YAG  (NEODYMIUM)  LASERS

        Although it should be called a neodymium laser since the active lasing ion is the rare-earth metal Nd³⁺‏, this laser is usually named after the host material, so it is often called a YAG or glass laser, depending on the host (I suppose this makes as much sense as calling the ruby laser an aluminum oxide laser, but it is, indeed,  standard). While many host materials may be used for the ion (with new ones appearing all the time), all of these lasers operate in a similar manner, so the term YAG will be used to describe a generic neodymium laser in this chapter; keep in mind that other hosts exist.

             Used originally as a replacement for the ruby laser in many applications, YAG lasers feature much higher efficiencies than ruby does, have lower pumping thresholds, and can oscillate in CW mode. Traditionally pumped by either a flash lamp or, more commonly, a CW arc lamp, these lasers are pumped most efficiently by semiconductor diode lasers. Having separate cavity optics, SHG crystals can be inserted into the cavity to produce powerful output in the green, for many applications replacing the argon laser as a powerful source of green light. The laser can be Q-switched, making it useful for many materials-processing applications.

TABLE 1.1. Common Nd³⁺ Hosts and Wavelengths