Material boost for silicon photonics

July 12, 2021 // By Peter Clarke
IBM spin-off brings barium titanate to silicon photonics
Lumiphase in Zurich is supplying three customers with barium titanate (BaTiO3 or BTO) for silicon photonics

In just over a year, Lumiphase in Zurich has a foundry processing wafers for barium titanate (BaTiO3 or BTO) for silicon photonics. The company is processing wafers for itself and three customers, according to co-founder and co-CEO Lukas Czornomaz.

Founded by a research team from IBM in January 2020, Lumiphase has developed processes to include BTO modulators within silicon, or silicon nitride waveguides allowing the construction of Mach-Zhender interferometer and other optical processing devices. The electro-optical effect is ten times greater in BTO than it is in silicon and the company has developed techniques to smoothly integrate BTO with silicon waveguides and control the crystal orientation with relation to the optical path and the electric field direction.

Traditionally some electro-optical conversion is done using germanium and or compound semiconductor materials because silicon is not a natural emitter of light or the most efficient detector. However, the use of BTO brings multiple advantages including lower voltage operation beyond 70GHz and 10x lower optical loss and 1000x lower static power consumption.

The company has 15 staff and raised a seed round of funding soon after its formation with IBM providing a license to use the technology. "IBM is a partner but not a shareholder," said Czornomaz. A Series A round of funding is planned for later in 2021 or early 2022. This should enable first product releases to come in 2023, Czornomaz said.

Czornomaz declined to name either the customers or the foundry but said the technology represents a superior approach to silicon-based photonics with applications in optical communications and solid-state lidar. When asked when whether the company was in production on 200mm- or 300mm-diameter wafers, Czornomaz said the BTO processing was compatible with both wafer sizes.

In bulk BTO is a high value dielectric and piezoelectric material and it was a team at IBM looking at high-k materials for semiconductor gates that started the research path because in sufficiently thin films it can be used to perform electro-optic modulation.

Czornomaz explained the static power consumption is because silicon photonics chips traditionally require a lot of active tuning circuitry to compensate for variation in manufacturing, temperature of operation and aging. And this is done with hundreds or thousands of on-chip heaters that consume tens of milliwatts of power each. Because of the way BTO modulates the optical signal such tuning is not required, Czornomaz said.

The technology also works across the optical spectrum at 1550nm, 1310nm and 1600nm wavelengths.

The company is working towards a product business model where it will provide silicon photonics chips allowing its customers to make optical modules for telecommunications and data communications applications.

Related links and articles:

www.lumiphase.com

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