Active two-dimensional and three-dimensional Reconnaissance, Surveillance and Target Acquisition sensors are being developed by the military to improve its target identification capability. One of the most promising optical sources for this application is a fiber laser operating at the eye-safe wavelength of about 1550 nm and at high pulse repetition rates of 50-1000 kHz. These lasers are based on Er:Yb co-doped fibers of the double clad (DC) design. Currently available Er:Yb DC fibers exhibit pump-to-signal conversion efficiency of about 40%. For Er:Yb DC fibers to be used in fiber lasers for navigation, ranging, identification, etc., the conversion efficiency must be increased beyond the current ceiling of 40%. This proposal deals with increasing the efficiency of Er:Yb DC fibers by: (i) maximizing the P and the Yb concentrations in the fiber gain region, and (ii) decreasing the Yb/Er ratio for fixed Yb concentration by increasing the Er concentration in the gain region. Nufern is an industry leader in the design and fabrication of rare earth doped fibers and has identified a path to develop high efficiency Er:Yb DC fibers. Due to its vast prior experience, Nufern is uniquely qualified to undertake the proposed research and ensure that the program concludes successfully.
Benefits:The proposed work is expected to generate fibers that will enable significant enhancements in pump-to-signal conversion efficiencies. The technology developed by Nufern will facilitate development of eye-safe devices for coherent LIDAR, obstacle avoidance, as well as weapon systems. In addition to these military applications the fibers are expected to spur activity in commercial areas such as free space communications, satellite communications, portable eye-safe industrial lasers and in biomedical applications such as two-photonmicroscopy and monochromatic X-ray generation.
Keywords:Erbium, Ytterbium, Fiber Lasers, Conversion Efficiency, Er:Yb Double Clad Fiber, Pump Absorption, Signal Absorption
