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We investigated the morphology and mechanism of laser-induced damage in the ablation cutting of thin glass sheets with picosecond laser. Two kinds of damage morphologies observed on the cross-section of the cut channel, are caused by high-density free-electrons and the temperature accumulation, respectively. Notches and micro-cracks can be observed on the top surface of the sample near the cut edge. The surface micro-cracks were related to high energy free-electrons and also the heat-affected zone. Heat-affected-zone and visible-cracks free conditions of glass cutting were achieved by controlling the repetition rate and spatial overlap of laser pulses.

The Slumped Glass Optics technology, developed at INAF/OAB since a few years, is becoming a competitive solution for the realization of the future X-ray telescopes with a very large collecting area, e.g. the approved Athena, with more than 2 m2 effective area at 1 keV and with a high angular resolution (5'' HEW). The developed technique is based on modular elements, named X-ray Optical Units (XOUs), made of several layers of thin foils of glass, previously formed by direct hot slumping in cylindrical configuration and then stacked in a Wolter-I configuration, through interfacing ribs. The latest advancements in the production of thin glass substrates may allow a great simplification of this process, avoiding the preforming step via hot slumping. In fact, the strength and the flexibility of glass foils with thickness lower than 0.1 mm allow their bending up to very small radius of curvature without breaking. In this paper we provide an update of the project development, reporting on the last results achieved. In particular, we present the results obtained on several prototypes that have been assembled with different integration approaches.

Reosc has been working on thin glass shells for many years and was recently selected by ESO for the production of the E-ELT M4 mirror thin glass shells. Previously Reosc also produced the aspheric thin shell for the VLT-M2 AO Facility. Based on this experience we will discuss how off axis thin glass shells can be made for the next generation AO systems like the GMT one.

Previously used mirror technologies are not able to fulfil the requirements of future X-ray telescopes due to challenging requests from the scientific community. Consequently new technical approaches for X-ray mirror production are under development. In Europe the technical baseline for the planned X-ray observatory ATHENA is the radical new approach of silicon pore optics. NASA´s recently launched NuSTAR mission uses segmented mirrors shells made from thin bended glasses, successfully demonstrating the feasibility of the glass forming technology for X-ray mirrors. For risk mitigation also in Europe the hot slumping of thin glasses is being developed as an alternative technology for lightweight X-ray telescopes. The high precision mirror manufacturing requires challenging technical developments; several design trades and trend-setting decisions need to be made and are discussed within this paper. Some new technical and economic aspects of the intended glass mirror serial production are also studied within the recently started interdisciplinary project INTRAAST, an acronym for "industry transfer of astronomical mirror technologies". The goal of the project, embedded in a cooperation of the Max-Planck-Institute for extraterrestrial Physics and the University of Applied Sciences Aschaffenburg, is to master the challenge of producing thin mirror shells for future X-ray telescopes. As a first project task the development of low stress coatings for thin glass mirror substrates have been started, the corresponding technical approach and first results are presented.

Recent advancements in thin glass materials allowed the development and the mass production of very thin glass foils, like e.g. the Willow glass (thickness of 0.1-0.2 mm) produced by Corning or AF32 produced by Schott (thickness down to 0.055 mm). The thickness, strength and flexibility of these glass foils allow bending them up to very small radius of curvature without breaks. This feature, together with the very low micro-roughness, makes this kind of materials ideal candidates for pursuing a cold replication approach for cost-effective and fast making of grazing incidence astronomical optics. Starting from the very thin flat glass sheets, the process under development foresees to bond them onto the supporting structure while they are wrapped around reference mandrels. The assembly concept, based on the use of Wolter-I counter-form moulds, is also based on the use of reinforcing ribs that connect pairs of consecutive foils in the final assembly. The ribs do not only play the role of mechanical connectors, they keep the shape and increase the structural stiffness. Indeed, the ribs constrain the foil profile to the correct shape during the bonding, damping the low-frequency residuals with respect to the Wolter I configuration. This approach is particularly interesting because of their low weight and cost. They could e.g be used for the production of high throughput optics as those needed for the Chines XTP mission, in which the requirements on the angular resolution are not too tight. In fact, a Half Energy Width in the range of 20-60 arcsec is compatible with the expected residual error due to the spring back of the glass sheets. In this paper we provide an overview of the project, the expected performances and present the first preliminary results.

