Physics / mechanism
Barium Titanate (BaTiO3, BTO) is a ferroelectric oxide with one of the largest known Pockels coefficients (>358 pm/V on optimised platforms vs. ~30 pm/V for lithium niobate). Used as a thin-film electro-optic layer integrated with silicon photonics or silicon nitride, BTO modulators show VπL of 0.2 V·cm and tuning at sub-µW power — orders of magnitude better than LN. Frequency response measured continuously from 100 MHz to 330 GHz. Foundry-compatible processes for BTO thin films on oxide insulators are advancing rapidly; the gating step is a production-grade, qualified BTO process at a major foundry (UCL/Altro is targeting GlobalFoundries collaboration). 2-3 BTO startups emerging every 6 months.
Competitive landscape
Adjacent material classes / techniques.
Yield, integration & material quality
Expert read from George Li (ex-Harvard BTO thin-film grower; 2026 06 07 George Bto Question Feb Call) — the load-bearing constraints behind BTO’s slow path to production, and why the headline Pockels spec overstates the practical case:
- Monolithic BTO is a yield problem, not a capex problem. BTO thin films are hard to grow well, and even when you get a film the ferroelectric domains orient randomly across the wafer (distribution varies with thickness, deposition, and epitaxy). Monolithic etched waveguides therefore effectively require poling. With no foundry or wafer supply chain to absorb the process risk, a company funds both the process and the ecosystem from scratch (e.g. PsiQuantum running their own MBE machines for wafers, the “bottomless pit”).
- The manufacturable path is heterogeneous, not monolithic. SiN strip-loaded on top of BTO (the PsiQuantum route, also the GF SiN-on-BTO hybrid stack) does not etch the BTO, so it sidesteps the domain problem entirely. The trade-off: you lose the raw-BTO on-paper specs (real performance falls short of the >358 pm/V headline), but it is much cheaper than monolithic BTO. George: “monolithic BTO probably doesn’t make a lot of sense.”
- Wafer availability is not production-grade quality. La Luce Cristallina’s 200mm BTO wafers are sputtered, multi-crystalline films, not single-crystal (George, ~3 yrs ago: worse than Harvard-grown; doubts a single-crystal thin film within 3 years). Sputtered films are useful as a heterogeneous-deposition method onto Si/SiN, not as a monolithic waveguide layer.
- Demand pull (2026): a datacom systems CEO does not need BTO for 400G/800G today (SiPho + TFLN are good enough); BTO’s near-term entry is the quantum corner (low-loss, fast switching). See Photonics Material Class War — BTO as a 2028-plus niche behind TFLN.
Companies using
Connected ideas
Sources
Frontier (open questions)
- Does any foundry list a single-crystal (not sputtered) BTO process module on a public PDK by 2028? (Leading indicator for Photonics Material Class War prediction 3.)
- Does the heterogeneous SiN-on-BTO route recover enough of BTO’s raw EO advantage to beat TFLN on Vπ·L in production, or does the spec gap erase the headline win?
- First non-quantum (datacom/telecom) BTO design-in, and at what data rate? (Pull today is quantum-leaning; volume pull is absent.)
- Can sputtered/poled multi-crystalline films ever reach production-grade photonic loss, or is single-crystal MBE the only viable route?
Primer (web-enriched)
Sourced 2026-05-02. See sources/web/ for full citations.
Barium Titanate (BaTiO3, BTO) is a ferroelectric oxide with one of the largest known Pockels coefficients (>358 pm/V on optimised platforms vs. ~30 pm/V for lithium niobate). Used as a thin-film electro-optic layer integrated with silicon photonics or silicon nitride, BTO modulators show VπL of 0.2 V·cm and tuning at sub-µW power — orders of magnitude better than LN. Frequency response measured continuously from 100 MHz to 330 GHz. Foundry-compatible processes for BTO thin films on oxide insulators are advancing rapidly; the gating step is a production-grade, qualified BTO process at a major foundry (UCL/Altro is targeting GlobalFoundries collaboration). 2-3 BTO startups emerging every 6 months.