SESO has developed in the field of a R and T program of CNES a hollow cube corner in which there is no cement for bonding the three mirrors and with silicon, a good thermal conductivity material, both of which allows to guarantee a very good thermal stability particularly if the cube corner is enlighted by the sun on part of its surface. The complete assembly includes also the mechanical holder allowing to fix the cube corner on a baseplate without distorting it.
We will present the conceptual design, the technology used for assembling the three parts of the cube, simulations made on environmental behaviour, results achieved on a mock-up of the cube corner (wavefront distortion, angular accuracy, coating reflectivity, weight …).
High precision space optics, such as spectrometers, relay optics, and filters, require ultra stable, lightweight platforms. These equipped platforms have on one side to survive the launch loads, on the other side they have to maintain their stability also under the varying thermal loads occurring in space. Typically such platforms have their equipment (prisms, etalons, beam expanders, etc.) mounted by means of classical bonding, hydro-catalytic bonding or optical contacting. Therefore such an optical bench requires to provide an excellent flatness, minimal roughness and is usually made of the same material as the equipment it carries (glass, glass ceramics).
For space systems, mass is a big penalty, therefore such optical platforms are in most cases light weighted by means of machining features (i.e. pockets). Besides of being not extremely mass efficient, such pockets reduce the load carrying capability of the base material significantly.
The challenge for Oerlikon Space, in this context, was to develop, qualify and deliver such optical benches, providing a substantial mass reduction compared to actual light weighted systems, while maintaining most of the full load carrying capacity of the base material.
Additionally such a substrate can find an attractive application for mirror substrates. The results of the first development and of the first test results will be presented.
For the Pleiades space program, SESO has been awarded the contract (fully completed), for the manufacturing of the whole set of telescope mirrors (4 mirrors, 2 flight models). These works did also include the mechanical design, manufacturing and mounting of the attachment flexures between the mirrors and the telescope main structure. This presentation is focused on the different steps of lightweighting, polishing, integration and control of these mirrors as well as a presentation of the existing SESO facilities and capabilities to produce such kind of aspherical components/sub-assemblies.
RUAG Space, together with THALES SESO, initiated the development of light weighted sandwich structures
for optical applications, already some years ago. The results of the use of this type of structure applied for
optical benches and the first outlook for their use as mirror substrates were published in previous papers. This
paper is going to present the results of the polishing activities performed on a 650 mm diameter mirror
manufactured with Zerodur face sheets and a low density aluminum core. This substrate showed a mass
density of 15 kg/m2. The excellent optical quality achieved proves the suitability of this technology for several
applications, in particular for scanning mirrors for space and possibly for moveable mirror in ground based
With the emerging need for extremely high flatness under thermal loads (radius of curvature < 400km)
activities have been initiated to identify materials for the core of the substrate closer matching the extremely
low CTE offered by materials like Zerodur. The progresses made in this field are presented and an outlook for
future activities is provided.
High precision space optics requires ultra stable lightweight platforms, which have to survive the launch loads and to
maintain their stability under space environment. Such benches require a high planarity, small roughness and are usually made of the same material as the carried equipment. For space systems mass is a penalty, thus optical platforms are lightweighted by machining features. Besides of being not too mass efficient, this reduces significantly the load carrying capability of the base material. The challenge for us was to develop, qualify and deliver optical benches, providing a high mass reduction, while maintaining the load carrying capacity of the base material. Such an optical bench has been developed and built by Oerlikon Space and was equipped together with SESO with the high performing optical components for the flight model of the Aladin Mie Spectrometer for Astrium Toulouse. All tests
have proven the high strength and stability of the adopted concept.
Introduction of computer polishing machines has improved the flatness correction obtained on large optical components in different fields of activity (Astronomy, High Power Lasers, Space Activity, X-ray Mirrors for Synchrotron). It is now possible to produce off-axis aspheric mirrors with incidence angle greater than 20 degrees or aspheres with aperture number greater than F/1. To produce optics for Fusion by laser or large telescopes projects special machines or facilities have to be designed and installed. We will show the kind of studies, which are done in order to be able to produce these components as serial products and show some statistical results of flatness errors achieved on a production of 400 by 400 mm2 flat windows.
