Meta: Why We Chose SiC？
March 10, 2025
March 6, Meta (formerly Facebook) published an article on its official website detailing the journey and advantages of selecting silicon carbide (SiC) as the core material for its AR glasses' waveguide technology.
Meta’s team not only resolved critical bottlenecks in AR glasses such as field of view, weight, and optical artifacts using SiC waveguide technology but also positioned it as a "game-changer" for the AR industry, which may become the mainstream material in the future:
Why Meta Orion Team Chose SiC Technology
In 2019, the Orion team prepared a pivotal demonstration for Meta CEO Mark Zuckerberg, showcasing potential waveguide technologies for augmented reality glasses. This marked the first time theoretical calculations transitioned into reality, fundamentally altering subsequent R&D trajectories.
Meta optical scientist Pasquale Ribera recalled: "Wearing glasses with glass-based waveguides and multi-layer laminates felt like being in a disco hall—filled with rainbow-colored light spots that severely distorted visibility. However, switching to a SiC waveguide prototype was akin to stepping into an opera hall, where focus remained on our meticulously crafted experience. This completely rewrote the rules."
Despite SiC’s seemingly obvious advantages today, its adoption as a substrate material was far from straightforward a decade ago when Meta began developing AR glasses. Ribera explained that silicon carbide, typically heavily doped with nitrogen, appears green or even black if thick enough. Such a material was unsuitable for optical lenses, being inherently an electronic material tied to color and electronic properties.
Giuseppe Caraffiore, Meta’s lead AR waveguide technologist, added: "Silicon carbide has long been used in high-power electronic devices, such as EVs. Every electric vehicle requires chips that withstand extreme power to drive motors and systems—conventional silicon substrates cannot meet this demand, only materials like SiC, which allow high current and power densities." While high-power chip markets were smaller before renewable energy gained momentum, SiC’s prices remained prohibitive due to limited automotive substrate demand. Manufacturers lacked incentives to reduce costs.
Yet SiC also possesses critical optical properties. Meta prioritized refractive index—a parameter where SiC excels. High refractive index enables transmitting massive optical data (analogous to internet bandwidth), with higher refractive materials allowing broader optical expansion and wider field of view (FOV) through waveguides.
SiC’s Refractive Index Surpasses Traditional Materials
In 2016, when Caraffiore joined Oculus Research (now Meta), the highest refractive index glass available was 1.8. Achieving target FOVs required stacking multiple glass layers, leading to complex assembly processes, excessive weight, and thickness. "No consumer would buy such a product," he noted. The team explored niobium lithium (refractive index ~2.3) before discovering high-purity SiC’s transparency in 2019.
SiC’s refractive index of 2.7—a record for optical materials—represented a 17.4% increase over niobium lithium and 50% over glass. By adapting industrial equipment to prioritize optical properties (transparency, refractive uniformity) over electronic traits, Meta achieved its goals.
Overcoming Artifacts and Rainbow Effects
Reality Labs’ initial transparent SiC wafers were costly due to extreme hardness requiring diamond tools for cutting/polishing. Despite cheaper alternatives, Meta chose SiC for performance-critical applications.
New challenges emerged, such as ghosting (repeated images) and rainbow effects (dynamic color fringes from environmental reflections). For example, car headlights at night could create rainbow glare, or sunlight during beach volleyball might distract users. SiC’s unique properties eliminated these issues.
Thermal Advantages and Lightweight Design
SiC’s exceptional thermal conductivity (superior to plastics, glass, and niobium lithium) revolutionized design. In July 2020, Meta finalized SiC for three reasons:
- Form Factor: Single-layer substrates reduced device size.
- Optics: High refractive index and anti-rainbow performance improved display quality.
- Weight Reduction: Significantly lighter than double-glass solutions.
Scaling Production Through Innovation
Post-material selection, Meta tackled waveguide manufacturing challenges, particularly slanted etching—a non-traditional nanolithography technique. While others used nanoimprint, Meta became the first to implement slanted etching directly on devices. Partners customized equipment, and Meta developed proprietary processes from research to mass production.
Cost Reduction and Industry Collaboration
Current SiC substrate costs are falling due to oversupply in the EV sector. Suppliers globally are now exploring optical-grade SiC opportunities. Transitioning from 6-inch to 12-inch wafers could exponentially boost AR glass production.
A New Era for AR
While alternatives remain under exploration, Meta’s consensus is clear: SiC will revolutionize AR glasses during the right market window. Caraffiore emphasized that every tech revolution (e.g., TVs evolving from CRT to MicroLED) involves iterative exploration. SiC’s cross-disciplinary potential—spanning electronics, photonics, quantum computing—and cost reduction trajectory make it a transformative material.
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