Laser performance of Yb^3+ doped oxyorthosilicates LYSO and GYSO

Ytterbium offers a number of advantages as the active ion in solid-state laser crystals, but is hindered by the disadvantages of a three level lasing scheme. Yb(3+)-doped oxyorthosilicates have emerged in recent years as potentially quasi-four level laser materials. Two such crystals, Yb:GdYSiO(5) and Yb:LuYSiO(5), are investigated to determine the extent of four-level behavior. It is shown that these crystals demonstrate a significant reduction in the pump intensity required to reach threshold, but still exhibit three-level effects in terms of self-absorption, population inversion, and thermal sensitivity. The important material properties such as the coefficient of thermal expansion and the thermo-optic coefficient are measured.