The cold glass-slumping technique is a low cost processing developed at INAF-Osservatorio Astronomico di Brera for the manufacturing of mirrors for Cherenkov telescopes. This technology is based on the shaping of thin glass foils by means of bending at room temperature. The glass foils are thus assembled into a sandwich structure for retaining the imposed shape by the use of a honeycomb core. The mirrors so manufactured employ commercial off-the-shelf materials thus allowing a competitive cost and production time. They show very low weight, rigidity and environmental robustness. In this contribution we give an overview on the most recent results achieved from the adoption of the cold-shaping technology to different projects of Cherenkov telescopes. We show the variety of optical shapes implemented ranging from those spherical with long radius of curvature up to the most curved free form ones.

Future X-ray telescopes aim for large effective area within the given mass limits of the launcher. A promising method is the hot shaping of thin glass sheets via a thermal slumping process. This paper presents the status and progress of the indirect glass slumping technology developed at the Max-Planck-Institut for extraterrestrial Physics (MPE). Recent developments in our research include the use of the mould material Cesic under vacuum, as well as the fabrication of a high-precision slumping mould, which meets the requirements of large, high angular resolution missions like ATHENA. We describe the way forward to optimise the slumping process on these materials, the force-free integration concept and its progress, as well as the first test on reflective coating application.

High-resolution, high throughput optics for x-ray astronomy entails fabrication of well-formed mirror segments and their integration with arc-second precision. In this paper, we address issues of aligning and bonding thin glass mirrors with negligible additional distortion. Stability of the bonded mirrors and the curing of epoxy used in bonding them were tested extensively. We present results from tests of bonding mirrors onto experimental modules, and on the stability of the bonded mirrors tested in x-ray. These results demonstrate the fundamental validity of the methods used in integrating mirrors into telescope module, and reveal the areas for further investigation. The alignment and integration methods are applicable to the astronomical mission concept such as STAR-X, the Survey and Time-domain Astronomical Research Explorer.

The demand for larger collecting areas in X-ray telescopes within the mass limits of the launcher creates the need for light-weight mirror materials. At our institute we develop the technology of indirect thermal slumping of thin glass sheets to manufacture light mirror segments. A crucial part of the development is the measurement of the glass surface, shape and thickness profile in order to evaluate the quality of the reproduction method. We describe the measurement set-up, the analysis method of the surface profile and the evaluation of thickness variations in the glass, as well as their influence on the final glass sheets.

Lightweight, high-resolution, high throughput optics for x-ray astronomy requires fabrication and integration of thin mirrors segments with arc-second precision. In this paper, we present results on our effort leading to the most recent two test modules achieving the intermediate goal of 10 arc-second resolution. We will address issues of coating and bonding thin glass mirrors with negligible distortion. Annealing of sputtered high-density metallic films was found to be sufficiently accurate. We will present result from tests of bonding mirrors onto experimental strongbacks, as well as the sensitivity on bonding procedure, bond parameters and environment.

Future X-ray telescopes need to combine large collecting area with good angular resolution. In order to achieve these aims within the mass limit, light-weight materials are needed for mirror production. We are developing a technology based on indirect hot slumping of thin glass segments; this method enables the production of the parabolic and hyperbolic part of the Wolter type I mirrors in one piece. Currently we use a combination of a porous ceramic for the slumping mould and the glass type D263 for the mirror material. In this study we use glasses that have been polished on one side to remove thickness variations in the glass, in order to investigate their influence on the results. We describe the experimental set-up, the slumping process and the metrology methods. Finally we present the results of an X-ray test of several integrated glass sheets, and give an outlook on future activities.

