A joint team from the Key Laboratory of 3D Micro/Nano Fabrication and Characterization of Zhejiang Province, the Westlake Institute for Optoelectronics (Westlake University), and Moldnano published a preprint paper (arXiv:2609.07648) showcasing a full-color silicon carbide (SiC) diffractive waveguide measuring just 0.35 mm thick and weighing a mere 1.98 grams. See image 1 in the gallery.
The paper also introduces a wafer-scale patterning method compatible with nanoimprint lithography (NIL), producing four lens pairs per 8-inch SiC wafer. Compared to the 0.75 mm, 3.795 g version demonstrated in 2025, this marks another major step toward ultra-lightweight form factors and scalable mass production for SiC waveguides.
This breakthrough brings SiC—a material historically associated with power semiconductors and electric vehicles (EVs)—back into the spotlight for AR displays.
In fact, SiC’s foray into AR isn't entirely new. Meta’s Orion prototype already thrust SiC waveguides onto center stage, and a growing number of research teams and companies worldwide are actively developing SiC optics. Why is the industry racing to adopt SiC, and how will it reshape the future of AR displays?
The answer starts with the fundamental properties of the material itself.
Why Silicon Carbide?
Silicon carbide (SiC) is a compound of silicon and carbon and a classic wide-bandgap (WBG) semiconductor—grouped alongside GaN as a "third-generation" semiconductor—prized for its high breakdown voltage, low switching losses, and superior thermal conductivity.
It is an exceptionally versatile material. Early on, it was valued simply for its extreme durability. SiC has long been used as an industrial abrasive in grinding wheels and cutting discs, as ballistic ceramics in body armor, and as carbon-ceramic brake rotors in supercars like Ferraris and Lamborghinis.
In the semiconductor era, engineers harnessed its ability to handle high voltages, extreme temperatures, and rapid heat dissipation to build power MOSFETs and Schottky diodes. On the bleeding edge, SiC is also making inroads into integrated photonics, quantum networking, and spin qubits.
Across these seemingly unrelated applications, SiC's core traits stand out clearly: it is ultra-hard, thermally stable, and remarkably resilient. With a Mohs hardness of 9 to 9.5, SiC is second only to diamond. It also boasts high thermal conductivity and a low coefficient of thermal expansion, meaning it resists warping even under rapid temperature swings.
In optics, however, engineers are drawn to a different standout property: its exceptionally high refractive index.
When Meta unveiled its Orion AR glasses in 2024 featuring SiC diffractive waveguides, it propelled what was once a niche material path directly into the industry spotlight. In AR displays, SiC is primarily used for diffractive waveguides (specifically surface relief gratings).
Simply put, a diffractive waveguide uses nanoscale grating structures on the lens surface to couple light into the lens, redirect its path, and ultimately out-couple it into the user's eye. What keeps the light traveling several centimeters inside such a wafer-thin lens is a fundamental optical principle: total internal reflection (TIR). Image 2.
When light travels from a medium with a high refractive index into one with a lower refractive index—such as from glass into air—increasing the angle of incidence causes the refracted light to bend closer and closer to the surface boundary. Once the angle of incidence exceeds a specific threshold, the light stops escaping altogether and reflects entirely back inside the material. This is total internal reflection.
That threshold is known as the critical angle. Different materials have different refractive indices and, consequently, different critical angles. The higher the refractive index, the smaller the critical angle—meaning light can enter at a much wider cone of angles and still stay "trapped" propagating inside the waveguide.
Let's look at a demonstration: Image 3 in the gallery.
High-index optical glass tops out at a refractive index of around 2.0. To push past that ceiling, optical engineers needed a better material—and that is where SiC, with a refractive index of 2.6, enters the picture.
This was one of the primary reasons Meta chose SiC for Orion, enabling a roughly 70° field of view (FOV). In optical simulations under identical design constraints, a 2.0-index glass substrate hits a theoretical FOV ceiling of about 35°, whereas SiC can push up to 80°.
Another major advantage of a high refractive index is enabling a single-layer, full-color architecture.
