Highly efficient laser operation of Nd-vanadates under direct pumping into the emitting level

摘要

Highly efficient one-micron laser emission in Nd-doped vanadates under direct pumping into the ~4F_(3/2) emitting level is reported. A 1.0-mm-thick, 1.0-at.% Nd:YVO_4 crystal operated with 80% slope efficiency (79% overall optical-to-optical efficiency) under Ti:Sapphire pumping and 75% slope efficiency versus absorbed power under diode laser pumping at 880 nm. Slope efficiency of 80% (overall optical-to-optical efficiency of 77%) under Ti:Sapphire pumping and 66% with respect to the absorbed power under diode laser pumping at 879 nm is obtained from a 3.0-mm-thick, 1.0-at.% Nd:GdVO_4 crystal. These values, which were superior to those obtained by pumping into the ~4F_(5/2) level, were explained consistently by the effect of the quantum defect between the pump and laser radiation, the superposition of pump and laser mode volumes, the pump level efficiency and the residual optical losses.