IBM spin-off brings barium titanate to silicon photonics

July 11, 2021 // By Peter Clarke
IBM spin-off brings barium titanate to silicon photonics
Lumiphase AG (Zurich, Switzerland) is a spin-off from IBM Research applying the electro-optic material barium titanate (BaTiO3 or BTO) to silicon photonics.

Founded by a research team from IBM in January 2020 Lumiphase now has a foundry processing wafers on its behalf and three customers, according to co-founder and co-CEO Lukas Czornomaz. 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.

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 10x greater in BTO than it is in silicon, the company asserts. A lot of the company's value comes in its ability 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.

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. In some applications this is done with hundreds or thousands of on-chip heaters that consume tens of milliwatts of power each. Only certain applications require hundreds or thousands, such as AR/VR or LiDAR, optical communication applications require tens of them, Czornomaz added.

Because of the way BTO modulates the optical signal such tuning, while still required does not consume static power, Czornomaz said.

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

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