 PW.

We present the state of the art of a compact high-energy mid-infrared laser system for TW-level 8-cycle pulses at 7 um. This system consists of an Er:Tm:Ho:fiber MOPA which serves as the seeder for a ZGP-based OPCPA chain in addition to a Ho:YLF amplifier which is Tm:fiber pumped. Featuring all-optical synchronization, the system delivers 260-mJ pump energy at 2052 nm, 16-ps duration at 100 Hz with a stability of 0.8 % rms over 20 min. We show that chirp inversion in the OPCPA chain leads to excellent energy extraction and aids in compression of the 7-um pulses to 8 optical cycles (188 fs) in bulk BaF2 with 93.5 % efficiency. Using 21.7 mJ of the available pump energy, we generate 0.75-mJ-energy pulses at 7 um due to increased efficiency with a chirp-inversion scheme. The pulse quality of the system's output is shown by generating high harmonics in ZnSe which span up to harmonic order 13 with excellent contrast. The combination of the passive carrier-envelope phase stable mid-infrared seed pulses and the high-energy 2052 nm picosecond pulses makes this compact system a key enabling tool for the next generation of studies on extreme photonics, strong field physics and table-top coherent X-ray science., Comment: 4 pages, 5 figures

International audience; We report on the coherent beam combining of seven fiber chirped-pulse amplifiers using a highly scalable architecture. A combining efficiency of 48% is obtained in linear regime, yielding 71 W pump-limited average power after compression, with a phase noise between two fibers as low as λ/38 RMS. The experiment is operated at high B-integral, with only little impact on the combining efficiency as well as on the temporal and spatial properties of the combined beam.

We report on the demonstration of a symmetrically cooled thin-disk laser concept using Ti:sapphire for the gain medium and plano-convex shaped single crystal diamond as intracavity heat spreaders. This allowed us to increase the absorbed pump intensity by at least a factor of five compared to a previously reported Ti:sapphire thin-disk oscillator.

International audience; We report on the coherent combination of seven fiber amplifiers in the femtosec-ond regime using an interferometric phase measurement technique. A combination efficiencyof 54 % and a compressed pulse length of 225 fs were achieved.

We report on a novel laser concept with symmetrical cooling of a Ti:sapphire thin-disk using transparent heat spreaders made out of large area single-crystal diamond. First results of laser operation are presented.

We report on the generation of 260-mJ pulses at 2 µm wavelength from a Ho:YLF MOPA system for pumping a millijoule-class 7-µm OPCPA.

A new conduction cooled compact laser for SuperCam LIBS-RAMAN instrument aboard Mars 2020 Rover is presented. An oscillator generates 30mJ at 1µm with a good spatial quality. A Second Harmonic Generator (SHG) at the oscillator output generates 15 mJ at 532 nm. A RTP electro-optical switch, between the oscillator and SHG, allows the operation mode selection (LIBS or RAMAN). Qualification model of this laser has been built and characterised. Environmental testing of this model is also reported.

A new conduction cooled compact laser for SuperCam LIBS-RAMAN instrument aboard Mars 2020 Rover is presented. An oscillator generates 30mJ at 1µm with a good spatial quality. A Second Harmonic Generator (SHG) at the oscillator output generates 15 mJ at 532 nm. A RTP electro-optical switch, between the oscillator and SHG, allows the operation mode selection (LIBS or RAMAN). Qualification model of this laser has been built and characterised. Environmental testing of this model is also reported.

International audience; We report the first coherent combination of seven fiber amplifiers in thefemtosecond regime using an interferometric phase measurement. Details of the setup will bepresented, as well as first results evaluating the combination efficiency.

Les lasers de tres forte energie et de tres forte puissance moyenne sont par leurs caracteristiques memes des lasers extremes utilises pour des applications extremes. A cote des enormes installations destinees a la production d’energie, de nombreux lasers « a taille humaine » existent aujourd’hui dans les laboratoires, tirant parti de plusieurs decouvertes fondamentales dans les technologies laser.

