As part of the LIL (Ligne d'Integration Laser) and LMJ (Laser Megajoule) projects, CEA/CESTA and SAGEM company have carried out an accurate metrology of the back focus length of filtering lenses. These measurements should enable us to make up for a lack of focus adjustment on the laser and to correctly position these lenses. Three different lenses have been characterized: • Lenses L1 and L2 with a back focus length of 10 m (aperture of F/16). Uncertainty is estimated at ±1,3 mm. • Lens L3 with a back focus length of 26 m (aperture of F/43). Uncertainty is estimated at ±5,3 mm. To achieve these measurements, 4 methods have been used: (1) Measurement of the curvature radius of each side on a Coordinate Measuring Machine and index homogeneity characterization before polishing. (2) Interferometric measurement with a reference spherical mirror. (3) Interferometric measurement using a lens side as a reference spherical mirror with a flat mirror. (4) Interferometric measurement by closing the cavity at the top of the lens back side. Uncertainty calculation has been done for each method.
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 mm2 with LIDT-3ns>25 J/cm2 have to be produced. Using a 5 m3 vacuum chamber and the 100 J/cm2 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 CEA: LIDT measurement and Raster-Scan on samples; reflectance mapping on CEA automatic photometer; reflected wavefront deformation with &nullset; 800 mm/1ω CEA interferometer.
SAGEM, within its REOSC high performance optics product line, has developed through the years a specific knowledge in large plano, spherical and aspherical optics for high energy or high power laser. This paper is aimed to illustrate the application of aspheric optics for such laser application with several examples of increasing optical surface complexity.
REOSC has supplied Indian Space Research Organization in 1998 and 1999 with two sets of eight lens assemblies to be used for the Ocean Color Monitor mission. First set will be launched on the Indian earth observation satellite IRS P4 during 1999. All lenses have a 20mm focal length and work with a very wide field of view angle. Each set of lenses covers the visible range using eight narrow spectral bands, one for each lens, distributed from 412nm to 865nm. The eight lenses of one set are matched for perfect registration: focal length better than +/- 0.01 percent, image format better than +/- 2 micrometers , distortion better than +/- 0.45 micrometers for each point of the field. In order to achieve these very tight requirements, REOSC has developed a specific spheroparabolic lens and particularly the process allowing to polish the parabolic surface with a very repetitive quality. A method has been settled to achieve the matching specifications of the lens assemblies by iterative correction of the optical design during the testing activities. The paper discusses the main points of these topics, reports this optical fabrication and testing challenge and presents the final obtained performances.
This paper reports the beginning of laser amplifier discs and spatial filtering lens polishing activities performed at REOSC for the Laser Megajoule project Ligne d'Intergation Laser prototype facility.
The corrective features of diffractive optics, as well as their ability to reduce costs, weight, size of conventional optical systems, show the great potentiality of these optics. In this field, the main application carried out by SFIM ODS is the chromatic aberration correction for high quality imaging systems particularly in the infrared range. In section II, Basic properties of the surface relief Diffractive Optical Element are presented. Then, section III-IV discuss about hybrid optics, optical design and complementary analysis. Finally we present design and experimental results in sections V-VI.