UK tech behind 1GW laser amplifier

The UK’s Centre for Advanced Laser Technology and Applications (CALTA) has supplied a £2.2m gigawatt laser amplifier to the Czech Republic’s Institute of Physics (IoP) for the European Extreme Light Infrastructure (ELI) ‘Beamlines’ facility.

Oxfordshire-based CALTA is part of the Science and Technology Facilities Council (STFC), and exploits technology developed in STFC’s Central Laser Facility (CLF) for industry and big laser facilities.

“The laser platform will benefit new build laser infrastructure projects, including ELI, and will drive new laser-based applications in industry, including advanced material treatments and energy production,” said CLF director Professor John Collier.

The ELI laser amplifier head is based ‘DiPOLE’ – high-repetition-rate super-power pulse laser technology from CLF – and can supply 10J nanosecond pulses at 10Hz. Average power is 100W. Pulses from 2 to 10ns are available, peaking at 1GW at 10ns.

“Each laser burst has power equivalent to that of a full-sized power station,” said STFC.

“DiPOLE technology not only enables high power laser operation at high repetition rates of many pulses per second” said CLF’s Collier, “but also demonstrates high efficiency operation, with at least 10% efficiency in producing laser power from electricity, compared to conventional systems that are typically much less than 1%.”

The amplifier (see photo) will sit part way along an infra-red laser chain. Inside, a doped YAG ceramic block absorbs 10J of pump laser energy over 1ms, CALTA manager Justin Greenhalgh told Electronics Weekly, then releases it at the command of a different frequency 10ns 100mJ trigger pulse from a Czech-made diode laser. Mirrors on the ceramic block zig-zag the trigger pulse six times to allow it to grow into the output pulse.

In the photo, the circular beam splitters reflect at the pump wavelength, allowing energy from pump lasers A and B to directed into the hidden YAG ceramic prism through windows. Transparent at the trigger/output frequency, the splitters allow the trigger pulse to enter and the output pulse to leave through the same windows in a straight line. Cooling helium enters through the top port (capped in the photo).

The resulting 1GW pulse can be used to pump another amplifier which, when triggered by a picosecond pulse, will deliver a petawatt picosecond pulse.

The laser head is the first major contract of its kind between CALTA and IoP.

ELI Beamlines will have four giant lasers delivering petawatt pulses at 10Hz – something that CLF’s venerable Vulcan laser can only do every 20 minutes.

Focused intensities of around 10²³W/cm² will be available.

“Being able to operate high power lasers at high repetition rate is key to developing applications such as medical imaging and radiotherapy for industrial use,” said STFC.

ELI is split between four sites – with Beamlines in the Czech Republic, and others in Hungary, Romania, and one to be decided.

Investment exceeds E850m, mostly from European regional development funds.