Gratings for synchrotron and FEL beamlines: a project for the manufacture of ultra-precise gratings at Helmholtz Zentrum Berlin

Abstract

Blazed gratings are of dedicated interest for the monochromatization of synchrotron radiation when a high photon flux is required, such as, for example, in resonant inelastic X-ray scattering experiments or when the use of laminar gratings is excluded due to too high flux densities and expected damage, for example at free-electron laser beamlines. Their availability became a bottleneck since the decommissioning of the grating manufacture facility at Carl Zeiss in Oberkochen.To resolve this situation a new technological laboratory was established at the Helmholtz Zentrum Berlin, including instrumentation from Carl Zeiss. Besides the upgraded ZEISS equipment, an advanced grating production line has been developed, including a new ultra-precise ruling machine, ion etching technology as well as laser interference lithography. While the old ZEISS ruling machine GTM-6 allows ruling for a grating length up to 170 mm, the new GTM-24 will have the capacity for 600 mm (24 inch) gratings with groove densities between 50 lines mm À1 and 1200 lines mm À1. A new ion etching machine with a scanning radiofrequency excited ion beam (HF) source allows gratings to be etched into substrates of up to 500 mm length. For a final at-wavelength characterization, a new reflectometer at a new Optics beamline at the BESSY-II storage ring is under operation. This paper reports on the status of the grating fabrication, the measured quality of fabricated items by ex situ and in situ metrology, and future development goals.

Damage thresholds for blaze diffraction gratings and grazing incidence optics at an X-ray free-electron laser

“…1) were produced at the grating laboratory of the Helmholtz Zentrum Berlin (HZB) (Siewert et al, 2018). The gratings are mechanically ruled, using a Zeiss GTM-6 ruling machine (Loechel et al, 2013).…”

Realization of wafer-scale nanogratings with sub-50 nm period through vacancy epitaxy

“…Current commercial gratings used for EUV and soft X-ray regions are generally fabricated by mechanical ruling, or laser interference lithography techniques and have a typical groove density of no more than 5000 lines mm −1 (see refs. 20,21 ). Even higher-line density, e.g., 10,000 lines mm −1 , blazed gratings have been demonstrated by e-beam lithography and the anisotropic etching of silicon single crystals 22 .…”

Ultra-low blaze angle gratings for synchrotron and free electron laser applications

“…Similar blazed gratings are needed for Free Electron Laser (FEL) applications [4] since they offer much higher stability over lamellar gratings which suffer from laser ablation damage of their rectangular grooves [5]. The off-plane diffraction mount of lamellar gratings was suggested to avoid ablation and achieve high diffraction efficiency [6].…”

“…Since it is challenging to rule perfectly triangular grooves with blazed angles smaller than 3-5°, an additional process of reduction of the blaze angle is required. In this process, the blazed grooves ruled into a metal layer are transferred to the underlying Si substrate by an ion beam etching process [4,8,9]. Owing to the difference in the sputter yield of the metal and Si under bombardment by high energy ions of a noble gas, the transferred grating has a reduced groove depth and a lower blaze angle.…”