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Research & Development

Fiber focus for new petawatt laser design

05 Mar 2015

Thales collaborates with leading research group at École Polytechnique on new coherent amplification network approach to high-power systems.

Updated* The optronics division of French defense giant Thales and researchers at École Polytechnique in Paris are working together on a radical new approach to building giant lasers capable of producing petawatt pulses at unprecedented repetition rates.

Their collaboration, part of an ongoing partnership signed by the two organizations a year ago, is known as “X-CAN”, short for coherent amplifier network. Building on a concept developed by the highly regarded academic group, and featuring chirped-pulse amplification (CPA) pioneer Gérard Mourou among others, the approach is based around fiber lasers, rather than the more traditional Ti:sapphire amplifier chains used in such systems.

One of the big advantages of using fibers is that they are far more energy-efficient than Ti:sapphire lasers, although it is more difficult to get them to emit ultrashort pulses with the kind of energy needed for petawatt-class installations.

According to a September 2014 presentation authored by some of the researchers leading the collaboration, an X-CAN demonstrator system based on ytterbium-doped fibers featuring 91 coherently combined channels could operate with a wall-plug efficiency as high as 30 per cent.

But the number of channels could be increased dramatically, to perhaps more than 1000, to deliver extremely high-power pulses at a repetition rate as high as 10 kHz - four orders of magnitude faster than the current state-of-the-art.

The idea builds on earlier work by the International Coherent Amplification Network (ICAN) consortium, which features dozens of world-leading laser laboratories. Funded partly by the European Commission under Framework Programme 7, the ICAN feasibility study’s main result was a design brief for modular high-power laser systems that could potentially replace traditional sources of X-rays, gamma rays and ions used in synchrotrons and particle accelerators.

Industrial potential
But it is hoped that there will be numerous spin-off applications beyond that of particle physics. In their joint announcement on the X-CAN development agreement, which was officially signed off in early February, Thales and École Polytechnique said:

“These innovations in laser technology will open up new avenues of scientific research and ultimately offer numerous practical applications including the transmutation of nuclear waste, proton therapy and isotope production for nuclear pharmacology, as well as design solutions for sub-critical nuclear reactors and even ways to clean up orbital debris in space.”

In their final report on the ICAN feasibility study, the project team wrote: “What has become very clear during the project is that ICAN lasers are not just appropriate for laser wake field acceleration experiments.

“A host of applications both from within the particle physics community and also from many other areas of physics and technology will become viable with the development of ICAN.”

Specifically, they say that the ability to create high average power femtosecond-pulse systems using a scalable, modular, approach will result in widespread industrial applications.

“All of the applications, and the eventual success of ICAN, are based on the two key factors that the ICAN source provides – high average power, and high efficiency.”

The development should also benefit the local network of photonics institutes and companies in Palaiseau, which includes L’Institut d’Optique – site of a joint research laboratory focused on diode-pumped ultrafast lasers that was set up with Bordeaux-based Amplitude Systèmes.

École Polytechnique president Jacques Biot said: “Our collaboration with Thales on X-Can is a perfect example of our ambition to create research initiatives in a collaborative way in selected scientific areas. It also illustrates the potential of the Paris Saclay cluster to enhance cooperation among its members."

Thales told optics.org: "[The] existing state-of-the-art for petawatt lasers is BELLA [the Berkeley Lab Laser Accelerator], which has a repetition rate of 1 Hz and a wallplug efficiency of 0.03 per cent.

"The goal of the X-CAN concept will be to produce a petawatt-class laser with a repetition rate of 10 kHz and a wallplug efficiency of 30 per cent, i.e. an increase of three orders of magnitude for efficiency and four orders of magnitude for the repetition rate."

* Updated (March 10th) to include additional information on pulse repetition rates from Thales.

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