Optical contacting is a very interesting technology to realise stable assemblies.
We will describe the latest results that were achieved thanks to Silicate Bonding with different unusual materials as Silicon, Silicon Carbide and present some examples of complex assembly:
1. Double Fabry-Perot qualified for space application
2. Stabilised bench for ultra stables wavelength lock-up system.
As part of LMJ project (Laser Megajoule), CEA has built the LIL - Ligne d'Integration Laser - a LMJ prototype. This prototype uses full sized optics (400x400 mm2) with very tight specifications. SESO is one of the suppliers of optical components for this laser, among them filtering lenses - called L3 and L4 - used at 1053 nm (1ω), thin flat plates - continuous phase plates and debrishield - and thick windows, all used at 351 nm (3ω).
All these optics are in fused silica and combine good wavefront specifications, very low roughness and no or few surface quality defects.
Today, including spare parts, about 40 components have been produced.
The purpose of this paper is to describe the facilities for grinding, polishing and finishing these optics.
Computer Controlled Polishing robot for lenses
Double side polishing machine for flat optics
After a brief presentation of the specific metrology used, we give a detailed overview of the performances obtained on the produced components.
This work is related to the LIL - LMJ project directed by CEA, France.
PREUVE is the French federative program aimed at developing knowledge concerning the critical issues of EUV Lithography. The project supported by the French ministry of industry is one of the most important project in the field of nano-technologies in France. PREUVE is focused on different relevant aspects of the EUV lithography. Different kinds of EUV sources at 13.5nm for the purposes of lithography and metrology have been studied. Also reflective optics and multilayer coatings for the illuminating and the projection cameras have been realized. A complete development of EUV masks including substrates, multilayer coatings and reticules has been realized. Relevant metrologies for reflectivity measurements and defects detection have been developed. Finally the construction of an experimental exposure bench with high magnification (x10) and very high numerical aperture (0.32) has been pursued for process development. A summary of the results obtained in the frame of the project is presented hereafter.
Advanced Wolter X-ray microscope is developed to diagnose laser-produced plasmas and for the researching Inertial Confinement Fusion (ICF). The microscope is composed of two aspherical mirrors. We present X-ray Imaging Diagnostic and imaging studies we have performed with two kinds of X-ray source: an x-ray generator and a plasma laser x-ray source obtained with a power laser facility at 'Centre d'etudes de Limeil-Valenton,' France. A spatial resolution of better than 4 micrometer has been obtained in the 1 - 5 keV range over a field of 500 micrometer and for different magnifications varying from 15 to 40.
Last year we presented a paper about a mechanical bender in which we manufacture a complete structure holding the mirror and the actuator. Although very accurate this system is very expensive, so we have developed a new generation of mechanical benders in which the mirror itself is used as part of the structure.
We present a description of two types of bendable devices that have been manufactured and tested by SESO: bendable mirror with external bending mechanism and cooling, and long bimorphic bendable mirror with piezoelectric drive. A comparison chart of these devices will show the advantage of each solution.
Reflective optics operated at grazing angle of incidence has a good polarization transfer function and was preferred to focus or steer the X-ray beam on the ESRF beamline ID12A which is dedicated to X-ray dichroism. The present paper reports on the design of a double mirror device (VF-2M) that is located downstream with respect to the monochromator and can refocus the X-ray beam vertically very near the sample location. This system combines two identical mirrors (L equals 600 mm; W equals 40 mm; T equals 12 mm) made of bulk CVD-SiC which were polished to a very precise cylindrical shape: when no bending forces are applied, each mirror has a concave curvature radius of 1 km with a slope error
The new properties of third-generation synchrotron radiation beams call for corresponding progress in instrumentation technology. This is particularly true for hard x-ray mirrors, for which new technologies have been implemented to meet outstanding requirements. The transfer of experience from other fields such as high-energy lasers and astronomy has been of major importance in the realization of new designs. The European Synchrotron Radiation Facility, the first third-generation hard x-ray source in Europe, has stimulated R&D programs of four European companies in the field of hard x-ray mirrors. This paper presents the major achievements of these companies.