In this presentation we share how the development of step-and-repeat DTL technology is addressing the growing need for periodic patterning in large-area device fabrication for display, AR/VR, and other photonic applications with low-cost, high-throughput (+40wph), high-resolution (UV, DUV) capabilities.
Like projection lithography, non-contact, optical patterning is very repeatable and with a particle controlled mini-environment, robust to defectivity. Unlike projection, the DTL image is not limited to a small depth of focus (DOF). High resolution patterning is reliable over non-planar substrates and topography (300-400um), which is especially useful in applications where substrates are thick or so large that flatness is difficult to control.
Other production–centric features include fully automated wafer and mask handling and high wafer throughput (+40wph). This technology shares the same material and process solutions that have been successfully used for semiconductor lithography for decades.
Currently for the European Space Agency (ESA) ATHENA [1,2] mission Silicon Pore Optic (SPO) [3-8] Mirror Modules (MM) with a focal length of f = 12 m, are being developed and tested. The SPO MMs are also the baseline optic for the NASA medium explorer high-resolution spectroscopy mission Arcus [9-10] with f = 12 m that is currently undergoing a phase A study. SPOs are currently being tested at both the PTB laboratory of the BESSY synchrotron facility in Berlin using an X-ray pencil beam and the PANTER X-ray test facility in Neuried of the Max-Planck-Institut für extraterrestrische Physik, Garching using a long vacuum beamline (distance source to optic ~120 m). The different types of measurements performed at PANTER to characterise the ATHENA and Arcus optics will be discussed. This will be done on the level of an X-ray optical unit (XOU) composed of both a primary and secondary High Performance Optic (HPO) stack, a mirror module (MM) composed of two XOUs, small (<4 MMs) and large (< 25 MM) petals, and the complete integrated optic Athena (700-1000 MMs) and Arcus (4 petals each with 38 MMs). The main set of tests that are currently done at PANTER make full use the possibility to fully-illuminate single XOUs, MMs, and petals to determine their optical characteristics such as the half energy width of the point spread function as well as the effective area and the vignetting function at different energies. To ensure that the measurements, that are required to demonstrate the performance of ATHENA, are possible, a description of recent and upcoming upgrades to the PANTER X-ray test facility will be given. Finally, a status update on the progress on designing the new facility to be used to test and calibrate the complete ATHENA mirror will be presented.
Within the ATHENA optics technology plan, activities are on-going for demonstrating the feasibility of the mirror module integration. Each mirror module has to be accurately attached to the mirror structure support by means of three isostatic mounts ensuring minimal distortion under environmental loads. This work reports on the status of one of the two parallel activities initiated by ESA to address this demanding task. In this study awarded to the industrial consortium, the integration relies on optical metrology and direct X-ray alignment. For the first or “indirect” method the X-ray alignment results are accurately referenced, by means of a laser tracking system, to optical fiducial targets mounted on the mirror modules and finally linked to the mirror structure coordinate system. With the second or “direct” method the alignment is monitored in the X-ray domain, providing figures of merit directly comparable to the final performance. The paper updates on the laser tracking characterization results of 2 mirror modules, performed at PTB’s X-ray Parallel Beam Facility (XPBF 2.0) at BESSY II. The same 2 mirror modules have then been co-aligned and integrated in a technology demonstrator, with performance verified in full illumination at Panter. The paper provides an overview of the results obtained from the technology development activities.
Within the ATHENA optics technology plan, activities are on-going for demonstrating the feasibility of the mirror module Assembly Integration and Testing (AIT). Each mirror module has to be accurately attached to the mirror structure by means of three isostatic mounts ensuring minimal distortion under environmental loads. This work reports on the status of one of the two parallel activities initiated by ESA to address this demanding task. In this study awarded to the industrial consortium, the integration relies on opto-mechanical metrology and direct X-ray alignment. For the first or “indirect” method the X-ray alignment results are accurately referenced, by means of a laser tracking system, to optical fiducial targets mounted on the mirror modules and finally linked to the mirror structure coordinate system. With the second or “direct” method the alignment is monitored in the X-ray domain, providing figures of merit directly comparable to the final performance. The integration being designed and here presented, foresees combining the indirect method to the X-ray direct method. The characterization of the single mirror modules is planned at PTB’s X-ray Parallel Beam Facility (XPBF 2.0) at BESSY II, and the integration and testing campaign at Panter. It is foreseen to integrate and test a demonstrator with two real mirror modules manufactured by cosine.
KEYWORDS: Space telescopes, Telescopes, Temperature metrology, Mirrors, Space mirrors, Absorption, Thermography, Manufacturing, Optical design, Interfaces
RUAG Space developed, manufactured and demonstrated an afocal mirror telescope for space applications. The
telescope is part of a Laser Communication Terminal (LCT) for GEO and LEO satellites. The design is off-axis and free
of central obscuration. Optical interfaces are provided by pupils outside the telescope towards space (ø=135 mm) and
towards the payload (ø=12.5 mm). The magnification is Γ=-10.8. The main characteristics are a WFE of ≤35nm,
transmission <96%, low extinction ratio of linear and circular polarization, low stray light and low mass. The
performance stability was demonstrated under various environments including vibrations, shock and thermal-vacuum up
to 55°C. These properties enable a broad use, not limited to space. The layout is composed of four mirrors (Zerodur and
Fused Silica) integrated in a nearly zero expansion Carbon Fibre (CFRP) structure. A detailed characterisation and
advanced understanding of the CFRP represents a main achievement. The water absorption of CFRP in air causes elastic
distortions of the structure until saturation. Certain optical performances are affected by this phenomenon which has to
be considered when testing the system in thermal-vacuum environment. These effects were characterised and precompensated
during integration in order to tailor the performance to the in-orbit conditions. The stability of the
performances confirmed the selection of the CFRP as nearly-zero CTE material. Combined effects of moisture release
and thermo-elastic distortions under thermal-vacuum loads were detected. The optical performances verification was
then consequently and successfully tailored in order to distinguish these effects and prove the telescope stability under
thermal-vacuum environment.
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