Rare earths in lasers

The neodymium laser is popular because it is a solid state laser. Trivalent neodymium ions are incorporated in a host crystal or glass, at about one atomic percent doping. In the solid state, high concentrations of ions are available as opposed to the gaseous state. Further the host crystal provides mechanical strength and chemical inertness. 

The rare elements are suited for incorporation into crystals or glasses as active lasers due to their electronic configuration. The outer most electrons of the rare earths form a complete 

MODERN ASPECTS OF RARE EARTHS AND THEIR COMPLEXES 

Electronic configuration of some rare earth ions. 

The trivalent neodymium ion is a good example of a four-level laser system. The trivalent Nd3+ system is illustrated in Fig. 12.12 in a schematic fashion. 

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