Rehau (France)

High end applications in infrared may benefit from infrared colorimetry. Actual systems are designed using filter wheel, gratings or dichroic components. Those systems are bulky, do not allow real-time acquisition and are sensitive to stray light. Sagem & Reosc recently developed technologies to pixelate infrared coating filters at detector level. It allows designing very compact systems, easy to cool down and to significantly reduce ghost images. Optical systems are simplified and can achieve fast acquisition of multi-spectral video. Numerical simulations have been performed in order to quantify the pattern shape influence on the optical performances at the microscopic scale. The etching processes of multilayer stacks have been developed. Finally, prototypes have been manufactured and tested. This technology opens up new perspectives in the field of infrared filtering.

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.

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.