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Revolution in Fiber Lasers (RIFL)
Program Manager: Dr. Joseph Mangano
The RIFL program is developing kilowatt-class, efficient, coherently-combinable fiber laser amplifiers that operate narrowline and with near-diffraction-limited beam quality. These fiber laser amplifiers will enable the development of arrays of fiber amplifiers whose beams can be coherently combined into a single beam to reach very high power. The monolithic all-fiber design approach provides a robust platform that is more rugged than laser systems that employ free-space power transport. Fiber laser amplifiers developed in the RIFL program will find applications in laser communications, target search and track, target identification and IFF, and ultimately high-power laser weapon applications.
The ultra-high efficiency (30%) and near diffraction limited beam quality promised by fiber laser amplifiers can lead to high power laser systems that are more than 10 times lighterweight and more compact than existing high power laser systems currently deployed by the DoD.
The two biggest hurdles that must be overcome for successful demonstration of coherently combinable fiber laser amplifiers are unwanted non-linear effects caused by stimulated Brillouin scattering (SBS) when the fiber laser amplifier is operating at high power and narrow linewidth, and the low brightness of the current generation of laser diode pumps which limits the power that can be efficiently coupled into the cladding of the fiber. Each of the performers has proposed different novel and promising techniques to mitigate the effects of SBS and will devote substantial effort towards developing these techniques. To achieve the necessary efficiencies of the pump lasers, the performers have teamed with suppliers of advanced fiber-coupled laser diode arrays that increase laser diode array brightness and the efficiency with which the laser diode pump power can be coupled to the doped gain medium in the fiber laser amplifier.
Each high power fiber laser will be independently tested and fiber modeling and simulation performed to support early evaluation of the novel fiber laser amplifier designs. Early testing metrics include beam properties such as beam output power, beam quality, integrated phase noise, and polarization, as well as fiber laser amplifier system characteristics, such as architecture, runtime of the laser, lifetime of the system, and system efficiency. Laser performance is calculated by analytical modeling methods coupled with computer solutions of the relevant nonlinear equations and utilization of the beam propagation method to provide detailed evaluation of contractor baseline designs.