Low-loss glass for RF and photonics: From Ka-band modules to co-packaged optics

As radio frequency front‑ends extend into Ka‑band (about 26.5-40 GHz) and data‑center networks advance toward co‑packaged optics, engineered low‑loss glass substrates valued for high resistivity, dimensional stability, and compatibility with through‑glass‑via interconnects are emerging as an integration platform for antenna‑in‑package modules and optical‑electrical co‑design alike, as discussed in IDTechEx's brand‑new report "Glass in Semiconductors 2026-2036: Applications, Emerging Technologies, and Market Insights".

Beyond compute: Why RF and optics pull on glass?
As networks scale for artificial intelligence (AI) clusters and bandwidth‑hungry data center fabrics, radio frequency (RF) front‑ends and optical links are moving closer to switches and accelerators, elevating packaging materials that minimize loss and simplify optical coupling.

Glass brings high resistivity, low dielectric loss, and optical transparency, making it attractive for Ka‑band devices and emerging co‑packaged optics (CPO) concepts, where electrical and optical paths converge within the package. Recent collaborations in the ecosystem, including demonstrations and partnerships around CPO building blocks, underscore a growing focus on integration paths that leverage glass's distinctive properties.

Material advantages at high frequency and light
Compared with many organic laminates, engineered glass compositions can offer lower loss tangent and smoother surfaces, reducing conductor and dielectric losses for RF lines at tens of gigahertz and above while supporting fine geometry stability over large areas.

SCHOTT's AF 32 eco and related families highlight low coefficients of thermal expansion (CTE) and dielectric behavior compatible with high‑frequency routing and precise assembly, attributes that directly impact insertion loss and matching networks in compact RF modules. These same attributes also provide a mechanically stable, low‑scatter medium for optical elements, allowing optical paths to be co‑fabricated near electronics without the parasitics introduced by lossy or warpage‑prone cores.

Waveguides and vertical transitions in glass
Co‑packaged optics benefits from glass's ability to host ion‑exchanged or etched waveguides that route light with low loss, aligning directly to fibers or photonic chiplets at short distances within a package. Because the through‑glass via (TGV) toolbox developed for electrical interconnect can also inform vertical optical transitions and alignment features, a single glass core can, in principle, support both high‑speed redistribution and optical waveguides with fewer stacks and interfaces.

This co‑habitation reduces alignment burden and packaging steps compared with using separate silicon photonics interposers plus an electrical substrate, provided process control and coupling efficiency are demonstrated at scale.

Co‑design of electrical redistribution and optics
A central promise of co‑packaged optics (CPO) is collapsing the electrical channel length and bringing fiber attach to the substrate plane, which in a glass core can coincide with low‑loss copper redistribution layer (RDL) stacks and planar optical routing features.

Demonstrated building blocks from ecosystem leaders show feasibility for co‑integrating driver/receiver electronics, optical engines, and coupling structures, with glass serving as the neutral medium that supports both domains. System‑level benefits such as lower power per bit and reduced front‑panel congestion are contingent on maturing co‑design flows and manufacturing proof that optical and electrical tolerances hold across production panels.

Manufacturing enablers and pain points for RF/optics
RF modules on glass require tight control of surface roughness, metal thickness, and via integrity to sustain predictable impedance and low insertion loss across wide bands, tying performance directly to metallization and planarization discipline inherited from advanced packaging.

For optics, low‑loss waveguide formation, facet quality, and robust fiber attach in a panel context must coexist with electrical process steps, which elevates the role of metrology, stress management, and edge‑defect suppression in thin glass. The overlap of TGV drilling, plating, and inspection with optical fabrication steps argues for integrated lines and recipes explicitly optimized for co‑habitation, rather than bolt‑on sequences after electrical processing.

Ecosystem momentum and realistic timelines
Industry signaling suggests glass is being positioned as a platform material for next‑generation optics near switch ASICs, reinforced by supplier commentary on rising CPO readiness, as AI traffic scales and electrical reach limits loom.

In the broader glass‑substrate ecosystem, efforts by Intel, Absolics, and materials vendors establish the infrastructure and knowledge base that RF and optical variants can leverage, even though high‑volume adoption remains dependent on multi‑year process and cost maturation. The prudent expectation is iterative deployments in tightly scoped modules before broad roll‑outs, aligned with verifiable manufacturing data and interoperable design flows.

Conclusion
In RF and photonic packaging, engineered glass combines low dielectric loss and optical transparency to enable Ka‑band modules and CPO, but broad adoption still hinges on manufacturing proof that co‑fabricated waveguides and electrical RDL can meet insertion loss, alignment, and reliability targets at panel scale.

Progress across ecosystem collaborations suggests a viable path, yet repeatable yields in TGV‑enabled electrical stacks and optical coupling structures will determine when deployment moves from pilots to selective production. 

-- Dr Xiaoxi He, Research Analyst, IDTechEx.