The International X-ray Observatory (IXO) is a joint mission concept studied by the ESA, NASA, and JAXA space agencies. The main goal of the mission design is to achieve a large effective area (>2.5m2 at 1 keV) and a good angular resolution (5 arcsec HEW at 1 keV) at the same time. The Brera Astronomical Observatory - INAF (Italy), under the support of ESA, is developing a method for the realization of the X-Ray Optical Units, based on the use of slumped thin glass segments to form densely packed modules in a Wolter type I optical configuration. In order to reach the very challenging integration requirements, it has been developed an innovative assembly approach for aligning and mounting the IXO mirror segments. The method is based on the use of an integration mould for each foil. In particular the glass segment is forced to adhere to the integration mould in order to maintain the optimal figure without deformations until the integration of the foil in the stack is completed. In this way an active correction for major existing figure errors after slumping is also achieved. Moreover reinforcing ribs are used in order to connect the facets to each-other and to realize a robust monolithic stack of plates. In this paper we present the design, the development and the validation status of a special Integration Machine (IMA) that has been specifically developed to allow the integration of the Plate Pairs into prototypal X-Ray Optical Unit stacks.

Effective area requirements for the large X-ray mirror of the International X-ray Observatory (IXO) are about 3 m2 at 1keV, 0.65 m2 at 6 keV and 150 cm2 at 30 keV. Because of its large dimension, the telescope cannot be realized as a monolithic structure but rather it requires the integration and assembly in the telescope optical bench of a number of basic module units, called X-ray Optical Unit (XOU). We are currently studying a method for the production of these basic units that is based on the slumping technology for the production of thin glass segmented mirrors. It foresees the implementation of a stacking integration concept based on the use of reinforcing ribs connecting the glass segments in order to create very stiff structures. This paper reports on the last design of the single optical module and describe the results of FEM analyses that show how it is possible to use an innovative approach to the integration of the slumped glass foils.

The next large x-ray astrophysics mission launched will likely include soft x-ray spectroscopy as a primary capability. A requirement to fulfill the science goals of such a mission is a large-area x-ray telescope focusing sufficient x-ray flux to perform high-resolution spectroscopy with reasonable observing times. The IXO soft x-ray telescope effort in the US is focused on a tightly nested, thin glass, segmented mirror design. Fabrication of the glass segments with the required surface accuracy is a fundamental challenge; equally challenging will be the alignment of the ~7000 secondary mirror segments with their corresponding primary mirrors, and co-alignment of the mirror pairs. We have developed a system to perform this alignment using a combination of a coordinate measuring machine (CMM) and a double-pass Hartmann test alignment system. We discuss the technique, its ability to correct low-order mirror errors, and results of a recent pair alignment including progress toward the required alignment accuracy of < 2 arcseconds. We then look forward toward its scalability to the task of building the IXO telescope.

As NASA's next major space X-ray observatory, the Constellation-X mission (Bookbinder et al. 2008) requires mirror assemblies with unprecedented characteristics that cannot be provided by existing optical technologies. In the past several years, the project has supported a vigorous mirror technology development program. This program includes the fabrication of lightweight mirror segments by slumping commercially available thin glass sheets, the support and mounting of these thin mirror segments for accurate metrology, the mounting and attachment of these mirror segments for the purpose of X-ray tests, and development of methods for aligning and integrating these mirror segments into mirror assemblies. This paper describes our efforts and developments in these areas.

The precisely shaped glass sheets and Si wafers are generally considered as the most promising substrates for future large space astronomical X-ray telescopes. Both approaches have demonstrated promising results obtained in the course of last years. In this contribution, we report on continued systematic efforts and analysis in precise shaping of thin glass sheets as well as Si wafers. New results will be briefly presented and discussed. For Si wafers, recent efforts focus also on improving the intrinsic quality of the slices to better meet the high requirements of future space projects.

We present the concepts behind current alignment and integration techniques for testing a Constellation-X primary-secondary mirror segment pair in an x-ray beam line test. We examine the effects of a passive mount on thin glass x-ray mirror segments, and the issues of mount shape and environment on alignment. We also investigate how bonding and transfer to a permanent housing affects the quality of the final image, comparing predicted results to a full x-ray test on a primary secondary pair.

The thermally formed thin glass foils and optically shaped Si wafers are considered to belong to the most promising technologies for future large space X-ray telescopes. We present and discuss the recent progress in these technologies, as well as properties of test mirrors produced and tested. For both technologies, both flat and curved samples have been produced and tested. The achieved profile accuracy is of order of 1 micrometer or better, while the bending technologies maintain the intrinsic fine surface microroughness of substrates (better than 0.5 nm for glass and around 0.1 nm for Si wafers).

