High-Bandwidth Optical Amplifier Could Deliver Big Gains for AI, Sensing, and More, Researchers Say

A gallium phosphide-based optical parametric amplifier delivers three times the bandwidth of rivals — good news for high-speed systems.

Researchers at the Swiss Federal Institute of Technology Lausanne (EPFL), working with IBM Research Europe, have developed an ultra-broadband amplifier that, they say, could power future optical systems — delivering the high performance required for artificial intelligence (AI) accelerators, high-speed networks, or even optical sensors and lidar.

"This [work] marks, to our knowledge, the first ultra-broadband, high-gain, continuous-wave amplification in a photonic chip," the researchers explain of their creation, "opening up new capabilities for next-generation integrated photonics. We use thin-film gallium phosphide (GaP) on silicon dioxide to create an OPA [Optical Parametric Amplifier] comprising a dispersion-engineered waveguide operating at a pump wavelength near 1,550nm. GaP combines a high optical refractive index with a strong Kerr nonlinearity and an indirect bandgap, sufficiently large to mitigate two-photon absorption at telecommunication wavelengths."

Replacing electrical cabling with optical cabling was one of the biggest breakthroughs in telecommunication, delivering the ability to send increasing volumes of data at ever-higher speeds — and that work continues with attempts to do the same inside computers as outside them, using silicon photonics to accelerate communication between components. For that, optical amplifiers are required — but making ones performant enough to help yet still small enough to fit on a chip is a challenge.

The amplifier developed by the team has a claimed 10dB net gain across a 140nm bandwidth — some three times that of competing solutions — thanks to a spiral waveguide design based around the concept of optical nonlinearity, where light is amplified through contact with specific materials. The technique, the researchers claim, could be used to produce a chip-scale amplifier delivering 35dB at a low noise level — making it suitable for use cases beyond high-speed communication and into optical sensor systems, including lidar.

The team's work has been published in the journal Nature under open-access terms.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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