Efficient High Power 2 micron Tm3+-Doped Fiber Laser

This proposal is for the development of new Tm3+ doped germanate glass fibers for efficient high power 2 micron fiber lasers capable of generating an output power of up to hundreds watts. We propose to use Tm3+ doped germanate glass fibers because silica glass fiber is not the ideal host for lasers at wavelength of 2 micron and longer. Germanate glass exhibits lower phonon energy compared to silica glass, increasing the quantum efficiency of 3F4 level of Tm3+ ions. Importantly, Tm3+ can be highly doped into germanate glasses, which results in so called cross-relaxation, dramatically improving the quantum efficiency. We will develop double-clad single mode germanate glass fibers with greater than 6wt% Tm3+ concentration to take full advantages of this Tm3+ cross-relaxation process, developing highly efficient fiber lasers at 2 micron. This type of fiber laser is useful for LIDAR applications, can also be used to pump Ho3+-doped crystals to generate extremely high power 2 micron lasers.