As part of the LMJ (Laser Megajoule) program, CEA is building the LIL laser with full size optics and LMJ requirements. SAGEM has been selected as the supplier of large optical components and coatings with very high laser-induced damage threshold. Including spare parts, about 100 mirrors 610*430 mm(2) with LIDT-3ns > 25 J/cm(2) have to be produced.Using a 5 m(3) vacuum chamber and the much less than 100 J/cm(2) much greater than mirror coating process developed at CEA-LETI, with Hafnium. and SiO2 materials, we are now typically in a serial production phase. To date, about thirty mirrors have been delivered. This paper focuses on the acceptance tests performed after coating, at Sagem then CEALIDT measurement and Raster-Scan on samplesReflectance mapping on CEA automatic photometerReflected wavefront deformation with empty set 800 mm /1omega CEA interferometer.

The purpose of this paper is to determine the effect induced by the nodular defects in optical thin films under laser irradiation. A strong correlation between the size distribution of defects in optical thin films. The deposition parameters and the laser damage threshold is found. With this approach of the defects in thin films, it confirms that the size of a nodular defect is a critical parameter, while the density of the defects is not. The observations of damaged ares, performed by Scanning Electron MIcroscope (SEM), show that of the smallest ejected nodular defects associated with damaged zones, correspond to a critical mean size around 4 micrometers . A mechanical approach is also used to understand the role of the nodular defects under a mechanical solicitation. During the mechanical experiments it appears that depending on the nodular defects sizes, the initiation of cracking was more or less delayed. From the mechanical experiments, a critical size of about 4 micrometers is deduced. Besides, the analysis of these two different experiments points out that the laser damage induced by nodular defects is strongly related to mechanical fracture parameters.

Large components are needed to build up the Laser Megajoule which belongs to the future generation of fusion laser. It is essential to determine the laser damage threshold of full-size components with a large-size laser beam, and to compare this value to the threshold obtained on small samples with a small gaussian laser beam. So, we have, in the first place, tested some small samples from the same coating run on REOSC, CEA and LLNL facilities and, in a second series of experiments, we have tested three full-size optical components on the LLNL beamlet laser. Two types of optical components have been tested on the beamlet: - one polarizer: 710 X 400 nm; - two HfO2/SiO2 mirrors, from the same coating run: 620 X 440 mm. Before beamlet irradiation these components have been continued at 10 ns on the LLNL Plato facility. Concerning the mirrors, two different conditioning procedures have been applied: - on the first mirror a 5-step conditioning procedure; - on the second mirror a 2-step conditioning procedure. Then, each mirror has undergone the same test on the beamlet. In this paper we report the result obtained on the polarizer and the mirrors after beamlet irradiation.

Large components typically 620 mm x 440 mm are needed to build up the LMJ (Laser Megajoule) which belongs to the future generation of the fusion laser. Today the laboratory laser damage facilities allow to test small samples : generally witnesses with 50 am in diameter. However, more of the test procedures are manually and small areas are examined. It means that usually just 20 and 50 sites are tested with a small Gaussian beam ( about 2 mm at 1/e(2)). Therefore, it is essential to verify if the large components needed for the fusion laser have the threshold above the requirements (LIDT > 25 J/cm(2)). It is also important to determine which law exits between the threshold of the witnesses sample and the threshold of the final components. In this paper, these problems are addressed in using the most powerful pulsed Nd:YAG laser in France (Phebus). With this particular facility it becomes possible to test full scale optics on a few sites (typically 10) with a beam size diameter of 6 cm. Except the test on the real system, these kinds of experiments allow to observe the large beam damage morphologies. A study is at the beginning to try to find the scale law which linked the results obtained on the small witnesses with various methods. It also should lead to a procedure to qualify the full scale optics during the production time.

Accurate characterization of losses in optical multilayers remains critical for laser damage investigation. In particular, due to time deposition and shift of deposition parameters, materials within multilayers have different intrinsic properties according to their vertical location within the stack. For this reason, different extinction coefficients can be found for materials in single layer forms and materials confined in multilayers. Therefore a non- destructive probe is required that should permit to characterize separately each interface or each bulk of a multilayer. This probe is offered by guided wave and photothermal techniques that we present in this paper. Our technique allows us to measure loss anomalies in multilayer waveguides by recording an attenuation coefficient for each propagation mode, as well as a temperature distribution perpendicular to the mode direction. The results are analyzed to determine dissipate properties versus z-location within the stacks. At this step an attempt is made to correlate damage with loss anomalies.

