Optical/IP Networks

Dutch Startup Seeks Passage to Indium

ThreeFive Photonics thinks it can succeed where others have failed. It's planning to make chips that integrate multiple optical functions on a single piece of indium phosphide.

A spin-out from Delft University of Technology in the Netherlands, ThreeFive Photonics has just got going. It's about to announce seed funding of several million Euros from the Gilde IT Fund.

But despite being a baby company, the startup has some very grownup experience in R&D. Three of the five founders are PhDs, who have been developing the skills for doing integration in indium phosphide over the past five years. In fact, the CTO, Chrétien Herben, claims to have made the world's smallest integrated DWDM (dense wavelength-division multiplexing) crossconnect to date, measuring just 1.5 by 3.3 millimetres. There's a picture of the four-channel 2x2 crossconnect chip on the home page of the startup's Website.

Herben says the reason he knows his device is the world's smallest is because very few people are doing high-level integration with indium phosphide -- he only knows of one, and that's Lucent Technologies Inc. (NYSE: LU).

Optical circuits made from indium phosphide are more compact than those made in other materials like glass or polymer -- typically they're ten to 100 times smaller. In his first attempt, Herben made a chip measuring 10 by 10 mm. He then improved the design of the individual components on the chip to shrink the chip further.

Since the chip is so small, the process yield is greatly improved, he notes.

But that's not the only reason for wanting to work with indium phosphide. It has three other big attractions. First, it's active, so it's possible to build lasers and amplifiers on the same chip as passive components. Second, it's electro-optic, which makes it possible to create modulators as well. Third, it's fast, with nanosecond response times.

Gary Bjorklund, CTO of Nanovation Technologies Inc. describes indium phosphide as a "wonder material."

But Nanovation has a cautionary tale about indium phosphide. It started out with similar aims to ThreeFive Photonics, but the technology hit some snags. "We made a 2x2 switch that could switch in nanoseconds, but the insertion loss was a factor of 2dB higher [than competing technologies]," says Bjorklund. Potential customers didn't think that was acceptable, he says. As a result, the company was forced back to the drawing board (see Nanovation Comes Down to Earth).

ThreeFive's Herben acknowledges that the losses of his 2x2 crossconnect, and indium phosphide components in general, are indeed too high for commercial application. "But it's possible to compensate for the losses by integrating semiconductor optical amplifiers (SOAs) into the device," he adds.

In principle, it should be straightforward to integrate the extra SOAs. In fact, ThreeFive's founders say they have already made a multiwavelength laser, which integrates multiple SOAs with an arrayed waveguide grating (AWG). The real challenge for the startup will be seeing whether it can make a product at a price and performance point that customers will want to buy.

— Pauline Rigby, senior editor, Light Reading http://www.lightreading.com

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