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The Defense Intelligence Agency produced this reference document, dated 31 March 2010, under its Advanced Aerospace Weapon System Applications (AAWSA) Program. It reviews the state of the art and likely evolution of high-energy laser weapons, including chemical, solid-state, fiber and free-electron lasers, as well as beam control and the history of DoD laser research. It concludes that electrically powered lasers could make megawatt-class weapons practical and that spacecraft laser weapons are conceivable within 20 years. It also recommends ways to protect spacecraft from laser damage.
UNCLASSIFIED/ ;'f81il 8ffllilsl1k WE&i Si'llk>C 25 to 50 fibers have been combined into an even larger fiber with a resultant output power of 50 kW and an effective beam quality of about 30. Highly reliable commercial welders and cutters are made today with fiber lasers which combine beams by splicing laser fibers together to increase output power. Some of these devices operate at a reported wall plug to light-out efficiency > 30 percent but these numbers do not include any power required for cooling. As a weapon, these off-the-shelf lasers could produce useful beams for short distances. A significant advantage of fiber lasers is their inherent ruggedness when compared to slab or rod lasers. Most of the optical functions (such as wavelength and polarization control, beam splitters and combiners) which are required to produce a high-power beam with good beam quality can be integrated into the fibers while slab laser systems require discrete components which must be kept clean and held in mechanical alignment. Given the immaturity and rate of advance of fiber lasers today, it is impossible to predict where they will go. Current power scaling research has been centered on Yb:YAG and Nd:YAG fibers at 1 μm with limited effort at 1.5 ~tm and 2 μm. Although lagging the maturity of 1 μm fibers, they offer potential for increased eye safety. If the maturation process continues as it has, fiber lasers will offer the best promise for high power and good beam quality with inherent ruggedness and reliability. Militarized devices at the 50 kW to 100 kW should be available within the next 15 years and it's not difficult to imagine MW systems within 20 to 30 years. ULTRA-SHORT PULSE LASERS Ultra-Short Pulse (USP) lasers, sometimes called femtosecond (fs) lasers, produce pulses of light shorter than 1 picosecond (10 12 second). Some USP lasers have produced pulses less than 10 fs which is a length of 3 microns and equivalent to only a few cycles of visible light (by comparison, a human hair is about 100 microns in diameter). They were developed in the 1970s using long pulse lasers to illuminate chemical dyes which then produced the short pulses; today USP lasers employ slabs such as Titanium:Sapphire or a variety of fibers and table-top size devices are commercially available. Although the average power of these devices is typically sub- watt, the short pulses result in peak powers which can range from a terawatt (10 12 watts) to a petawatt (10 15 watts). The extremely high power contained in very short pulses has proven useful for precision machining, drilling tiny holes, and selective material removal in a wide variety of materials. In addition to commercial machining applications, medical uses such as eye surgery and cancer cell destruction have been developed. When propagated in the atmosphere, these ultra short pulses do not obey the usual laws of diffraction spreading and can (under certain circumstances) remain tightly focused over long distances. This technology remains in its infancy and research is ongoing to increase average power (generally with a higher pulse rate), to better understand the physics of USP propagation, and to explore material interactions with USP. Much of the USP research today is found in world-wide academic institutions. Other than the potential for inflicting sensor damage, the military potential of these devices is yet to be determined. 10 UNCLASSIFIED/ ,<EiSi'A: QFFI@Itllt ~:!E! enc I
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 31 pages are in the text index: search them above, or from the library's search.