120W single frequency laser based on short active double clad tapered fiber

Summary form only given. High-power single-frequency lasers are very attractive for a wide range of applications such as nonlinear conversion, gravitational wave detection, atom trapping or LIDAR. Power scaling in single-frequency regime is a challenging domain of research. In fact, nonlinear effect such as stimulated Brillouin scattering (SBS) is the primary power limitation in single-frequency amplifiers. To mitigate SBS, different well-known techniques have been improved: temperature or strain gradient, gain competition. These techniques allow generation of several hundred of watts [1]. Large mode area (LMA) fibers, transverse acoustically tailored fibers [2], coherent beam combining and also tapered fiber [3] seem to be serious candidates to continue the power scaling. The main goal is to reduce optical densities by using large effective area, leading to an increase of the SBS threshold. By adiabatic transition from few microns to several tens of microns, tapered fibers allow to increase the core diameter fibers while keeping a single mode emission. We report on the generation of stable 120W optical power with diffraction limited output, and narrow linewidth (Δν<;30 kHz).