FEATURE OPTICAL FABRICATION
Ongoing advances in waveguide fabrication for augmented reality
Optical experts are continually striving for new fabrication techniques to better achieve an optimal balance between brightness, power consumption, weight, heat, battery life and cost for the latest AR headsets
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n recent years, waveguide technologies have emerged as a critical component of augmented reality (AR) devices, and a growing number of companies
and other organisations are now focusing their attention on the development and improvement of waveguide fabrication processes. So, what exactly are waveguides? What are their main applications in AR devices? What have been the key recent advances in waveguide technology? And, what innovations and trends can we expect in the development and fabrication of AR waveguides in the coming years?
High-index glass In basic terms, waveguides are slim pieces of clear glass or plastic capable of
Imec has recently developed a new process for the imprint-and-etch-based patterning of 300mm high-refractive index glass wafers used in AR optical component fabrication. This wafer has been patterned with a range of test structures, all smaller than 1μm
transmitting light in specific ways while maintaining superior optical performance. Waveguide technology is commonly used in lightweight and wearable AR or mixed reality (MR) applications – such as smart glasses or fully immersive devices with a wide field of view (FoV) – to transfer light from one point to another. One company involved in the
development of technology in this area is German speciality glass firm Schott, which in recent years has pioneered a range of high-index optical glass for use in AR waveguide technologies. As Frederik Bachhuber, Senior Innovation Manager for AR at Schott, explains, the latest product development milestone is the Schott RealView 1.9 lightweight ultra, a high- refractive-index glass wafer maintaining a refractive index of 1.9 while shaving 50% off waveguide weight. “This new product also offers an
improved wafer flatness of up to 60%, enabling AR device makers to remove
30 Electro Optics February 2024
“Reflective waveguides require the most demanding homogenous optical glass”
another 30% from the scale for a total weight reduction of 15 grams per device,” he says. According to Bachhuber, glass offers
several advantages over other materials due to its ‘outstanding optical properties’ – making it an obvious choice for AR applications. “First and foremost, light is guided
through a high-index optical glass from a projector to the user’s eye. An optical glass with a high refractive index enables a large field of view, while glass’s high transmission helps to increase battery lifetime. Additionally, an ultra-flat surface of the glass allows for sharp images if
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