The future space X-ray astronomy imaging missions require very large collecting areas at still fine angular resolution and reasonable weight. The novel substrates for X-ray mirrors such as Silicon wafers and thin thermally formed glass enable wide applications of precise and very light weight (volume densities 2.3 to 2.5 gcm-3) optics. The recent status of novel technologies as well as developed test samples with emphasis on precise optical surfaces based on novel materials and their space applications is presented and discussed.
The future space X-ray astronomy imaging missions require very large collecting areas at still fine angular resolution and reasonable weight. The novel space Xray optics substrates such as Silicon wafers and thin thermally formed glass enable wide applications of precise and very light weight (volume densities 2.3 to 2.5 gcm-3) optics. The recent status of novel technologies as well as developed test samples with emphasis on precise optical surfaces based on novel materials and their space applications will be presented and discussed.
Space X-ray imaging telescopes have delivered unique observations that have been significantly contributing to many important discoveries of current astrophysics. For future telescopes with a larger collecting area and a better angular resolution, the limiting factor is their X-ray reflecting mirror array. Therefore, for a successful construction of future lightweight and highly reflecting X-ray mirrors, new cost-effective technologies and progressive materials are needed. Currently, the very promising materials are silicon foils which are commercially produced on a large scale. We focused on the plastic deformation of thin monocrystalline silicon foils, which was necessary for the precise thermal forming of the foils to 3D shapes. To achieve the plastic deformation, we applied forced slumping at temperatures from 1200 to 1400°C. The final shapes and the surface quality of the foils were measured using a Taylor Hobson contact profilometer and examined with an Atomic Forced Microscopy. We studied the effects of temperature, applied slumping force, heattreatment time, crystal orientation, and furnace atmosphere on the shape and surface quality of the formed foils.
In this work we have studied fundamental passive and active parameters of new family of erbium and ytterbium doped
zinc-silicate glasses with different doping concentration and ratio of erbium and ytterbium ions. Parameters as absorption
coefficient, saturation of absorption, emission wavelength, fluorescence lifetime and up-conversion spectra were
measured. The laser performance was studied in end-diode pumped configuration with hemispherical resonator. As an
excitation source a 30W fiber coupled 975 nm laser diode in pulsed regime was used. Laser action was achieved with
four different samples of zinc-silicate glasses on wavelengths ranging from 1540nm to 1570nm. The results were
compared with the properties of commercially available phosphate glasses and previous zinc-silicate glass which have
similar threshold energy corresponding to 3,3mJ and 3mJ respectively. Newly designed zinc-silicate glasses prepared
under improved conditions showed substantially better optical and laser properties in comparison with the previously
prepared samples.
We developed a non-contact method for in-situ monitoring of the thermal slumping of glass and silicone foils to optimize
this technology for the production of high quality mirrors for large aperture x-ray space telescopes. The telescope's
crucial part is a high throughput, heavily nested mirror array with the angular resolution better than 5 arcsec. Its
construction requires precise and light-weight segmented optics with surface micro-roughness on the order of 0.1 nm.
Promising materials are glass or silicon foils shaped by thermal forming. The desired parameters can be achieved only
through optimizing the slumping process. We monitored the slumping by taking the snapshots of the shapes every five
minutes at constant temperature and the final shapes we measured with the Taylor Hobson profilometer. The shapes were
parabolic and the deviations from a circle had the peak-to-valley values of 20-30 μm. The observed hot plastic
deformation of the foils was controlled by viscous flow. We calculated and plotted the relations between the middle part
deflection, viscosity, and heat-treatment time. These relations have been utilized for the development of a numerical
model enabling computer simulation. By the simulation, we verify the material's properties and generate new data for
the thorough optimization of the slumping process.
We report on recent progress with development of astronomical X-ray optics based on bent Si wafers. Recent efforts
with Si wafers have been focused on new forming technologies such as method of deposition of thin layers. The role of
substrates quality in performance of final mirror arrays, as required by large future space X-ray astronomy experiments
was also studied.