The XCAN project, which is a three years project and began in 2015, carried out by Thales and the Ecole Polytechnique aims at developing a laser system based on the coherent combination of laser beams produced through a network of amplifying optical fibers. This technique provides an attractive mean of reaching simultaneously the high peak and high average powers required for various industrial, scientific and defense applications. The architecture has to be compatible with very large number of fibers (1000-10000). The goal of XCAN is to overcome all the key scientific and technological barriers to the design and development of an experimental laser demonstrator. The coherent addition of multiple individual phased beams is aimed to provide tens of Gigawatt peak power at 50 kHz repetition rate. Coherent beam combining (CBC) of fiber amplifiers involves a master oscillator which is split into N fiber channels and then amplified through series of polarization maintaining fiber pre-amplifiers and amplifiers. In the so-called tiled aperture configuration, the N fibers are arranged in an array and collimated in the near field of the laser output. The N beamlets then interfere constructively in the far field, and give a bright central lobe. CBC techniques with active phase locking involve phase mismatch detection, calculation of the correction and phase compensation of each amplifier by means of phase modulators. Interferometric phase measurement has proven to be particularly well suited to phase-lock a very large number of fibers in continuous regime. A small fraction of the N beamlets is imaged onto a camera. The beamlets interfere separately with a reference beam. The phase mismatch of each beam is then calculated from the interferences’ position. In this presentation, we demonstrate the phase locking of 19 fibers in femtosecond pulse regime with this technique. In our first experiment, a master oscillator generates pulses of 300 fs (chirped at 200 ps). The beam is split into 19 passive channels. Prior to phase locking, the optical path differences are adjusted down to 10 μm with optical delay lines. Interferograms of the 19 fibers are recorded at 1 kHz with a camera. A dedicated algorithm is developed to measure both the phase and the delay between the fibers on a measurement path. The delay and phase shift are thus calculated collectively from a single image and piezo-electric fiber stretchers are controlled in order to ensure compensation of time-varying phase and delay variations. The residual phase shift error is below λ/60 rms. The coherent beam combining is obtained after propagation and compression. The combined pulse width is measured at 315fs. A second experiment was done to coherently combine two amplified channels of the XCAN demonstrator. A residual phase shift error of λ/30 rms was measured in this case.

The development of coherent light sources with emission in the mid-IR is currently undergoing a remarkable revolution. The mid-IR spectral range has always been of tremendous interest, mainly to spectroscopists, due to the ability of mid-IR light to access rotational and vibrational resonances of molecules which give rise to superb sensitivity upon optical probing [1-3]. Previously, high energy resolution was achieved with narrowband lasers or parametric sources, but the advent of frequency comb sources has revolutionized spectroscopy by providing high energy resolution within the frequency comb structure of the spectrum and at the same time broadband coverage and short pulse duration [4-6]. Such carrier to envelope phase (CEP) controlled light waveforms, when achieved at ultrahigh intensity, give rise to extreme effects such as the generation of isolated attosecond pulses in the vacuum to extreme ultraviolet range (XUV) [7]. Motivated largely by the vast potential of attosecond science, the development of ultraintense few-cycle and CEP stable sources has intensified [8], and it was recognized that coherent soft X-ray radiation could be generated when driving high harmonic generation (HHG) with long wavelength sources [9-11]. Recently, based on this concept, the highest waveform controlled soft X-ray flux [12] and isolated attosecond pulse emission at 300 eV [13] was demonstrated via HHG from a 1850 nm, sub-2-cycle source [14]. Within strong field physics, long wavelength scaling may lead to further interesting physics such as the direct reshaping of the carrier field [15], scaling of quantum path dynamics [16], the breakdown of the dipole approximation [17] or direct laser acceleration [18]. The experimental development of long wavelength light sources therefore holds great promise in many fields of science and will lead to numerous applications beyond strong field physics and attosecond science. In this paper, we present the first mid-IR optical parametric chirped pulse amplifier (OPCPA) operating at a center wavelength of 7 μm with output parameters suitable already for strong-field experiments. It is also the first demonstration of an Optical Parametric Chirped Pulse Amplifier (OPCPA) using a 2 μm laser pump source which enables the use of non-oxide nonlinear crystals with typically limited transparency at 1 mm wavelength. This new OPCPA system is all-optically synchronized and generates 0.55 mJ energy, CEP stable optical pulses. The pulses are currently compressed to sub-8 optical cycles but support a sub-4 cycle pulse duration. The discrepancy in compression is due to uncompensated higher order phase from the grating compressor which will be addressed in the future.

A hybrid Ti:Sa CPA/BBO OPCPA system with a XPW filter in between the two has been developed to produce a broadband high contrast seeder of 10 mJ for the two 10 PetaWatt beamlines of ELI NP infrastructure.

A laser system made of two beams of 10 PW each has been designed and is currently built for ELI-NP research infrastructure. Design is presented as well as preliminary results up to the 1PW level amplifier.

We present the first ultrafast and all-fiber pumped OPCPA operating at 7 μm and generating 0.55 mJ pulses at 180 fs (7.7 optical cycles).

