摘要
Ⅰ. INTRODUCTIONAlexandrite is a hopeful laser crystal not only because the sharp R-line shows laser action, as in ruby, but also the vibronic sideband is involved in the lasing of this crystal, in this case the system is of four-levels and is widely tunable （700 nm--800 nm）. We have studied the dynamic properties of the excited states of Cr<sup>3+</sup> in BeAl<sub>2</sub>O<sub>4</sub>. The relaxation of the system within the excited states reveals the dynamics of the interactions of the ion defects with phonons. As the time of relaxation
基金
Project supported by the National Natural Science Foundation of China.
