Ruby, spectrum principle

Neodymium and YAG Lasers. The principle of neodymium and YAG lasers is very similar to that of the ruby laser. Neodymium ions (Nd +) are used in place of Cr + and are often distributed in glass rather than in alumina. The light from the neodymium laser has a wavelength of 1060 nm (1.06 xm) it emits in the infrared region of the electromagnetic spectrum. Yttrium (Y) ions in alumina (A) compose a form of the naturally occurring garnet (G), hence the name, YAG laser. Like the ruby laser, the Nd and YAG lasers operate from three- and four-level excited-state processes. 

Mode-locked Nd-glass or ruby lasers have also been used to investigate hole-burning and intramolecular dynamics in molecules, as have intracavity dye laser techniques, which operate on the principle of transferring the loss of intensity at the frequency of the hole in the spectrum into the enhanced gain of a dye laser, whose broadband output overlaps that frequency. 

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