We report on the continuation of the development of test samples of astronomical x-ray optics based on thermally
formed glass foils and on bent Si wafers. Experiments with thermal glass forming have continued adding wider range of
evaluated and optimized parameters including viscosity and internal stress analyses, as well as investigation of mounting
influences. Experiments with Si wafers focused on their quality improvements such as flatness and thickness uniformity
in order to better meet the requirements of future X-ray astronomy projects applications, as well as on study of their
surface quality, defects analysis, and methods for its reproducible measurement.
We report on recent progress with development of astronomical X-ray optics based on thermally formed glass foils
and on bent Si wafers. Experiments with thermal glass forming have continued adding wider range of evaluated
and optimized parameters. Recent efforts with Si wafers have been focused on their quality improvements such
as flatness and thickness uniformity in order to better meet the requirements of future X-ray astronomy projects
applications, as well as on study of their surface quality, defects analysis, and methods for its reproducible measurement.
The role of substrates quality in performance of final mirror arrays, as required by large future space X-ray astronomy
experiments was also studied.
We report on recent progress with development of astronomical X-ray optics based on thermally formed glass foils
and on bent Si wafers. Experiments with thermal glass forming have continued adding wider range of evaluated
and optimized parameters. Recent efforts with Si wafers have been focused on their quality improvements such
as flatness and thickness uniformity in order to better meet the requirements of future X-ray astronomy projects
applications, as well as on study of their surface quality, defects analysis, and methods for its reproducible measurement.
The role of substrates quality in performance of final mirror arrays, as required by large future space X-ray astronomy
experiments was also studied. The problem of increasing size of Si wafers, required for some X-ray optics applications,
is also addressed. First results of irradiation tests of selected substrates are also reported and discussed.
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.
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 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).
To investigate the effect of divalent cations, we melted a set of sodium silicate baseline glasses with different concentrations of Ca2+, Mg2+, and Zn2+. We doped each of these basic glass matrices with several different amounts of Er3+ cations. These samples have been characterized in terms of absorption spectra, luminescence spectra, and experimental lifetime of the erbium metastable state. We also fabricated planar waveguides using Ag+/Na+ ion-exchange process. Characteristic parameters of the waveguides such as the number of modes, the refractive index change, the depth of the diffused region, and the propagation loses were measured. The mutual replacements of the divalent cations influenced the electron donor power (basicity) of oxygen atoms coordinating metal ions in glass. Measured optical spectra, lifetime values, and waveguiding parameters reflected the changes in glass basicity. To quantify the individual effects of Ca2+, Mg2+, and Zn2+, we calculated composition-property models based on polynomial functions with multiple variables. Correlation coefficients R2 varied from 0.991 to 1.000 indicating good linear correlations between the parameters and composition. The evaluation of glass component effects on the studied parameters enabled us quantify the chemical influence of the divalent cations. We discussed this influence using the optical basicity theory that predicts the variations of the electron donor power of oxygen atoms with glass composition. The knowledge of component effects is very useful for the effective formulation of new glass compositions. New Er glasses containing Zn2+ and/ or Mg2+ as divalent cations are promising materials for optical waveguide amplifiers.
The transition element (silver, copper and erbium) ions exchange fabrication and properties of the planar optical waveguides are reported for a variety of commercial and specially formulated optical glasses. The properties of the waveguides are discussed from the point of view of the stability of the oxidation state of the diffusing ions and the composition of the substrate glasses, taking into account the ratios of the bridging (BO) and non-bridging (NBO) oxygen atoms in the glass matrixes and the type of the fining agents used.
We present a study of fabrication and properties of planar optical waveguides fabricated by Ag+, Cu+, Cu2+ and Er3+ ion exchange in a variety of commercial as well as non-commercial optical glasses. The properties of the waveguides are discussed from the point of view of composition of the substrate glasses (taking into account the ratios of the bridging and non-bridging oxygen atoms in the glass matrixes and fining agents), luminescence and waveguiding properties as refractive index profiles and birefringence. The samples containing exclusively Cu+ exhibited very strong blue-green luminescence despite their low content of copper. The localized Er3+ doping into the glass wafers is presented for the first time.
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