Video presentation: Direct etching of slanted gratings for waveguides

In this video presentation, Sales Director Marcel Demmler 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 of the gratings has to be smaller than 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. Marcel Demmler will introduce a reactive ion beam milling tool for manufacturing of those gratings in mass production. He concludes by showing examples of how process parameters can be varied in order to control the grating geometry.

Here you can see the presentation.