Posted: December 27, 2007

EU-funded Uranus project showcases advances in fiber lasers

(Nanowerk News) A new generation of ultrafast fiber lasers being developed in Europe is creating more uses for the beams of high-intensity light, while lowering production and maintenance costs and increasing efficiency.
To date, many commercial ultrafast lasers have been based on solid-state technology using bulk optical components. However, they have several drawbacks, not least their large size and high production and maintenance costs--problems that can be solved by using optical fiber, rather than air, to carry the light.
"Fiber lasers could replace solid-state lasers for most uses, as well as open the door to new applications," explains Mircea Guina, a researcher at the Tampere University of Technology in Finland.
Guina, the manager of the EU-funded Uranus project, foresees ultrafast fiber lasers playing a key role in machining even smaller nanotechnology systems and in demonstrating practical new applications such as optical coherence tomography, among many other applications.
"There are literally hundreds of uses," he says.
The Uranus project has been fundamental in advancing the technology in Europe, allowing partner companies such as laser manufacturers Fianium and Corelase to take a leading role in the sector, and strengthening the position of Stratophase and NKT as suppliers of nonlinear crystals and photonic crystal fibres, respectively.
"The technology and the sector today are incomparable to what they were like four years ago," Guina notes.
Broadly, the Uranus researchers' two main goals were to develop ultrafast laser systems operating at different wavelengths, and to develop and test broadband fiber sources. They achieved both goals, and even surpassed their own expectations.
"Our research broke new ground ? the number of research papers we published is proof of that," Guina says. Uranus' achievements include the first-ever demonstration of a mode-locked laser that uses a ytterbium-doped photonic bandgap fiber as both a medium and method of compensating beam dispersion. This discovery contributed to the development of the first supercontinuum fiber laser being sold as a ready-to-go system by Fianium.
"The supercontinuum source can generate pulses at all wavelengths," explains Oleg Okhotnikov, coordinator of the Uranus project. "For example, in the case of medical imaging you can select the wavelength you need from the broadband spectrum to detect a specific type of chromophore attached to a cancer cell."
Such new applications are not the only benefit of ultrafast fiber lasers. Compared to solid-state lasers, fiber systems are more efficient, smaller, and cheaper to produce.
"Fiber is more efficient than air at getting the light to its target so it needs less power to achieve the same results as solid-state systems. It is also more stable and robust," Okhotnikov says.
Fiber systems are also considerably cheaper. Though many of the uses for them are new, fiber laser systems have been around for some time. Much of the technology involved was first developed during the 1990s when optical fiber started to be used for communications. Not only does that mean that fibre systems are well tried and tested, it also means that the components, such as the diode pumps that power the laser pulses, are relatively cheap.
"Production costs for a fiber laser are considerably less than for a solid-state system. A fiber 20-W system operating at less than 15 picoseconds costs around ?50,000 compared to the ?150,000 price of a solid-state system," Okhotnikov says.
It is therefore not surprising that increasing numbers of industries requiring lasers are switching to fiber--a boon for the project partners. In the last four years, UK-based Fianium has doubled turnover each year and quadrupled its number of full-time staff, while opening sales offices in Asia and the United States. Meanwhile, Corelase, another Uranus partner and developer of the X-lase high-power fiber laser, was acquired by European application developer Rofin-Sinar in early 2007, due in part to the success of its work in the project.
Since the end of Uranus, the team have presented proposals for new projects in order to continue their research.
"We have come a long way in recent years, but there are still many more areas to explore," Guina says.
Source: LaserFocusWorld
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