OPTICAL FABRICATION
“The primary challenge lies in conserving energy or enhancing system efficiency”
processed correctly,” he says. “SCHOTT is committed to supporting the
development of AR, leveraging our heritage in glass science and manufacturing dating back to the origins of the company in 1884. This includes optimising these glass properties – merged in one glass,” he adds.
Melting point As the industry continues to push for a higher and higher refractive index, Bachhuber observes that one of the key challenges currently facing companies engaged in the development and fabrication of optical glass for AR waveguide technologies is the fact that glass melting technology is ‘pushed to its limits’: “It seems almost impossible to melt novel high-index glass types that maintain a good level of the other properties – but our glass lovers at the melt keep on pushing the boundaries. Our journey continues.” Moving forward, Bachhuber is buoyant
about the prospects for continued innovation in this area, and is ‘very confident’ that Schott can achieve super- high-index glass soon. He also confirms he is in ‘constant exchange with the engineers at the melt’ and notes that what they have achieved so far ‘looks very promising.’ “Another promising part of the challenge
is the rise of reflective waveguides, a different technological approach to guide light to the human eye than diffractive waveguides”, Bachhuber continues. “Reflective waveguides require the most demanding homogenous optical glass. What is so crazy about this technology is that, after achieving an extremely homogeneous optical glass that meets the technology’s needs, it requires many challenging processing steps to turn this raw glass into a waveguide. “We are proud to supply Lumus’ core
technology, the Lightguide Optical Element, or LOE, based on reflective waveguide technology,” he adds. More information on Lumus’ reflective waveguide innovations can be found in the article Reflective Waveguides Bring Augmented Reality To Life on
electrooptics.com.
Large-area nanoimprinting Another company active in this area is Danish nano-optics company NIL Technology (NILT), which is involved in the development of innovative approaches to large-area nanoimprinting for the mass production of AR waveguides. As
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FEATURE
Frederik Bachhuber, Senior Innovation Manager for AR at Schott, discusses the optical grating quality of a high-refractive waveguide with a colleague
Theodor Nielsen, Founder and CEO at NILT, explains, a key ambition of AR waveguide companies is to produce units at ‘consumer electronics volumes’ – and develop processes capable of supporting large-scale production. However, because waveguides are ‘the size of glasses’ and ‘only a few fit on a wafer,’ he observes that, from the simple perspective of managing volumes, it ‘becomes attractive to work with large areas.’ “From a processing point of view this is
challenging because nanostructure control is difficult to achieve across very large areas. The most advanced waveguides have complex structures like slanted and blazed gratings, which can be produced on wafers with very high quality, but this needs to be coupled with a large area nanoimprint process,” he says. “There are two approaches to such
processes. One is to scale up a hard pristine master to large areas through step-and- repeat imprinting, a field where EVG is market leader. The other approach is to tile master replicas together to reach display size sub-masters that are used for display size imprinting – here Morphotonics is tech leader,” he adds.
Master roadmap In Nielsen’s view, the main challenges facing optics companies in the development and fabrication of innovative technologies for AR waveguides ‘come in a few different categories’ – and the take-off of AR waveguides will only arrive ‘when one of the big US OEMs launches an elegant product with a great use case.’ However, before this happens, he
believes the industry ‘needs to see a few iterations of VR and MR products with video see through (VST), getting consumers to embrace the idea’. “The process has
A waveguide, or light-guide optical element, manufactured by Schott for Israeli AR firm Lumus
started, and from NILT’s perspective we see a lot of very cool projects that we are working on,” he says. “The quality of the optics in AR waveguides is highly reliant on the quality of the master. At NILT we are developing roadmaps for advancing our masters with key customers, and we are excited about our progress. Of course, these high-quality masters need to work with great optical designs, materials, and high- quality imprinting,” he adds.
Total internal reflection Elsewhere, Ching-Cherng Sun, Professor of Optical Sciences at the Department of Optics & Photonics in the National Central University, Taiwan, explains that the waveguide technology used in AR glasses employs total internal reflection in the glass to guide the image from the panel to the user’s eyes. “Typically, this involves a coupling-
in element to direct incident light into the propagation mode within the glass, and a coupling-out element to extract the light towards the user’s eye. These coupling elements play a pivotal role in the functionality of AR glasses,” he says. Sun and his colleagues used these principles
February 2024 Electro Optics 31
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