Infrared‐Pumped Visible Laser

Infrared‐pumped stimulated emission near 6700 A in BaY2F8 : Yb3+–Er3+ and at 5515 A in BaY2F8 : Yb3+–Ho3+ is reported. In BaY2F8 : Yb3+–Er3+, oscillation takes place at 77 °K in Er3+ transitions from 4F9/2 to the highest level of the ground state at 410 cm−1. Pumping of Er3+ results predominantly from up‐conversion produced by successive energy transfers from Yb3+; direct pumping of the metastable state and higher‐lying states of Er3+ is substantially less effective than up‐conversion. Oscillation in Ho3+ occurs in a transition from 5S2 to the highest level of the ground manifold at 385 cm−1. Up‐conversion and direct pumping contribute about equally to the inversion.