The key objective has been to design a scalable architecture, combining multiple kilowatt-class lasers to enable the brightness of the beam to be easily dialled up or down. For robustness the team has chosen to exploit established fibre-laser technologies, originally developed for industrial materials processing, with the biggest challenge having been to find an effective way to combine and control the output from many different fibre-laser amplifiers.
“We need to make sure the power reaches the target, which may be several kilometres away,” says Hoad. “That means we need to steer and point the laser with high precision, while also compensating for the effects of atmospheric turbulence on the propagation of the beam.”
Various technologies could be used to combine the beams, but QinetiQ has opted to pursue an electronic phase-combining technique that allows critical parameters such as the shape, central brightness and spot size of the laser beam to be more precisely controlled. While similar in theory to phased-array radar, the much shorter wavelengths of infrared lasers require greater engineering precision and efficient algorithms to enable accurate and high-speed electronic control.
Physicists at QinetiQ’s R&D campus in Malvern have been charged with perfecting this coherent phase-combining technique. “As well as the physics challenge we now have an engineering challenge to show that our approach can deliver a robust solution in many different environments,” says Hoad. “External factors such as vibration and positional stability will make a huge difference on how well you can control the phasing of the output beam.”
Meanwhile, over at QinetiQ’s Cody Technology Park in Farnborough, efforts are focused on integrating the core phase-control technology with high-power laser sources, as well as alignment optics and a power source. A large systems-integration facility is available for indoor testing, allowing the team to evaluate the effect of the phase control on the output beam.
Longer term, QinetiQ believes that directed-energy systems exploiting either high-energy lasers or high-power radio-frequency transmitters could be used more generally for wireless power transfer. For example, beaming energy at a co-operative target, such as a drone equipped with a receiving system, would make it possible to recharge an onboard power-storage device.
Other possible scenarios include emergency response situations, where power needs to be supplied to critical infrastructure without running cables. The European Space Agency, meanwhile, is also interested in using the technology to beam high-bandwidth data into space. Wireless power-transfer technology could even support the mass-market adoption of electric vehicles, providing top-up charges from systems installed along the motorway. “This research is still very speculative, but it shows the enormous potential of directed-energy technology,” comments Hoad. “It could be really interesting for some applications.”
Developing such high-power systems requires expertise in many different aspects of laser science. One is to understand how the atmosphere affects the propagation of high-energy laser beams, since turbulence close to the ground and changing weather conditions make it challenging to control and target the beam. Laser safety is another crucial area of research, with experts working to evaluate the hazards and risks of firing high-power lasers into the sky, such as understanding what happens when some of the energy is reflected back from the target.
QinetiQ is looking for scientists or engineers who can demonstrate a working knowledge of photonics and laser physics. “We are open minded about the amount of previous experience a candidate can offer, since we provide dedicated training for new recruits to enable them to work with our technology and our facilities,” he says. “New team members have the opportunity to move around the business, so an optical physicist working primarily in Malvern might spend time in Farnborough to see how the technology gets integrated, while our high-energy engineers would go to Malvern to understand how the core technology works.”
QinetiQ is also keen to support staff who wish to further their academic training, whether for an undergraduate university course or a sponsored PhD. Hoad himself joined the business as a technician apprentice, studying part-time to obtain first a Master’s and then a PhD, while several of his team members are currently working towards their doctorates. “We are building stronger links with academia, and sponsoring students is a great way for us to that,” he says.
Candidates who are fresh out of university can also join through QinetiQ’s two-year graduate training scheme, which assigns each new entrant to a “home” business while also offering six-month placements in other departments. “There are plenty of options within QinetiQ for people who are interested in laser science,” says Hoad. “As well as our work on high-energy sources, other groups are focusing on areas such as LIDAR and optical ground systems for communications.
