CHARACTERIZATION AND CONTROL OF GAMMA-RADIATION AND PROTON-RADIATION EFFECTS ON THE PERFORMANCE OF ND-YAG AND ND-YLF LASERS

The laser performance of Nd:YAG and Nd:YLF crystals longitudinally pum ped at 800 nm was evaluated before and after exposure to Co-60 gamma r ays and high energy (30-50 MeV) protons, Both forms of radiation creat ed the same damage centers in the respective crystals, which reduced o ptical output primarily by absorbing the laser emission. While the rad iation induced loss at the lasing wavelength for high quality Nd:YAG r eached a limiting value of similar to 0.015 cm(-1) at 100 krad exposur e levels, the loss in Nd:YLF was significantly larger than in Nd:YAG f or all comparable dosage levels, and did hot appear to have a limiting value, Given the relatively short path lengths of the laser crystals that were tested, the loss could be overcome for both materials under pulse-pumped operation, demonstrating that certain Nd lasers can be ef fectively radiation hard by design. Additionally, for the first time, Cr3+ was codoped with Nd in YAG (with minimal Cr4+ formation) yielding a high performance material with a significantly reduced in radiation susceptibility.