This course addresses two key aspects of high energy lasers (HEL) for directed energy weapons (DEW). The first is the HEL source configuration and the other deals with the physical processes that affect the propagation of the HEL beam in realistic atmospheres.
There are a number of HEL configurations under development. These include solid-state, gas, free-electron and fiber lasers, among others. For DEW applications, 100’s kWs, CW power levels and multi-km propagation ranges are necessary. One approach to achieving the necessary power levels is to combine a large number of kW-class lasers. Efforts to combine fiber lasers coherently or spectrally have produced ~500 W of average power. A new configuration based on incoherent combining of high-power fiber lasers which can, in the near term, lead to a compact, robust, low-maintenance and long-lifetime, multi-kilowatt HEL system will be dicussed. An important advantage of incoherently combing fiber lasers is that phase locking or polarization control are not necessary. A conceptual design of an incoherently combined HEL system that can deliver 100 kW of CW power on a target of area 100 cm2 at a range of over 5 km is presented. This configuration is scalable to higher CW powers and longer ranges. The other objective of this course is to discuss the optimum laser wavelength and power for efficient propagation in various atmospheric environments, i.e., maritime, continental, urban, etc. The processes which contribute to laser beam spreading and intensity loss include: thermal blooming, turbulence, aerosol/molecular scattering and absorption, aerosol heating/vaporization, and laser beam quality effects. Aerosols, which consist of water, sea salt, organic matter, dust, soot, biomass smoke, urban pollutants, etc, are of particular importance because they result in laser scattering, absorption and enhanced thermal blooming. HELCAP (High Energy Laser Code for Atmospheric Propagation) is a fully 3-D, time dependent code that is suitable for studying and characterizing the atmospheric propagation of HEL beams. The course will also address issues of adaptive optics relevant to the propagation of high energy laser beams. Though it is a critical technology for any laser system, adaptive optics has both fundamental and technological limitations which will be discussed. Intended Audience: This course is intended to present an overview of the various physical processes which affect the propagation of HEL laser pulses in the atmosphere. Scientists, engineers and program managers will benefit from this course. Instructor Biography: Dr. Phillip Sprangle is Chief Scientist and Head of the Beam Physics Branch at the Naval Research Laboratory. He received his Ph.D. in Applied Physics at Cornell University in 1973. His research areas include atmospheric laser propagation, free electron lasers, nonlinear optics and laser acceleration physics. Dr. Sprangle is a fellow of the American Physical Society, DEPS, and the IEEE. He is winner of the International Free Electron Laser Prize (1991), E.O. Hulburt Science and Engineering Award (1986) and Sigma Xi Pure Science Award (1994). Dr. Sprangle has published over 200 refereed scientific articles and holds 12 U.S. patents. Course 4. Beam Combining and Atmospheric Propagation of HELs for DE Applications Classification: Unclassified Instructor: Dr. Phillip Sprangle, Naval Research Laboratory Duration: Half-day course, starts at 0800 CEUs awarded: 0.35 http://www.deps.org/DEPSpages/DEsymp06ShortCourse.html#Class11 -- You received this message because you are subscribed to the Google Groups "Hum Sufferers" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/hum-sufferers?hl=en.