We present a novel all-fiber pumped optical parametric chirped pulse amplifier (OPCPA) architecture to generate self-carrier-to-envelope-phase stable, sub-eight-optical-cycle duration pulses at 7 μm wavelength approaching millijoulelevel pulse energy at 100 Hz repetition rate. The system yields a peak power of 1.1 GW and, if focused to the diffraction limit, would reach a peak intensity of 7 × 1014 W∕cm2. The OPCPA is pumped by a 2 μm Ho:YLF chirped pulse amplifier to leverage the highly efficient and broadband response of the nonlinear crystal ZGP. The 7 μm seed at 100 MHz is generated via difference frequency generation from an Er:Tm:Ho multi-arm fiber frequency comb, and a fraction of its output optically injects the Ho:YLF amplifier. While the pulse bandwidth at 7 μm is perfectly suited for nonlinear and spectroscopic applications, current parameters offer, for the first time, to the best of our knowledge, the possibility to explore strong-field physics in an entirely new wavelength range with a ponderomotive force 77 times larger than from an 800 nm source. The overall OPCPA system is very compact and provides a new tool for investigations directly in the molecular fingerprint region of the electro-magnetic spectrum or to drive high harmonic generation to produce fully coherent x-rays in the multi-kiloelectron-volt range and possibly zeptosecond temporal waveforms.

The XCAN collaboration program between the Ecole Polytechnique and Thales aims at developing a laser system based on the coherent combination of several tens of laser beams produced through a network of amplifying optical fibers [1]. As a first step this project aspires to demonstrate the scalability of a combining architecture in the femtosecond regime providing high peak power with high repetition rate and high efficiency. The initial system will include 61 individual phased beams aimed to provide 10 mJ, 350 fs pulses at 50 kHz.

ATLAS 100, a compact high energy laser delivering more than 100 joules at the repetition rate of 1 shot per minute has been developed for the two 10 PetaWatt beamlines of ELI NP infrastructure.

A novel class of high energy ultrafast OPCPA system at 7 μm, pumped by an optically synchronized and Tm:fiber pumped 2 μm picosecond Ho:YLF CPA system, delivers mJ-level pulses supporting a sub-4 optical cycle duration.

A hybrid Ti:Sa CPA/BBO OPCPA system with a XPW filter inbetween the two has been developed to produce a broadband high contrast seeder of 10 mJ for the two 10 PetaWatt beamlines of ELI NP infrastructure.

We review the recent results achieved on industrial grade Titanium Sapphire PetaWatt lasers demonstrating clear improvements. Key enabling technologies are presented. Perspectives towards higher peak power of 10 PW are discussed.

We describe a Titanium:Sapphire based PetaWatt laser delivering pulses of peak power reaching 1.1 PetaWatt with an unprecedented pulse width as low as 24.2 fs at a repetition rate of 0.1 Hz

International audience

Within the framework of a European project, three cleaning laser devices are tested to evaluate the influence of different parameters on stone cleaning rate and efficiency. The project objective is to design a large surface-cleaning laser. One of the devices is a prototype with some technological improvements compared to the lasers used today for restoration. The tests are performed on limestone and sandstone covered with various dirt layers. The influence of fluence, water spraying, spot area, frequency, as well as particle emission rate is investigated. Results allow a comparison of the importance of each parameter and confirm the increase in cleaning speed of the new prototype. Nevertheless, it can be concluded that an automatic device will be suitable to attain a cleaning speed competitive with other traditional cleaning techniques.

Ultra high intensity laser pulses are required by researchers for a growing number of applications such as laser-based particle acceleration for generation of ultrafast energetic electrons [1], laser based ion acceleration and attosecond light pulse generation.

We describe the design and performance of a PW laser based on Ti:Sa operating at an unprecedented pulse width of 23.7 fs at a repetition rate of 0.1 Hz. Energy and pulse duration measurements demonstrate a potential peak power of 1.12 PW

Transverse parasitic lasing is well known for limiting the signal gain and the pulse energy that can be extracted from Ti:sapphire petawatt amplifiers. We have developed a technique for suppressing these parasitic lasing modes based on perfect refractive index-matching liquid doped with a broad-bandwidth absorber to suppress the transverse lasing while ensuring proper heat removal from the Ti:sapphire crystal. The 800 nm laser output with a bandwidth of 41 nm (FWHM) and peak energy of 22.7 J at a repetition rate of 1 Hz is demonstrated.

We have obtained 23 J uncompressed laser pulses at a repetition rate of 1 Hz with a spectral width of 41 nm FWHM which could produce 600 TW if compressed ; this is the highest energy obtained to date from a Titanium Sapphire amplifier working at a such repetition rate. This amplifier is part of a 1.3 PW laser system under construction by Thales Optronique for the BELLA project of LBNL aiming laser wakefield acceleration of electrons up to 10 GeV.

