This PDF file contains the front matter associated with SPIE Proceedings Volume 10084, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

The Laser Megajoule facility, developed by the CEA is designed to provide the experimental capabilities to study high density plasma physics. The 176 Nd:glass laser beams of the facility will deliver a total energy of 1.4MJ of UV light at 0.35 μm and a maximum power of 400 TW. The laser beams are focused on a micro-target inside a 10-meter diameter spherical chamber.

A first bundle of eight laser beams was officially commissioned in October 2014. Since then, several experimental campaigns have been carried out, to qualify LMJ experimental capability and to validate radiative hydrodynamics simulations. New target diagnostics were installed around the target chamber for that purpose.

The installation of new bundles is continuing, simultaneously to the physics experiments. A second control room has been dedicated to the first steps of every bundle integration.

In parallel with the assembly of the bundles, the laser process is continuously improving (low contrast beam profile, upgraded chamber center reference, improved focal spot profile).

Second bundle commissioning has been achieved at the end of 2016 with some physics experiments using the 16 operational beams.

The LMJ facility is now operational with two bundles (16 beams) and the bundle commissioning rhythm is increasing. The present performances meet the needed requirements for the physics experiments. We are currently integrating new bundles, increasing the LMJ laser beam energy, and installing new diagnostics in order to achieve the next configurations.

This talk will provide an overview of high power laser research at Lawrence Livermore National Laboratory (LLNL). It will discuss the status of the National Ignition Facility (NIF) laser. In addition, the talk will describe other laser development activities such as the development of high average power lasers and novel fiber lasers.

The National Ignition Facility (NIF) has been in service since 2007 and operating with > 1 MJ energies since 2009. During this time the facility has transitioned to become an international user facility and increased the shot rate from ~150 target shots per year to greater than 400 shots per year. Today, the NIF plays an essential role in the US Stockpile Stewardship Program, providing data under the extreme conditions needed to validate computer models and train the next generation of stockpile stewards. Recent upgrades include the Advanced Radiographic Capability (ARC), a high energy short pulse laser used to do high resolution radiography.

In addition to the NIF, this talk will include an overview of progress on the high average power laser development, recent results from fiber laser development activities and improvements to laser design and computational capabilities.

A new high power laser facility with 8 beams and maximum output energy of one beam 5kJ/3.4ns/3ω has been performed and operated since 2015. Combined together the existing facilities have constructed a multifunction experimental platform including multi-pulse width of ns, ps and fs and active probing beam, which is an effective tool for Inertial Confinement Fusion (ICF) and High Energy Density (HED) researches. In addition another peculiar high power laser prototype pushes 1ω maximum output energy to 16kJ in 5ns and 17.5kJ in 20ns in flat-in-time pulse, this system is based on large aperture four-pass main amplifier architecture with 310mm×310mm output beam aperture. Meanwhile the near field and far field have good quality spanning large energy scope by use of a wide range of technologies, such as reasonable overall design technique, the integrated front end, cleanness class control, nonlinear laser propagation control, wave-front adaptive optics and precision measurement. Based on this excellent backup, 3ω damage research project is planning to be implemented. To realize the above aims, the beam expanding scheme in final transport spatial filter could be adopted considering tradeoff between the efficient utilization of 1ω output and 3ω damage threshold. Besides for deeply dissecting conversion process for beam characteristic influence of 1ω beam, WCI (Wave-front Code Image) instrument with refined structure would be used to measure optical field with simultaneous high precision amplitude and phase information, and what’s more WCI can measure the 1ω, 2ω and 3ω optical field in the same time at same position, so we can analyze the 3ω beam quality evolution systematically, and ultimately to improve the 3ω limited output.

In a word, we need pay attention to some aspects contents with emphasis for future huger laser facility development. The first is to focus the new technology application. The second is to solve the matching problem between 1ω beam and the 3ω beam. The last is to build the whole effective design in order to improve efficiency and cost performance.