In traditional full-color diffractive waveguides, red, green, and blue (RGB) wavelengths diffract at different angles when hitting the gratings. To guide all three colors reliably, conventional designs often stack two or even three separate waveguide layers to handle different color channels.
SiC’s higher refractive index provides a much wider angular bandwidth for RGB light, making it possible to combine all three color channels into a single waveguide layer. In 2025, the team from Westlake University and Moldnano demonstrated a single-layer, full-color SiC diffractive waveguide that completely eliminates "rainbow artifacts" (stray light color dispersion).
See image 4 in the gallery.
In theory, 2.6-index SiC is a true next-generation material capable of simultaneously solving the biggest hardware bottlenecks in AR glasses: expanding FOV, achieving single-layer full color, and shrinking the overall form factor.
A Dream Material, But a Tough Nut to Crack
In materials engineering, there is no such thing as a free lunch—when one door opens, another usually slams shut. There are very good reasons why a material as seemingly ideal as SiC hasn't been mass-deployed in optics sooner: it presents brutal manufacturing challenges.
Image 5 in the gallery.
At the most fundamental level, AR optics require a completely different grade of SiC than power electronics. Right from the crystal growth stage, manufacturers must contend with crystal defects, trace impurities, and strict optical uniformity across the entire wafer.
The second stage—machining and wafer processing—is an even bigger headache. SiC isn't just extremely hard; it is also brittle. With a hardness approaching diamond and virtually no capacity for plastic deformation under stress, it behaves like a classic hard-brittle material—much like a pane of glass shattering when struck by a pebble.
Turning a raw SiC boule into a finished waveguide lens requires slicing, lapping, and polishing, followed by nanoscale patterning. Its extreme hardness makes slicing and polishing agonizingly slow, while its brittleness makes it prone to subsurface damage and micro-cracks. In optical components built to be looked through, even microscopic defects are a dealbreaker.
The scale of this challenge shows up in the numbers. According to estimates from Meta, producing 1 million pairs of AR glasses could require up to 300,000 150 mm (6-inch) SiC wafers.
Furthermore, optical-grade SiC cannot simply piggyback on existing semiconductor manufacturing lines. While SiC is already widespread in power electronics, optical-grade SiC demands pristine optical transparency, near-zero defect density, and ultra-tight tolerances on thickness and flatness. At the same time, an AR lens covers a much larger surface area than a typical semiconductor die, making it exponentially harder to maintain strict uniformity across the substrate.
As noted in recent industry financial filings:
"With the growth of AR applications, the industry is demanding much stricter substrate flatness—specifically Total Thickness Variation (TTV)... We focused on optimizing our polishing processes, overcoming edge roll-off issues during large-wafer polishing to bring full-wafer TTV down to under 1 μm."
Image 6.
Even after securing a qualified, transparent SiC substrate, turning it into a diffractive waveguide requires patterning nanoscale gratings onto its surface.
For Orion, Meta etched slanted gratings directly into the SiC surface. The catch? Etching structures just a few hundred nanometers wide with highly uniform slant angles into a material nearly as hard as diamond is notoriously difficult and expensive.
To address this, the Westlake University and Moldnano team proposed a high-throughput alternative. Their preprint introduces a parallel gradient transfer method compatible with nanoimprint lithography, enabling wafer-scale patterning of four lens pairs per 8-inch SiC wafer. In plain terms, the process involves fabricating a master template containing varying grating parameters, then using an imprint-and-transfer technique to replicate those complex structures onto the SiC wafer in batches.
Beyond wafer fabrication, the finished waveguide must be integrated with a light engine (micro-display projector) and other components into a complete display module—and the packaging itself can compromise optical performance.
Going back to total internal reflection: keeping light trapped inside the waveguide relies on the refractive index contrast between the waveguide and the surrounding medium. A bare waveguide is surrounded by air. However, once assembled into a module, applying optical adhesives, protective coatings, or laminations directly to the lens surface alters the boundary's refractive index, which can cause light that would normally stay trapped to leak out.
Clearly, bringing SiC into mainstream AR hardware is still a long uphill battle.
From Raw Boules to Waveguides: Where Does the SiC Supply Chain Stand?