The manufacture of modern optical components requires the use of high performance interferometers, usually based on phase-shifting techniques. However, there is currently no commercial phase-shifting interferometer having the capacity to measure large parts, such as those found in Inertial Confinement Fusion Lasers (NIF and Mega-Joule), and other large systems. Standard interferometers lack the simultaneous qualities of accuracy and spatial resolution required for the measurement of such components. Indeed, it has been shown that surface ripples with wavelengths of around 1 to 10 millimeters are extremely dangerous for large ICF optics, even at low amplitude, because of the process of non-linear ripple amplification present in high power laser systems. In order to circumvent the restrictions on size and performance of standard interferometers, we have designed and built a scanning interferometer, using a standard diameter phase shifting interferometer. A PC computer is used to control the measurement process, acquire the interferograms and stitch the measurements together to produce the original large surface. The measurement sequence is completely automated. The advantages ofthis technique are low cost, small size, and no loss ofspatial resolution. One system has been in actual use for the characterization of large size mirrors (approx. 400 x 600 mm) since december 1994. In this presentation, we shall look over the design of the system, produce actual measurements, and discuss the technical implications of the stitching process in relation to specifications such as those currently being derived for ICF large components. This work is supported by CEA/CEL-V, as part of the Laser MegaJoule Program.

One of the concerns with the megajoule laser design is the laser-induced damage threshold of the transport mirrors. Earlier studies have shown that the main constraint on the laser damage threshold comes from nodules at the mirror surface. It is therefore important to restrict the number of such nodules. SFIM-ODS, in close collaboration with CEL-V, has initiated a special study to characterize these nodules as precisely as possible. The objective of the study is twofold: (1) to determine the origin of the nodules and subsequently to adapt the mirror fabrication process in order to limit their formation, (2) to analyze their shapes and dimensions in order to ascertain which nodules are critical for laser-induced damage. To understand the origin of the nodules and their effect on the laser damage threshold, the mirrors are characterized using various methods: (1) absorption and scatter mapping: does the presence of nodules result in specific absorption patterns, (2) surface analysis by atomic force microscopy: to characterize nodule shape and dimensions, (3) focused ion beam cutting of nodules: to locate the seed initiating the nodule and to characterize the seed shape and composition, (4) laser damage threshold measurements: to determine the laser damage threshold of them mirror and study the behavior of nodules under laser irradiation depending on their dimensions and shape.

The French Megajoule Project requires polarizers with high laser-induced damage thresholds. Such polarizers must be deposited on silica substrates, which are commonly prone to stress leading to early failure. Better stress control in the films require an optimization of the stack design as well as the deposition parameters. The thermal e-beam technique is used. We present the spectral behavior of such 1.03 micrometers polarizers in air and under vacuum at the Brewster incidence angle of 55 degrees 4 along with the damage test results.

The Phebus Neodymium glass Laser system located at Centre d'Etudes de Limeil Valenton (CEL-V) is the most powerful in Europe (20 Id, 1 ns at = 1053nm and up to 8 U, 1 ns at = 351 nm). A major concern in the design of this system was the damage thresholds of the 1 meter diameter turning mirrors and of the large polarizers (0.3 m2). MATRA DEFENSE S .A. , in a joint effort with CEL-V, using the well known reactive e-beam process, has investigated and produced a new generation of efficient ZrO/SiO and HfO/SiO high reflective and polarizing coatings, leading to very high laser-conditioned damage thresholds. In addition to good flatness figures (t/4 to ?i /10 at He-Ne wavelength), excellent roughness values (5-10 A RMS) and excellent spectral characteristics, laser-conditioned damage thresholds were in the range of 25-30 J/cm2 and 12- 15 J/cm2 respectively for mirrors and polarizers at 1 .064 m wavelength for a 3 ns pulse. Such performances are respectively 2 and 6 times higher than those of same components in the Ti02/5i02 conventional design. Laser-conditioning effect, enhancing the damage threshold by at least a factor of 2, was observed as a durable improvement