Accurate characterization of pulse contrast for high peak power lasers is critical to the success of experiments exploring inertial confinement fusion. The Advanced Radiographic Capability (ARC) laser at the National Ignition Facility (NIF) is a petawatt class laser system that produces pulses in the picosecond regime for the creation of diagnostic x-rays. ARC leverages four of the NIF’s beamlines for final amplification while implementing a separate front-end and pre-amplification stage, known as the High-Contrast ARC Front End (HCAFE). To characterize pulse contrast at the output of HCAFE, a means of measurement at long times (>500 ps) has been developed using a photodiode that has achieved a dynamic range of over 100 dB and 125 dB after deconvolution. Within hundreds of picoseconds of the main pulse, a commercial third-order cross-correlator (Amplitude Technologies Sequoia) is used to characterize the pulse contrast. Together, these diagnostics provide the necessary data for ensuring pulse contrast requirements can be met on ARC. Efforts were made to mitigate existing pre-pulses and to increase the stability of the system as a long-term operational companion to the NIF.

We describe the development and testing of the photodiode diagnostic and the analysis of the data resulting from contrast measurements. Details are also provided regarding the identification and mitigation of pre-pulses within the HCAFE system.

We report on testing of an edge-pumped ceramic Yb:YAG disk laser for pulse amplification under intense pumping. The disk has a composite construction with Yb-doped central portion cosintered with an undoped perimetral edge. Light from multi-kW pulsed diodes is transported though the disk edge and absorbed in the Yb-doped center. This configuration results in a very simple and compact laser gain module. The disk is operated as a storage amplifier. Amplified spontaneous emission and parasitic lasing is alleviated by the geometry of the laser disk edge rather than absorption cladding. Our test results indicate that this approach offers a robust mitigation of ASE. This work presents results of stored energy, gain, and ASE mitigation in the Yb:YAG disk laser under intense pumping.

Two types of the large bimorph deformable mirrors with the size of 410x468 mm and 320 mm were developed and tested. The results of the measurements of the response functions of all the actuators and of the surface shape of the deformable mirror are presented in this paper. The study of the mirror with a Fizeau interferometer and a Shack- Hartmann wavefront sensor has shown that it was possible to improve the flatness of the surface down to a residual roughness of 0.033 μm (RMS). The possibility of correction of the aberrations in high power lasers was numerically demonstrated.

This paper presents the design and simulation of Laser power beaming (LPB) system that establishes an optimal power transmission path based on the received signal strength. LPB system is possible to transfer power from multiple transmitters to a single receiver to the characteristics of the laser and the solar panel. When the laser beam from multiple transmitters aimed at a solar panel at the same time, the received power is the sum of all energy at a solar panel. Our proposed LPB system consists of multiple transmitter and multiple receivers. The transmitter sends its power characteristics as optically modulated pulses and powers as high-intensity laser beams. Using the attenuated power level, the receiver can estimate the maximum receivable powers from the transmitters and select optimal transmitters. Throughout the simulation, we will verify that it is possible that different LPB receivers were achieved their required power by the optimal allocation of the transmitter among the different transmitters.

Laser damage resistance is a key factor for the improvement of high power laser system. The PETAL laser, developed by the CEA-CESTA (France), uses meter scale reflective optics to compress, transport and focalize sub-picosecond laser pulses at 1053nm with high-energy [1]. In the case of defect-free material, laser-induced damage in the sub-picosecond regime is known to be deterministic since the threshold depends only on the electronic structure of the irradiated materials, the pulse duration and the enhancement of the electric fields in thin film coatings. Based on this consideration, a mono-shot technique has been investigated to assess the intrinsic damage resistance of optical component with only one laser shot. On the other hand, while considering real optical components, manufacturing processes included nanoscale defects in the functional coating. These defects can be ejected when irradiated and strongly reduce the laser damage resistance of optics: rasterscan procedure has then been developed to determine defect-induced damage densities. These densities are found to be high even for fluences well below the intrinsic Laser-Induced Damage Threshold and they increase with the fluence. These experiments bring new information on the operating characteristics of optics in short pulse regime. Once damage is triggered, its evolution under subsequent irradiations has also been studied. Growth experiments have been compared to numerical simulations. The investigations on growth behavior allow a better estimation of the functional lifetime of an optic in its operating conditions. The whole of results, damage initiation and damage growth, is discussed to the light of the laser damage observed on PETAL optics.

