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We will introduce the latest results for etching of slanted relief grating (SRG) used as in- and out-coupling gratings in waveguides for augmented or mixed reality devices. The smaller input grating diffracts light coming from a display into the waveguide. At the out-coupler grating, light is diffracted in direction of the viewer. The geometrical dimension is below the wavelength of the light. Different approaches for the design of coupling gratings exist. One type is the so called SRG, which has a higher coupling efficiency compared to other types. For SRG, tilted trenches are etched in the waveguide, which is typically a plate made of a high refractive index material. The manufacturing challenges are the control of etching depth, slant angle and bottom angle. We will introduce a reactive ion beam milling tool for manufacturing of those gratings in mass production. We will give examples how to vary process parameters in order to control the grating geometry.
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