Clad-pumped Yb : Er codoped fiber lasers

Double-clad and Yb:Er codoped fiber lasers emitting at eye-safe wavelengths (>1.5 mum) have been investigated by varying the codopant concentrations, core modifiers, fiber length, and the spectrum of the diode pump. With a pr oper composition, the laser output contains only one lasing wavelength, at 1.6 mum. Highest slope efficiency greater than 60% for this three-level sys tem, emitting only at 1.6 mum, has been obtained by using a 20-m-long, doub le-clad and codoped fiber with the core and clad diameters of 6.3 and 300 m um, respectively. By tradeoff of slope efficiency for higher output power, a 30-m-long fiber is considered to be the best choice.