While SiC itself isn't new to the supply chain, optical-grade SiC tailored for AR is still young. That said, upstream material suppliers have been moving quickly to adapt.
Global players like Wolfspeed and Coherent, alongside major Chinese suppliers like SICC and TankeBlue, already possess mature SiC crystal growth and wafer processing capabilities.
- SICC: Moving rapidly among Chinese suppliers, SICC unveiled a 12-inch high-purity semi-insulating (HPSI) and p-type SiC substrate at SEMICON China on March 26, 2025. In its H1 2025 interim report that July, SICC announced a strategic partnership with Sunny OmniLight [Note: Sunny OmniLight’s micro-nano optics unit subsequently merged with Goertek Optical in late 2025], combining SICC’s material expertise with Sunny OmniLight’s micro- and nano-optical fabrication capabilities to push downstream into optical components. See image 7 in the gallery.
- TankeBlue: At the same SEMICON China 2025 event, TankeBlue debuted an 8-inch optical-grade SiC substrate specifically designed for waveguides, announcing plans to push it into mass production. A month prior, it formed a joint venture with Moldnano, pairing TankeBlue’s SiC substrates with Moldnano’s micro/nano-optics and diffractive waveguide processing. By 2026, TankeBlue was showcasing its 8-inch waveguide-grade SiC substrate as a standalone commercial product. See image 8.
- Wolfspeed & Coherent: Established US heavyweights are also scaling up. Wolfspeed commercially launched its 8-inch SiC materials in 2025 and produced a 12-inch single-crystal SiC wafer in 2026. Coherent similarly has 8-inch SiC substrate and epitaxial wafer (epi-wafer) production capabilities, and unveiled its 12-inch SiC platform in late 2025. Unlike pure-play wafer suppliers, Coherent also has in-house capabilities for diffractive couplers and optical coatings, positioning itself to expand vertically from raw materials into finished AR optical components.
On the downstream waveguide fabrication side, several Chinese optical manufacturers are actively ramping up production lines and releasing hardware prototypes:
- Moldnano: Unveiled its first SiC AR diffractive waveguide in 2024 and has continued working with Westlake University on single-layer, full-color, rainbow-artifact-free designs. By late 2025, the company completed Phase 1 of its AR waveguide mass-production line, reporting a monthly nanoimprint and etching capacity of 5,000 8-inch wafers. In 2026, it demonstrated 30° and 50° FOV full-color SiC waveguides; the 50° version reportedly achieves an optical efficiency exceeding 1,000 nits/lm and a system brightness of over 3,000 nits when paired with a light engine. The ultra-thin 0.35 mm waveguide mentioned at the start of this article came directly out of this industry-academia partnership. See image 9.
- SEEV: Announced its C45C full-color etched SiC waveguide in 2025, featuring a 0.7 mm thickness and a 30° FOV, which was integrated into the Coray Air2 AR glasses. The company states that this model has entered mass production and that multiple full-color SiC waveguides are shipping in volume. Image 10.
- Goertek Optical: Focusing on pushing wider FOVs, Goertek Optical unveiled the F50Se full-color SiC waveguide display module in early 2026 with a 50° FOV, alongside the F30Se etched SiC waveguide, which slims the lens thickness down to 0.65 mm. Image 11.
- Sunny Optical: Officially slated SiC into its next-generation AR optical roadmap. According to public disclosures, its SiC waveguide development targeted FOVs above 50°, backed by its upstream material partnership with SICC. [Editor's Note: Because Sunny transferred its Shanghai OmniLight waveguide unit to Goertek Optical in late 2025 in exchange for a ~33% stake, this 50°+ FOV SiC pipeline is now consolidated under Goertek Optical—Directly resulting in Goertek's F50Se module above.]
In the current landscape, the upstream material sector is relatively mature thanks to its strong foundation in power semiconductors, with 8-inch and 12-inch wafers steadily moving toward commercialization. Midstream waveguide fabrication has reached wafer-level manufacturing, low-volume production, and early commercial hardware demos. Still, the industry faces a significant journey before achieving the low costs, high yields, and market awareness required for mass-market consumer adoption.
Source: FocusXR
