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A supercontinuum success story

04 Feb 2020 Margaret Harris
A man standing in front of a display showing a laser with a rainbow output and a screen in the background reading
Technology development. Carsten Thomsen, VP for ultrafast lasers at NKT Photonics, shows off the company's supercontinuum laser at Photonics West. (Courtesy: Margaret Harris)

I always enjoy hearing stories about how scientific technologies grow and develop. There’s something fascinating about the way yesterday’s barely-functional prototype morphs into tomorrow’s reliable tool – not least because it doesn’t always work out that way, and when it does, the pathway to success is usually anything but straightforward.

Consider the supercontinuum or “white-light” laser. This apparent contradiction in terms produces a veritable rainbow of spatially coherent light, typically by sending ultrafast pulses of laser light through a nonlinear optical fibre. It has several uses, but the combination of bright light and broad spectrum makes it particularly attractive for biomedical imaging and quality control.

In its early days, though, the supercontinuum laser was – well, a bit of a pain. According to Carsten Thomsen, who led the effort to commercialize the device for use outside specialist research laboratories, the earliest prototypes at his company NKT Photonics only lasted a few hours before the fibre degraded so much that the device became unusable. The reasons for these failures weren’t clear, and when Thomsen and his colleagues began to investigate, they initially weren’t even sure what to look for. At one point, they resorted to setting up a whole room full of supercontinuum lasers – racks and racks of them – and monitoring them as they quietly destroyed themselves. “We needed to understand the physics behind the failure,” Thomsen told audience members at an event organized by the European Photonics Industry Consortium (EPIC) during Photonics West. “Once we understood the physics, we could do improved lifetime testing.”

The answer, it transpired, was that the powerful laser light was creating defects in the glass within the optical fibres. The company solved this problem by purchasing a small materials-science firm and using its expertise to develop better fibre materials. By 2008, these efforts had pushed the laser’s lifetime up to 3000 hours, or about four months of continuous operation. That may not sound like much, but it proved good enough to attract the attention of a microscopy firm, Leica Microsystems. Leica wanted to use supercontinuum lasers to excite fluorophors in biological samples labelled with various dyes, and its involvement proved crucial to commercializing the device. In fact, Thomsen, who is now NKT Photonics’ vice president for ultrafast lasers, told me that his advice for entrepreneurs is always “find someone who will use your product even if it’s not perfect”. A decade or so later, he adds, NKT’s supercontinuum lasers can run continuously for two or three years without failing – although not necessarily at the higher powers that a few of the company’s more industrially-oriented customers would like to access.

I thought about the supercontinuum laser again during a later talk by Eric Aguilar, who is the chief executive and co-founder of a California-based start-up called Omnitron Sensors. He and his colleagues are working on a LiDAR (laser ranging and detection) system for autonomous cars in which the position of the ranging beam is dithered, or quickly shifted around, in a way that mimics the slight but rapid movement of an animal’s eyes. “Humans dynamically compensate for motion using their inner ear,” Aguilar told me. “We want to give this same property to LiDAR.”

Aguilar declined to give further details, and in the Q&A session after his talk, a sceptical audience member challenged him, asking, “How do I know you’re real?” While better LiDAR systems would certainly help autonomous vehicles get better at detecting and avoiding objects, it remains to be seen whether Aguilar’s bio-inspired idea will make it into a practical product. But then, that’s the beauty of stories. You never know how they’re going to end.

Copyright © 2020 by IOP Publishing Ltd and individual contributors