tEchnology sUpEr lAsErs
The HiPER team is keeping a close eye on the
A fusion power plant such as the European hipEr project will need hundreds of millions of laser diode bars Image courtesy of HiPER
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levels,’ he says. ‘Our business is strong with our existing customers and markets, and the demand for fusion-scaled investment is not yet there. We are waiting for the start signal. The technical start signal will be break-even at NIF – but the economical start signal for us will be a customer, with funding, who has an order for a large quantity of laser diodes or a contract for infrastructure development.’ One project that could contribute to creating
this demand is the HiLASE project, based in the Czech Republic. This initiative, which starts in April and has four years’ funding, aims to develop a high-power DPSSL for applications including laser fusion. The organisers will work closely with major European research leaders in this field. The aim is to develop a 100J laser with a 10Hz
repetition rate – the requirement for the first phase of the HiPER power plant. While there are several projects around the world trying to achieve the same goal, project manager Tomáš Mocek believes HiLASE is starting at exactly the right time. He tells Electro Optics: ‘We can learn from projects such as the Mercury laser at LLNL and use new
technology to develop advanced schemes for DPSSLs.’
Unlike LLNL’s Mercury laser based on Yb:SFAP, the HiLASE project will use cryogenic cooling to cool the amplifier in order to increase its efficiency. The HiLASE project also plans to investigate new and different materials for the amplifier, in contrast to the Nd:glass that will be used by researchers at the LLNL in the next generation of high-power DPSSLs. Using the thin-disk technology, Mocek and his colleagues plan to generate picosecond laser pulses at 1-3kHz, with a total power of 1kW. By combining the concepts of large aperture regenerative amplifiers and Yb:YAG thin disk lasers, a system for generation of 2-3ps pulses with energy of 1-10J at 100Hz will be developed. ‘It is a very ambitious project, but still feasible,’ said Mocek. ‘It took the Mercury project seven years to achieve around 60J, whereas we plan to achieve 100J in four years. Our approach also needs to be scalable to the kilojoule level.’
HiLASE project. According to Mike Tyldesley, HiPER project engineer: ‘Given its timescale, HiLASE is occurring at the right time to add impetus to the effort. It is an important project, which will accelerate the development of DPSSLs.’ Tyldesley believes the biggest issues for a high-power repetition rate laser are the gain media, adaptive mirrors, control system, frequency conversion crystals and high-damage optical coatings. ‘For a smaller high-repetition rate laser, most of these exist or are able to be adapted from current technology,’ he said. ‘As the beams become larger, we must step up the size of elements. For gain media, as an example, this is possible with technology existing in Japan. The intent of HiPER would be to grow and educate the photonics industry in Europe so that larger items could be purchased within the EU.’ Tyldesley and his colleagues at the Central
there is a very real concern that
Dpssls of the right power and the appropriate repetition rate will not be
available when we need them John Parris, HiPER
Laser Facility, Rutherford Appleton Labs in the UK are working on their own high-power DPSSL called DiPOLE. Like HiLASE, DiPOLE is based on Yb:YAG, operated at cryogenic temperatures. ‘We are constructing a small-scale prototype of this concept which is almost complete,’ says Tyldesley. ‘Demonstration of laser operation, delivering 10J pulses at 10Hz is expected within six months. If our prototype laser performs as expected, we are confident that the concept can be scaled to
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