Developments in SRG Diffractive Waveguides for AI Glasses

2026 is an exciting time for smart glasses, with several products expected to be launched from big tech players later this year, which will follow Meta's release of the Ray-Ban Display launched in September 2025.

 

The optics required to give AI smart glasses augmented reality (AR) capabilities are called waveguides and are positioned within the eyepiece. There have been several key developments to waveguide technology which are enabling AR smart glasses which are lightweight, have longer battery life, and have a fashionable form factor. IDTechEx forecasts 35 million AR smart glasses to be sold annually by 2036.

 

Surface Relief Grating (SRG) waveguides are one of several optics technologies which are being developed for AR smart glasses. Within this technology there are a wide variety of materials options and manufacturing techniques, and SRG waveguides are one of the most promising technologies for use in AR smart glasses. To find out more about other optics technologies used in both AR and VR, see "Optics for Virtual, Augmented and Mixed Reality 2026-2036: Technologies, Players and Markets". IDTechEx's report covers the key market trends in extended reality (XR) devices, covering the various optics technology options, player developments, benchmarking metrics and providing granular market forecasts.

 

SRG waveguides perform well comparatively to other waveguides. They enable a wide field of view of the digital image, at a low thickness. However, the enabled optical effiency will likely always remain below reflective waveguides despite recent improvements.

 

It is important to note that waveguides should be judged in their final application, as often factors must be co-optimized and compromises made depending on the factors which are most important in the specific usecase. For example, where battery life or outdoor use is most important, otpical efficiency may be valued over the enabled field of view or thickness and weight of the waveguide. Furthermore, waveguides must be co-optimized with a light engine (projector), to ensure highest performance in a final device.

 

SRG waveguides, in their simplest form, first receive light which is output from a projector, usually positioned in the frame of the glasses. This light hits an optical element which comprises a surface grating structure. The structure diffracts the light into the waveguide. The light then bounces through the waveguide by total internal reflection before reaching another surface grating optical element which diffracts the light, and the image, to the eye. This enables the user to see the digitally generated image, alongside being able to see through the smart glasses and see the real world.

 

 

 

There are a wide variety of grating structures which can be used in SRG waveguides, and tuning these can help aid metrics such as optical efficiency, and reducing eye leakage, or eye glow. Structures can be optimized by varying the slant angle and aspect ratio of the structures. The structures can also be binary, such as those used in the past by Meta, and WaveOptics, or analogue, such as those used by Magic Leap. SRG waveguide players are likely to be investigating a wide variety of grating architectures, to optimize their products for final application in end products.

 

There are also a wide variety of materials and manufacturing technique options. The base substrate is often glass or polymer based, although advanced materials such as silicon carbide can also be used. The grating structure can then be produced by nanoimprint lithography, typically using a resin with refractive index of around 1.5, although up to 1.9 can be used. This approach results in a residual layer thickness of resin on the waveguide substrate which can result in unwanted reflections which reduce the enabled field of view of the end device. Techniques to make this residual layer as thin as possible are therefore key.

 

An alternate approach could be atomic layer deposition, followed by etching, which can result in a grating with a refractive index higher than the substrate. This enables smaller aspect ratios whilst still providing strong diffraction. Each manufacturing and material approach may have differing performance advantages. They will also have varying cost, and enable differing manufacturing yields, which can also have a big effect on which technology is preferred.

 

SRG waveguides are highly competitive amongst other AR optics technologies. Combined with reflective waveguides, IDTechEx forecasts that these technologies will represent over 70% of the smart glasses optics market in 2036. Other technologies, such as birdbath combiners, are expected to be a niche. Within SRG waveguides, the proportion of which are polymer as opposed to glass, is expected to grow steadily throughout the forecast period.

 

If you are interested in finding out more about SRG waveguides, alongside the AR smart glasses market and VR market, see "Optics for Virtual, Augmented and Mixed Reality 2026-2036: Technologies, Players and Markets". The report outlines how optics technologies are enabling next-generation devices within these markets, providing forecasts, technology benchmarking, and player analysis.

 

For more information on this report, including downloadable sample pages, please visit www.IDTechEx.com/ARVROptics, or for the full portfolio of XR research available from IDTechEx, see www.IDTechEx.com/Research/XR.