Mastering the master: surface relief grating masters for AR, VR, and MR applications

Augmented, virtual, and mixed reality devices increasingly rely on compact and efficient optical elements to guide and shape light into the user's eye. A key enabling technology for these devices is the use of surface relief gratings (SRGs) as optical in- and out-couplers within diffractive optical waveguides. A critical performance requirement is achieving uniform illumination of the eye-box, which ensures image clarity and consistency across the viewing area. To manufacture such high-performance SRGs, nanoimprint lithography (NIL) combined with direct etching techniques has proven effective. However, nanoimprint methods require the prior fabrication of a master stamp, which is a highly precise template that defines the nanoscale surface features to be replicated during the NIL process. This work demonstrates the nanopatterning capabilities of slanted and blazed SRGs in terms of sidewall angle, modulation of pitch and critical dimension, continuous depth variation and shape fidelity control by using advanced electron beam lithography and reactive ion beam trimming etching techniques.