Abstract
Reactively driven low-energy ion beam machining is a widely used finishing technique for optical aluminium surfaces. Direct RIBE machining with oxygen or nitrogen process gas permits figure error correction of diversely shaped aluminium optics while preserving the initial roughness up to 1 µm etching depth. Those optical surfaces are appropriate for applications in the infrared spectral range. For increasing demands on optical surfaces for short - wavelength applications in the visible and ultraviolet spectral range ion beam polishing techniques with the aid of a sacrificial layer are a promising process route. Turning marks situated in the high-to –mid spatial frequency range are remarkably reduced while preserving the initial microroughness resulting in an enhancement of the full range roughness.
Highlights
For increasing demands on high-performance optical systems, scattering effects resulting from surface errors are necessary to reduce.Technical aluminium alloy materials as Al6061 or Al905 are common mirror construction materials
For fabrication of optical aluminium surfaces conforming to the requirements in the infrared (IR) spectral range, usually single-point diamond turning (SPDT) is used [1, 2]
The surface errors to be corrected are specified by the spatial frequency range they emerge [4, 5]
Summary
For increasing demands on high-performance optical systems, scattering effects resulting from surface errors are necessary to reduce. For fabrication of optical aluminium surfaces conforming to the requirements in the infrared (IR) spectral range, usually single-point diamond turning (SPDT) is used [1, 2]. The demands on optical surface quality for applications in the short-wavelength visible (VIS) and ultraviolet (UV) spectral range increase immensely. The surface errors to be corrected are specified by the spatial frequency range they emerge [4, 5]. Depending on the lateral dimension, the surface errors are divided into low-spatial frequency (LSF), mid-spatial frequency (MSF) and high-spatial frequency (HSF) errors. Turning marks are typical feature types situated in the mid - to - high spatial frequency range of waviness and roughness (Fig. 1). Ion beam technologies driven by reactive process control are a promising process route to improve the optical performance since these slow surface machining techniques offer a high degree of precision
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