Eyesafer Fiber Laser Technology for Shipboard Defense

In the Phase II work, we propose to examine near-resonant pumping of Tm:silica fibers with a goal of developing a design for a 20-kW, diffraction-limited, 2040-nm Tm:fiber laser. The design will attempt to counter both thermal effects and nonlinear-optical limits set by Raman or Brillouin scattering. We will support our design work with experimental studies of the fundamental properties of Tm-doped silica fibers, in particular, absorption in the long-wavelength region beyond 1900-nm, where we would pump the final laser stage. Within the resource limits of a Phase II program, we would design and construct a sub-scale fiber-laser system to test and refine our resonant-pumping design. An additional Phase II effort would be to conduct experiments to better understand the thermal limits set by the fiber polymer coating. This continues to be important because in the proposed design the pump laser would still employ a polymer optical cladding to achieve high numerical aperture for 790-nm, diode-laser pumping. One result of the proposed work will be a design for a 20-kW Tm:fiber laser, which could be actualized through follow-on funding. In addition, the data and analysis produced will be of general use for a variety of high-power Tm:fiber lasers.