Infrared-Pumped Visible Laser

Abstract

Infrared‐pumped stimulated emission near 6700 Å in BaY₂F₈ : Yb³⁺–Er³⁺ and at 5515 Å in BaY₂F₈ : Yb³⁺–Ho³⁺ is reported. In BaY₂F₈ : Yb³⁺–Er³⁺, oscillation takes place at 77 °K in Er³⁺ transitions from ⁴F_9/2 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.