Fiber Lasers Mean Ray Guns Are Coming

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July 30, 2018 | Originally published by Date Line: July 30 on

The U.S. Navy’s most advanced laser weapon looks like a pricey amateur telescope. As it emerges from a chassis high on the USS Ponce to look out onto the daytime sky above the Persian Gulf, its operator sits in a darkened room elsewhere on the ship holding what looks like a game controller. The screen before him is showing a small boat floating near the Ponce, carrying a dark object. The infrared beam hitting the object is invisible, but you can see one spot grow brighter until the object suddenly explodes, sending metal shards spiraling into the water.

This weapon, cobbled together from a half-dozen industrial cutting and welding lasers to produce a total power of only 30 kilowatts, was hardly the megawatt monster military scientists dreamed of decades ago to shoot down ICBMs. But it’s a major milestone, advocates say, toward a future in which directed-energy weapons are deployed in real military engagements. Such a future, they add, will come from changes in mission and in technology. The mission shift has been going on for years, from global defense against nuclear-armed “rogue states” to local defense against insurgents. The technology shift has been more abrupt, toward the hot new solid-state technology of optical-fiber lasers. These are the basis of a fast-growing US $2 billion industry that has reengineered the raw materials of global telecommunications to cut and weld metals, and it is now being scaled to even higher power with devastating effect.

Pentagon officials think the technology for high-energy lasers, like the one tested on the now-decommissioned Ponce, can serve a variety of roles on land and at sea: zapping the cheap rockets, artillery, drones, and small boats loaded with weapons that insurgents have deployed in places like Iraq and Afghanistan. Today, destroying an insurgent rocket costing around a thousand dollars can require a tech-laden Patriot interceptor costing $2 million to $3 million. By comparison, a laser shot from a fiber-laser weapon would cost only $1 in diesel fuel, officials claim.

The High Energy Laser Joint Technology Office (HEL-JTO) was launched to develop solid-state laser weapons. These systems, using slabs of glass or crystal, reached their peak in March 2009 with a Northrop Grumman demonstrator. It delivered a steady 105-kW beam for a full 5 minutes. [See “Ray Guns Get Real,” IEEE Spectrum, July 2009.] The laser didn’t require special fuels or produce toxic gases, but it weighed 7 metric tons and occupied 10.8 cubic meters—about the volume of a large cement truck.

HEL-JTO programs, the Robust Electric Laser Initiative, managed to do it. With a mandate to develop solid-state lasers that were better suited for the battlefield, HEL-JTO set itself a goal of building a 100-kW laser that occupied about 1.2 cubic meters and could generate more than 150 watts per kilogram, operating at 30 percent efficiency or better. Two of the four projects HEL-JTO launched considered new variations on a hot technology for laser machine tools: fiber lasers.

The accomplishments in efficiency, thermal management of waste heat, and beam quality and control using fiber laser technology are impressive and have allowed development of laser weapon systems with reduced size, weight, and power (SWaP) requirements that produce laser power levels approaching the goals for truly effective system.  However, the ability to disable or destroy some objects over a test range won’t be enough to earn laser weapons a place in the arsenal. It has taken the military almost 60 years to get to the point where lasers look like they might actually be useful in combat. But the Pentagon is full of military brass who grew up with “kinetic weapons”—guns and rockets—and must be thoroughly convinced that the age of Buck Rogers has really arrived. Without such widespread support, there won’t be money for the hard and expensive work of deploying a radically new weapon. As one wag put it famously (and in a completely different context), “No bucks, no Buck Rogers.”