July 06, 2011

High Energy Lasers getting ten times smaller and direct diode lasers

1. The goal of DARPA’s High-Energy Liquid Laser Area Defense System (HELLADS) is to develop a 150 kilowatt (kW) laser weapon system that is ten times smaller and lighter than current lasers of similar power, enabling integration onto tactical aircraft to defend against and defeat ground threats. DARPA recently completed laboratory testing of a fundamental building block for HELLADS, a single laser module that successfully demonstrated the ability to achieve high power and beam quality from a significantly lighter and smaller laser.

The program now enters the final development phase where a second laser module will be built and combined with the first module to generate 150 kW of power. The goal is to have the 150 kW laser completed by the end of 2012.

Following the final development phase, plans call for the laser to be transported to White Sands Missile Range in the early-2013 timeframe for ground testing against rockets, mortars, surface-to-air missiles and to conduct simulated air-to-ground offensive missions.

2. Teradiode is startup that is developing new direct diode lasers

Combining the Advantages of Wavelength beam combining (WBC) and Direct-Diode Lasers

There are three generally accepted approaches to increasing the brightness of direct-diode lasers:

* Side-by-side beam combining
* Coherent beam combining (CBC)
* Wavelength beam combining (WBC)

Only WBC has the necessary qualities to be adapted for use in a high brightness industrial laser. Side-by-side beam combining increases output power in proportion to the number of emitters, but decreases beam quality by the same proportion. As a result, brightness can’t be increased. Coherent beam combining demands active phase locking of all emitters such that the optical path length difference between emitters is λ/10 or better. Little progress has been made in scaling CBC beyond several watts, despite substantial investment, so CBC is not considered a practical pathway to a high-brightness industrial laser at this time.

A direct-diode laser using TeraDrive™ technology has all the advantages of WBC, including: ultra-high spatial brightness, power scaling, high spectral brightness, wavelength stability and wavelength selectability. It also preserves the advantages of direct-diode lasers, including high efficiency and high reliability.

Ultra-high spatial brightness. TeraDiode’s fiber-coupled prototypes have demonstrated output power of more than 1 kW with a BPP of 18 mm-mrad, equal to a brightness of 31 MW/cm2/sr. This is about ten times brighter than commercially available 1 kW direct-diode lasers. Our kilowatt class direct-diode lasers for metal processing, scheduled for launch in the second half of 2011, will deliver brightness of 1,000 MW/cm2/sr, which equals or exceeds that of comparable fiber lasers.

Power scaling. The maximum power available from a resonator using TeraDrive™ technology is limited only by thermal considerations. TeraDiode is developing lasers that range from several watts powered by a few single emitters, to several kilowatts powered by an array of diode bars. For directed energy weapons, the company has charted a development pathway that leads to a nearly diffraction limited, free-space 100 kW system.

TeraDiode has developed the first ultra-high brightness, direct-diode lasers that are bright enough to cut and weld metal. They combine unprecedented brightness with efficiency, reliability and low cost. At TeraDiode, we believe that direct-diode lasers using TeraDrive™ technology will, in time, replace fiber, disk and other lasers for the most demanding material processing applications.

TeraDiode envisions selling lasers “compact enough to be deployable on a tank or ship,” Sossen says, that could be used to disable enemy UAVs (unmanned aerial vehicles) or even blow up incoming rockets or artillery shells.

That’s still more than five years away, though. In the nearer term, TeraDiode is looking to deploy the world’s most advanced deterrent to heat-seeking missiles, Sossen says. Here’s how it works. The company’s laser system could be mounted on the back of a fighter plane’s fuselage. If a missile is launched at the plane, the laser would deliver a dazzling enough burst of infrared light to confuse the seeker head so it can’t home in on the target. (It might also destroy the missile, but that presumably would require a more powerful beam.) Field testing for this airborne system could begin in about a year, Sossen says, with full deployment in three to five years, if all goes well.

There are plenty of other near-term military applications as well, he says—things like illuminating targets (which is typically done so they can be photographed or shot at) from great distances via a laser that is handheld or mounted on a jeep, helicopter, or UAV.

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