Plasma Physics Seminar ( Phys 769)

Dr. Phillip Sprangle, Plasma Physics Division, NRL

Atmospheric Propagation of Incoherently Combined Fiber Lasers for Power Beaming Applications

The NRL high-energy fiber laser program is developing a robust, compact, highly effic ient, long-range laser system. The laser system under development is based on the in coherent combining of high-power, single-mode fiber lasers. A key component of this laser program is the development of a multiple fiber laser beam director which is cap able of handling high average power. The unique characteristics of this laser system make it ideal for tactical directed energy and power beaming applications. Presently, the NRL program has 4 fiber lasers with a total cw power of 6.2 kW. The first incoherently combined fiber laser propagation experiments took place at the end of 2007 at NSWC, Dahlgren, VA. The propagation range was 1.2 km, the laser spot size on target was ~ 4 cm and the propagation efficiency was greater than 90% at 3 kW of cw power . These experimental results were in excellent agreement with our modeling and simulations using the code HELCAP [1]. New experiments are underway at the Starfire Optical Range in Kirtland Air Force Base. To date, these field experiments have achieved a propagation efficiency in excess of 80% with a laser spot size on target of ~ 4 cm and transmitted laser power of 4.6 kW at a range of 3.2 km. A comparison between experimental results and our physics modeling will be presented [1]. Incoherent combining of single-mode fiber lasers may have important applications in the area of power beaming to UAVs and low-orbit satellites. The atmospheric propagation and photovoltaic conversion of laser energy for power beaming will be discussed.

[1] IEEE Journal of Quantum Electronics, No.1, January 2009

Acknowledgements: This work was sponsored by ONR, JTO, and NRL.

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