RING-DOPED CLADDING-PUMPED SINGLE-MODE 3-LEVEL FIBER LASER

We propose and theoretically analyze three-level cladding-pumped fiber lasers in which the laser-active dopant is placed in a ring around a single-mode core. A ring-doped laser can work efficiently at wavelengt hs with strong small-signal absorption. This is otherwise difficult in a cladding-pumped fiber. Moreover, ring doping makes the laser less s ensitive to quenching of the laser-active dopant and to excited-state absorption of the lasing field. In simulations of a Yb3+-doped fiber l aser, ring doping increased the slope efficiency to 62%, up from 13% f or a conventional core-doped fiber. (C) 1998 Optical Society of Americ a.