Blue LEDs are commonly surrounded with a cerium-doped matrix of this material, as they together form a phosphor that shifts part of the blue spectrum towards a broad yellow, giving the appearance 3 of white light emission. Most nonplanar ring oscillators use this crystal as a host material. A device using this crystal has some problems when used at its (*) 946 nanometer transition because it's only a three-level gain medium. This crystal is best 
Blue LEDs are commonly surrounded with a cerium-doped matrix of this material, as they together form a phosphor that shifts part of the blue spectrum towards a broad yellow, giving the appearance 3 of white light emission. Most nonplanar ring oscillators use this crystal as a host material. A device using this crystal has some problems when used at its (*) 946 nanometer transition because it's only a three-level gain medium. This crystal is best known for its use as a diode-pumped solid-state laser, emitting at6 1064 nanometers when doped with neodymium. For 10 points, identify this pervasive garnet.
Blue LEDs are commonly surrounded with a cerium-doped matrix of this material, as they together form a phosphor that shifts part of the blue spectrum towards a broad yellow, giving the appearance 3 of white light emission.
YAG [or: yttrium aluminum garnet] 