Beam-guiding system (BGS) in the target area of a laser-driver maps the rectangular arrangement at the main lasers to a spherical geometry configuration of shooting lasers at the target chamber. It also ensures that all the laser beams share the same light path length when they arrive at the target chamber center. With the output energy raising from 2MJ to 5MJ@3ω, the laser beam quantity will increase to more than 500. In this situation, researches were conducted on the relationship among the beam quantity, beam combination fashion in the target area and the radius of the target chamber. Also, beam transmission units (BTU), including transmission models of main lasers and shooting lasers and the switch manner between them, was put forward to simply the BGS arrangement work. Then we discussed the factors that determine the BTU configuration and general target area shape. Based on the beam combination fashion and BTU, the entire BGS arrangement in the target area of a 5.76MJ@3ω indirect-drive laser facility with 576 laser beams was figured out.

Enhancing performance status of final optics assembly on high power laser at 351nm laser is experimentally studied. We experimentally demonstrate 61 shots of 310mm × 310mm laser. The maximum laser energy flux is 5.5J/cm². The laser energy conversion efficiency is more than 72%. And the laser perforation efficiency across 800μm at 3000J is more than 96%. These results provide valuable information to improve final optics assembly performance research of high power laser.

The Laser MegaJoule (LMJ) is a 176-beam laser facility, located at the CEA CESTA near Bordeaux (France). It is designed to deliver about 1.4 MJ of energy to targets, for high energy density physics experiments, including fusion experiments.

A computational system, PARC has been developed and is under deployment to automate the laser setup process, and accurately predict laser energy, spatial and temporal shapes. PARC is based on MIRO computer simulation code. For each shot on LMJ, PARC determines the characteristics of the injection laser system required to achieve the desired main laser output and supplies post-shot data analysis and reporting.

The presentation compares all characteristics (energy, spatial and temporal shapes, spot size, synchronism, wavefront correction and alignment on target) after amplification and after frequency conversion with predicted results or results computed with PARC.

We designed and produced optical coatings for broad bandwidth high reflection (BBHR) of femtosecond (fs) pulses for high energy petawatt (PW) lasers. These BBHR coatings consist of TiO₂/SiO₂ and/or HfO₂/SiO₂ layer pairs formed by reactive E-beam evaporation with ion-assisted deposition in Sandia’s Large Optics Coating Facility. Specifications for the HR band and center wavelength of the coatings are for 45° angle of incidence (AOI), P polarization (Ppol), with use of the coatings at different AOIs and in humid or dry/vacuum environments providing corresponding different HR center wavelengths and spectral widths. These coatings must provide high laserinduced damage threshold (LIDT) to handle the PW fluences, and also low group delay dispersion (GDD) to reflect fs pulses without distortion of their temporal profiles. We present results of LIDT and GDD measurements on these coatings. The LIDT tests are at 45° or 65° AOI, Ppol in a dry environment with 100 fs laser pulses of 800 nm line center for BBHR coatings whose HR band line centers are near 800 nm. A GDD measurement for one of the BBHR coatings whose design HR center wavelength is near 900 nm shows reasonably low and smoothly varying GDD over the HR band. Our investigations include BBHR coatings designed for 45° AOI, Ppol with HR bands centered at 800 nm in dry or vacuum environments, and featuring three options: all TiO₂/SiO₂ layer pairs; all HfO₂/SiO₂ layer pairs; and TiO₂/SiO₂ inner layer pairs with 5 outer HfO₂/SiO₂ layer pairs. LIDT tests of these coatings with 100 fs, 800 nm line center pulses in their use environment show that replacing a few outer TiO₂ layers of TiO₂/SiO₂ BBHR coatings with HfO₂ leads to ~ 80% higher LIDT with only minor loss of HR bandwidth.