The interest for nanoimprint lithography (NIL) as enabling technology for applications in the field of photonics, solar, lighting and displays is growing. The quality, flexibility in design, the relative ease and competitive costs at which surfaces can be patterned makes NIL a groundbreaking technology. While the added value of imprinted light management crystallizes, the need for high-volume NIL production methods becomes more urgent. The Roll-to-Plate (R2P) imprint technology can enable mass volume production, having the opportunity for large area imprinting, manufacturing higher numbers of smaller products in a single imprint step. In this presentation the replication process and quality of the Morphotonics GEN5 R2P imprint equipment will be discussed.
In a waveguide-type display for augmented reality, the image is injected in the waveguide and extracted in front of the eye appearing superimposed on the real world scene. An elegant and compact way of coupling these images in and out is by using blazed gratings, which can achieve high diffraction efficiencies, thereby reducing stray light and decreasing the required power levels. This study investigates the fabrication of blazed gratings with grayscale electron beam lithography and the subsequent replication of the realized 3D grating structures in a polymer material with ultraviolet nanoimprint lithography. As such, diffractive elements are realized on a waveguide sheet, with very good control over the dimensions and the profile of the printed features. Blazed gratings are designed for green light (λ= 543 nm) and a diffraction angle of 43°. Making use of a PMMA resist and by carefully optimizing the electron-beam parameters, electron dose distributions and development step, blazed gratings with a pitch of 508 nm and a fill factor of 0.66 are achieved. Finally, a master is realized with two blazed gratings, 3 cm apart, which are replicated using ultraviolet nanoimprint lithography onto a waveguide sheet. The in- and outcoupling of an image through these two blazed gratings is shown, appearing sharp and non-distorted in the environment, and a throughput efficiency of 17.4% is confirmed.
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