Silicon Photonics—technology of the future for bandwidth-hungry applications

Senior Scientist, Dr. Yves Painchaud (front centre), Carl Paquet (front left), and Martin Pelletier (front right) as well as other members of TeraXion’s R&D team

For more than a decade, Québec City-based TeraXion Inc. has designed and manufactured state-of-the art optical components for the telecommunications industry. The company has developed its reputation for sustaining innovation through proprietary fiber Bragg grating (FBG) and laser frequency control technologies. And while those competitive products continue to account for the bulk of the company’s revenues, TeraXion anticipates that new silicon photonics technology is critical to future innovation.

By 2009, customers were expressing a significant need for more highly integrated systems with smaller footprints. According to senior scientist Dr. Yves Painchaud, TeraXion investigated various options and decided to target silicon photonics as the best technology to meet this demand.

Painchaud recalls how the first steps toward this kind of capability were facilitated by CMC Microsystems, initially through a silicon-nanophotonics course offered in partnership with University of British Columbia. The course was developed to give researchers across the country fast-tracked exposure to emerging silicon-on-insulator (SOI) technology including the design, fabrication and test of photonic integrated circuits (PICs). Participants could quickly get up to speed with the technology, starting the design phase using tools such as dw-2000 from the Canadian-based Design Workshop Technologies, followed by fabrication of the design through multi-project wafer (MPW) shuttles organized by ePIXfab in Europe, and finally testing of the manufactured chips. “Our interaction with CMC was extremely valuable,” says Painchaud. “It was an opportunity for us to see more clearly how silicon photonics could perform.”

Following the course, TeraXion continued developing expertise in silicon photonics. The company saw opportunities to leverage CMC’s fabrication services for their commercial R&D efforts by joining scheduled multi-project wafer runs. Their design was implemented on a single wafer along with that of other researchers and this aggregation significantly reduced their barriers to entry. Within a year, Painchaud and his colleagues had fleshed out the mechanical and electrical aspects of their new product and the considerable time usually needed to introduce new technology was effectively reduced.

“Everything is put into an RF-compatible package,” he explains, adding that the metallized silicon photonics die is attached and wire bonded on a high-grade ceramic. The company targets a fab-less approach for the photonic chip but not for its packaging. In-house skills were enhanced such as wire bonding and flip-chipping in order to develop the packaging and master the quality of the new products.

Thanks to its specific silicon-on-insulator geometry, silicon photonics allows highly confined submicron waveguides, resulting in very compact photonic circuits. The need for such compact packaging was also the reason that silicon was chosen for the platform. “When we were investigating photonic integration in general, we looked at different platforms, and we believed that silicon photonics was the best choice for us,” observes Painchaud. “It’s very close to a CMOS process, benefitting from decades of development in that field.”

The next stage of this development consists of qualifying the new product, a small form factor integrated coherent receiver, according to the internationally accepted Telcordia telecommunication environmental standards, which are noteworthy for demanding thousands of hours of operation under high temperature and humidity conditions. “We have tested the functionality of the device, which is fully packaged but is not qualified yet,” he says.

TeraXion has other plans for silicon photonics products where size and power consumption are critical for new high-speed applications. The company recently announced a new line of silicon-based 40 and 100 gigabit coherent receivers which will be available in sample form in 2013. TeraXion will exploit the full benefit of silicon photonics by offering ultra-compact coherent receivers for the second generation of 100 Gb/s system where the small footprint will become a crucial specification. “We’re looking at silicon photonics as the technology of the future,” concludes Painchaud.

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