Continuous-wave diode-pumped Yb:glass laser with near 90% slope efficiency

Room temperature highly efficient laser action from an ytterbium-doped phosphate glass is demonstrated when end pumped by a 975nm fiber-coupled laser diode. Laser slope efficiencies as high as 88% have been obtained, leading to pump-to-laser conversion efficiencies greater than 50%. From the analysis of pumping threshold and laser slope efficiencies the authors have determined both the optical losses and emission cross section at laser wavelength (1028nm).