The accurate detection of minute amounts of chemical and biological substances has been a major goal in bioanalytical technology throughout the twentieth century. Fluorescence dye labeling detection remains the effective analysis method, but it modifies the surroundings of molecules and lowering the precision of detection. An alternative label free detecting tool with little disturbance of target molecules is highly desired. Theoretical calculations and experiments have demonstrated that many biomolecules have intrinsic resonance due to vibration or rotation level transitions, allowing terahertz (THz)-probing technique as a potential tool for the label-free and noninvasive detection of biomolecules. In this paper, we first ever combined the THz optoelectronic technique with biochip technology to realize THz biosensing. By transferring the edge-coupled photonic transmitter into a thin glass substrate and by integrating with a polyethylene based biochip channel, near field THz detection of the biomolecules is demonstrated. By directly acquiring the absorption micro-spectrum in the THz range, different boiomecules can then be identified according to their THz fingerprints. For preliminary studies, the capability to identity different illicit drug powders is successfully demonstrated. This novel biochip sensing system has the advantages including label-free detection, high selectivity, high sensitivity, ease for sample preparation, and ease to parallel integrate with other biochip functionality modules. Our demonstrated detection capability allows specifying various illicit drug powders with weight of nano-gram, which also enables rapid identification with minute amounts of other important molecules including DNA, biochemical agents in terrorism warfare, explosives, viruses, and toxics.

The future large space X-ray telescopes in study (such as the ESAs XEUS) require novel approaches and innovative lightweight technologies. Although there are several alternative possibilities, in general the shaped thin glass foils and shaped Si wafers are considered to belong to the most promising ones. We present and discuss the recent progress in these technologies, as well as properties of test mirrors produced and tested. For both technologies, both flat and curved samples have been produced and tested. The achieved profile accuracy is of order of 1 micrometer or better, while the bending technologies maintain the intrinsic fine surface microroughness of substrates (better than 0.5 nm).

The future X-ray astrophysics space missions require very light-weight but large and precise X-ray mirrors shells. Clearly, developments of innovative techniques and approaches are necessary. We discuss the possible alternative techniques with focus on the technologies and experience available in the Czech Republic. They include light ceramics replication by plasma spraying as well as by CVD and PVD technologies, SiC, thin glass technology, improved electroforming, glossy carbon, as well as glossy metals.

We present an overview of our recent progress toward the development of segmented X-ray mirrors for the Constellation-X mission. Our reference design incorporates thin glass reflector substrates, with axially curved X-ray reflecting surfaces applied via epoxy replication. Alignment is accomplished via a precision structure incorporating ultraprecise etched Si alignment microstructures (as described in associated papers). Recent efforts have been devoted to demonstrating that the figure of prototype small segments and the alignment process will allow us to meet the 15" half-power diameter angular resolution requirement. We discuss the status of this, of our efforts to fabricate meter-class segments, and of the developments of supporting metrological techniques. We summarize our plans for a laboratory demonstration of a prototype mirror meeting the Constellation-X angular resolution and weight requirements.

This illumination system is one component of a holographic camera, which is part of a multi-disciplinary, multi-national project (funded by the European Commission MAST III initiative) to use holography for the in situ recording and subsequent analysis of holograms of marine organisms and particles. Laboratory experiments have shown that the best results for off-axis recording are obtained using side illumination. Our design goal has been to provide even side illumination throughout the recording volume. This illumination system, the lightrod, is based on a cylinder made from a transparent material containing a series of partial reflectors inclined and spaced along its length. An unexpanded laser beam is fed into the cylinder along its axis. Each reflector diverts a fraction of the beam into the recording volume. Two versions of the lightrod have been designed and built. In one version, the cylinder uses solid Perspex spacers with a small air gap in between; in the other, the spacers are hollow with thin glass windows in between. Both lightrod designs are discussed together with an analysis of the illumination profile, and their practical implementation is outlined. Both lightrod prototypes have been tested in an observation tank. Results from these tests are presented.