Laser guns are a common sight in science fiction, but until recently they've not been seen on real-world battlefields. That's changing, with many of the world's biggest defence companies developing prototypes for the US military.
Laser weapons work differently to traditional artillery and small arms. Rather than physically penetrating a target, they transmit large amounts of energy - in most cases rapidly heating up the target. That can make missiles explode in mid-air, or cause drones to fail and fall out of the sky.
There are several benefits to lasers over conventional weapons. Firstly, the beam is inaudible and invisible to the naked eye, making it harder to trace the source. Secondly, light is only very slightly affected by gravity.
Thirdly, they require no ammunition - just energy. Finally, they dramatically outrange conventional weapons and even work in space.
Energy levels
Since 2014, the US Navy has been testing a 30-kilowatt laser on the USS Ponce. Lockheed Martin has also just announced a truck-mounted 60-kilowatt laser weapon for testing against small drones and mortars.
These energy levels are relatively low still, but Mark Gunzinger, a senior fellow at the Center for Strategic and Budgetary Assessments, told the AFP that within a few years there'll be prototypes of more than 150 kilowatts. Within six to eight years, the US could be using laser systems of more than 300 kilowatts.
At that level, a laser could knock out an incoming missile with a head-on beam. Though no doubt missile engineers will begin to develop countermeasures - perhaps using graphite or carbon heat shields of the kind used on spacecraft.
Shrinking the technology
The most important next step, however, is shrinking the technology. Physical space limitations on cooling and power production are the biggest barriers to progress, especially on smaller devices like Lockheed's truck-mounted laser.
"For a vehicle like this, there will be some engineering limits," said Jim Murdoch, an international business development director at Lockheed.
"We will run out of space... that's the kind of challenge we are working."
