Neodymium Nd3 Laser Four-Level Lasers

Solid-state lasers using substitutional neodymium (Nd3+ ions) as the active defects are widely available. Practical lasers contain about 1% Nd3+ dopant. The most common host materials are glass, yttrium aluminum garnet (YAG), Y3A15012, and calcium tungstate, CaW04. In the crystalline host structures, the defects responsible for amplification are NdY and Ndca- 

The important transitions taking place in Nd3+ ion lasers are between energy levels derived from electrons in the / orbitals. The /-electron levels are rather sharp 

At higher Nd3+ concentrations the lifetime of the 4F upper state drops from about 200 ps in a typically 1 % doped material to about 5 ps at higher dopant concentrations. This is due to Nd-Nd defect interactions and associated changes in lattice vibration characteristics. Under these conditions, laser operation is no longer possible. 

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