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Photonics Europe Digital Forum: silicon photonics to make waves beyond telecoms

08 Apr 2020

Virtual conference hears that new applications and markets will likely eclipse current use of the technology in communications.

Silicon photonics has “endless potential” in applications beyond its current use in telecoms and datacoms, and is likely to create major new markets as the technology migrates to different wavelength regimes.

That was one of the key messages from Ghent University professor Roel Baets, in a conference presentation for this week’s SPIE Photonics Europe Digital Forum.

The virtual conference is taking place this week, as a replacement for the original event planned for Strasbourg, and features more than 750 technical presentations.

Technology flavors
Baets, who also works at IMEC in Belgium, outlined the past, present, and future of silicon photonics, in a talk acknowledging the key contributions of recently retired CEA-Leti professor Jean-Marc Fedeli.

“It’s quite clear that silicon photonics is here to stay,” Baets remarked in his conclusion. “There are millions of silicon photonics transceivers in the market.”

And while the overall market for silicon photonics has been driven almost entirely by applications in telecom and datacom transceivers thus far, things look set to change in the future.

“There is really an endless potential, and with time it’s likely that new applications and markets will become considerably larger than what we know of the telecom and datacom field.”

“But, of course, with new applications there are new needs - and that’s why we see many new technology ‘flavors’ emerging, covering new wavelength ranges from visible to mid-infrared,” added Baets

Sensing opportunities
He outlined numerous potential applications that could benefit from the combination of chip-scale miniaturization and low-cost manufacturing that silicon photonics brings, among them lidar, spectroscopic sensing, gas and glucose monitoring, optical coherence tomography, laser Doppler vibrometry, and more.

Adjusting to wavelengths either longer or shorter than the telecommunications band in the near-infrared necessitates a change in the materials deployed within the semiconductor wafer, Baets explained.

Whereas communications applications have benefited from the inherent high refractive index contrast between silicon and silicon oxide - helping to confine light within photonic circuits very effectively - those properties do not extend far beyond the near-infrared.

But it is still possible to piggy-back on the vast global investment in silicon CMOS wafer processing fabrication, by instead adopting silicon nitride for visible-range confinement, and germanium-on-silicon architectures for mid-infrared applications.

Devices and applications based on those material combinations are already under investigation within two of Europe’s pilot line projects, namely PIX4Life and MIRPHAB.

In another presentation during the Photonics Europe Digital Forum, IMEC's Adil Masood said that PIX4Life will continue to operate beyond the scheduled completion of the European project period later this summer. The event also heard updates from silicon photonics platforms including Cornerstone in the UK, and VTT in Finland.

Open access key
Baets believes that the combination of these open-access approaches for early-stage research and prototyping with industrial-scale platforms elsewhere will prove critical to the future, as silicon photonics moves beyond telecoms.

“There is a strong traction, really, towards open-access industrial manufacturing in CMOS fabs,” he said. “And that's obviously what you need when end users move to high-volume products.”

In closing, Baets also paid tribute to the pioneering work of Fedeli, whose Leti team has devised numerous breakthrough devices and approaches.

Those include grating couplers, high-speed germanium photodiodes and silicon modulators, and silicon nitride waveguides, as well as key work on III-V/silicon integration, and establishing between Leti and IMEC the multi-project wafer (MPW) format that has been widely adopted across the silicon photonics ecosystem.

“It is nice to see that we have a variety of access modes to the platforms, either research platforms or industrial platforms, all the way from MPW to volume manufacturing,” Baets added.

• The SPIE Photonics Europe Digital Forum takes place online 6-10 April. To view presentations and manuscripts, and interact with speakers, visit the virtual event's dedicated web site.

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