Renate Fechner

Ion beam and plasma jet etching for optical component fabrication

Ion beam figuring (IBF) using inert gas (e.g. Ar) and (Reactive) ion beam etching [(R)IBE] gain growing interest in precision optical surface processing, RIBE mainly for proportional transfer of 3D-resist masks structures in hard optical materials and IBF for finishing and nanometer precision surface figuring in high performance optics technology. Ion beam and plasma jet etching techniques related to different optical surface figuring requirements have been developed at IOM during the last decade. Some of these techniques have been proven to be mature for application in industrial production. The developmental work include material related process tuning with respect to enhance the processing speed and to improve surface roughness and waviness, further various processing algorithms related to different surface figure requirements and processing related equipment modification. Plasma jet assisted chemical etching is under development with respect to efficient machining techniques for precision asphere fabrication. The paper gives an overview of precision engineering techniques for optical surface processing focusing on the status of ion beam and plasma techniques. The status of the proportional transfer of 3D micro-optical resist structures (e.g. micro-lens arrays, blazed fresnel lens structures) into hard optical and optoelectronic materials by (reactive) ion beam etching will be summarized.

Smoothing of diamond-turned copper surfaces using ion beams with aid of planarizing film

We investigate ion beam etching that uses a planarizing film for smoothing copper surfaces with nm-order roughness. Copper surfaces were cut using a turning machine with a single-crystal diamond tool to prepare mirror surfaces as workpieces. Then, the surfaces were coated with photoresist, and etched using ion beams with an appropriate incidence angle. As a result, tool marks exhibited on the turned surfaces were removed, and the surfaces with a smoothness of nm order were further improved by the ion beam process.

Sub-nanometer Smoothing of Diamond-turned Metal Surfaces using Ion Beams

We investigated the smoothing effect of ion beam etching with the aid of a sacrificial layer on smoothly cut metal surfaces. Electroplating copper and electrolessplating nickelphosphor were used as specimens to compare their smoothness characteristics. The surfaces were turned by a single-crystal diamond tool, applied with photoresist as a sacrificial layer, and then processed using ion beams. As a result, the heights of the tool marks were successfully reduced on both surfaces, improving the surface roughness. In particular, for the nickel-phosphor, this technique was proven efficient for improving the surface roughness, allowing an rms surface roughness of sub-nanometer order.

Resonant grating pulse compression element with 99% flat top efficiency for high average power femtosecond laser machining

Top hat diffraction efficiency in an all-dielectric SiO2/HfO2 grating femtosecond pulse compression grating is demonstrated with a close to 100% flat top over more than 20 nm around 800 nm wavelength. New perspectives are open for high average power femtosecond laser machining.

Recent achievements on ion beam techniques for optics fabrication

The talk gives an overview on latest results on ion-beam technology development for optics fabrication: RIBE proportional transfer of 3-D micro- and nanostructures, smoothing down to the 0.1nm rms range and figuring below 0.5nm rms.