Improving Surface Relief Gratings: Multi-Depth Approaches at Different Angles for NIL Master Stamp Production

Augmented reality (AR) and mixed reality (MR) have swiftly transitioned from a futuristic concept to a practical technology, altering the landscape of numerous sectors, including education, healthcare, manufacturing, and entertainment. AR and MR enhance the real world by overlaying it with digital information, blending virtual and physical elements seamlessly, thus creating an immersive experience. This growing impact is evident as AR and MR devices become more sophisticated, user-friendly, and accessible, leading to their increasing adoption and integration into everyday life. 

State-of-the-art AR and MR devices use optical waveguides with diffraction gratings to guide light from a display by total internal reflection (TIR) into the human eye’s field of view (FOV). These so-called surface relief gratings (SRG) are essential in AR/MR waveguide displays.

Nanostructuring plays a key role in the fabrication of these surface relief gratings (SRGs). For the development of lightweight near-eye displays, SRGs are employed to couple light from the source into the waveguide and then guide it out toward the eye. Ion beam trimming is a well-established technique used primarily in the MEMS industry to locally modify the thickness of functional layers on a substrate.  This method has been adapted as a versatile approach for creating SRGs with varying trench depths.

This study demonstrates how reactive ion beam trimming can be utilized to produce slanted surface relief gratings, featuring different grating geometries in terms of width and pitch suitable to the specific requirements of nanoimprint lithography.