Efficient laser emission in concentrated Nd laser materials under pumping into the emitting level

The possibility of using concentrated Nd laser materials for efficient laser emission and for scaling to high powers is discussed. It is shown that the increased optical absorption in these materials makes direct pumping into the emitting level feasible, with a reduction of the quantum defect between the pump and emission wavelengths, which in turn can enhance the laser emission characteristics and reduce heat generation under pumping. The investigation of the effect of Nd concentration on emission decay of Nd:YAG indicates that up to quite high concentrations, the reduction of the emission quantum efficiency by self-quenching can be compensated by an increase in the pump absorption. Efficient continuous-wave laser emission is demonstrated under direct pumping into the ⁴F_3/2 emitting level of Nd:YAG crystals with up to 3.5-at.% Nd, Nd:YAG ceramics with up to 6.8-at.% Nd, and Nd:YVO₄ crystals with up to 3-at.% Nd. Superior performance as compared to traditional pumping into the ⁴F _5/2 state were obtained. It is inferred that direct pumping into the emitting level of concentrated Nd materials can improve the efficiency of solid-state lasers in the free-generation or low-storage regimes and opens the possibility of scaling these lasers to high powers