SPECTROSCOPIC PROPERTIES OF CR4+LU3AL5O12

We report on the near-infrared absorption, emission, and lifetime data of Cr4+:Lu3Al5O12 (Cr:LAG) and compare the results with the known las er material Cr4+-doped Y3Al5O12 (Cr:YAG). Lu3Al5O12 has a smaller unit cell than Y3Al5O12, and this feature is reflected in its spectroscopi c properties. The low-temperature luminescence spectrum is shifted by 85 cm-1 to higher energy compared with Cr:YAG. The luminescence lifeti me of Cr:LAG at 10 K is 28.7 mus (Cr:YAG, 30.6 mus) and at 300 KU is 4 .3 mus (Cr:YAG, 3.5 mus). From these lifetimes we postulate that the q uantum efficiency in Cr:LAG is higher than in Cr:YAG. We discuss the p otential of Cr:LAG as a tunable near-infrared laser.