We describe design and performance of a PetaWatt laser based on Titanium Sapphire and working at an unprecedented repetition rate of 1 Hz. Preliminary results indicate an energy of 22 J before the final amplifier.

We present a two stages Ti:Sapphire amplifier system running at 1Hz reaching up to 65J supporting sub-30fs pulses. Extreme care have been taken on the beam profile quality as well as preventing transverse lasing.

We report on an experimental investigation of the noise properties of an free-running, high-power, picosecond Nd:YVO 4 oscillator pumped by a 100 W laser diode. The amplitude noise has been measured with a photodiode and an electronic spectrum analyser, and then compared with other mode-locked oscillator's noise spectrum. We show that in terms of noise properties, our powerful oscillator is comparable with low-power oscillators such like low-noise Ti:Sapphire oscillators. We also show that the frequency doubling does not affect the amplitude noise of the oscillator. High power diode pumping is then not an issue to get low-noise high-power oscillators.

Amplification of large bandwidth pulses in a spatio-temporal configuration is demonstrated at 28 mJ for avoiding spectral shifting in high energy power amplifiers in CPA laser chain. Application to hundreds joules pulses will be discussed.

We report on a high-power passively mode-locked TEM(00)Nd:YVO(4) oscillator, 888 nm diode-pumped, with pulse durations adjustable between 46 ps and 12 ps. The duration tunability was obtained by varying the output coupler (OC) transmission while avoiding resorting to spatial hole burning (SHB) for pulse shortening. At a repetition rate of 91 MHz and for an output power ranging from 15 Wto45 W, we produced SHB-free 12-ps-to32-ps-long pulses. Within this range of power, these are the shortest pulse durations obtained directly from Nd:YVO(4) oscillators.

We report on a high-power, passively mode-locked, TEM 00 Nd:YVO 4 oscillator with adjustable pulse duration between 46 and 12ps. The laser is end-pumped by an 888nm laser diode and mode-locking is achieved with a semiconductor saturable absorber mirror (SESAM). The laser has a repetition rate of 91MHz and the M 2 beam quality factor is better than 1.2 at 15ps. At the optimum output coupler, it provides a maximum average output power of 45W with 32ps pulse duration. In literature, the presence of spatial hole burning (SHB) often helps to shorten the pulse length down to few picoseconds. However, SHB might be an issue for some specific application requiring e.g. low noise picosecond oscillators. In this contribution, we demonstrate that it is possible to shorten the pulse duration by lowering the intracavity losses without SHB. Pulse tunability from 46 to 12ps is achieved by changing the output coupler of the cavity while staying in the continuous-wave mode-locked regime. Pulse duration is almost linear with the output coupler transmission and increases from 12 to 32ps with average output power ranging from 15 to 45W. In this range of output power, we demonstrate the shortest pulses directly from a Nd:YVO 4 oscillator.

We report on a high-average-power 888nm diode-pumped passively mode-locked TEM 00 Nd∶YVO 4 oscillator with adjustable pulse durations. From 45 to 15W output power, we produced corresponding 32 to 12ps long pulses without spatial hole burning.

Compact X-rays sources raise a great enthusiasm in life sciences for applications such as protein crystallography, medical imaging or radiotherapy. Such X-rays can be produced by Thomson scattering of photons coming from a laser source colliding with electrons. However, Thomson scattering is very inefficient. Real-world life science on-site applications requiring high X-rays flux, a scheme based on a mode-locked picosecond laser injected in a Fabry-Perot cavity combined with an electron storage ring has been explored [1]. This technology can be pushed-up with a powerful high repetition-rate mode-locked laser injected in a high finesse cavity enabling to reach the intracavity average power up to few hundreds of kW required by the medical applications. The design of the laser system can then be based either on a low power oscillator combined with a relatively sophisticated high gain amplifier, or on a powerful oscillator seeding a low gain amplifier. However, a powerful single oscillator delivering a few tens of Watts average power with 15–20 ps pulses coupled with a 1000 gain Fabry-Perot cavity would be sufficient as a demonstrator for imaging application. Therefore, in this contribution, we propose a design for a 20W-sub-20 ps class mode-locked Nd:YAG oscillator.

Summary form only given. Q-switched solid-state oscillators are attractive due to their compactness, stability and high efficiency. High average power frequency conversion of these systems is commonly performed intracavity. Owing to pulse peak powers up to 500 kW the developed system is suitable for external high average power frequency doubling. We present the Nd:YAG laser rod resonator design, and show CW and Q-switching operation. External frequency doubling is achieved using a Type II flux grown KTiOPO/sub 4/ crystal.