Radiation-induced defects in lithium yttrium fluoride

Aerospace applications may result in exposing the laser host material LiYF4 to ionizing radiation which may degrade its performance as a host material by introducing loss processes which affect the threshold energy. Ionizing radiation produces a series of partially polarized absorption bands in the UV-visible region of the optical spectrum. Comparison of the optical spectr a obtained after irradiation at 300 and 195 K did not show a difference in the number and spectral location of the absorption bands at 77 K. The absor ption bands observed at 1.96, 2.98, 3.7, and 4.94 eV were found to be polar ized more strongly perpendicular to the c-axis. Other bands at 1.97, 2.3, 2 .85, 3.7, and 4.43 eV were observed to be polarized parallel to the c-axis. Using optical relations and the previously identified F-center band at 3.7 eV, the 2.88 and 4.43 eV bands have been identified as also due to the F-c enter, the 1.97 eV band as due to the M-center, and the 2.3 eV band as due to the R-center.