Development of Multiply Sensitized Ho:YLF as a Laser Material

The results of a 12 month program to develop multiply sensitized Ho:YLF as a Q-switched laser material are presented. This material is the only material in which efficient laser operation at 2 micrometers has been reported at room temperature. Crystals were grown by the Top-Seeded Solution Technique, a modification of the Czochralski process. Extensive analysis of the effects of feed purity and growth technique on the crystalline quality and damage susceptibility of this material are presented. Extensive spectroscopic measurements are reported with direct observation of sensitization quantum yields of three; the implications for optimization of the material for specific applications are discussed. Q-switched operation of different material compositions is reported (calcite with LiNbO3). The composition 50% Erbium, 6. 7% Thulium, 0.34% Holmium has exhibited a 6.5 joule threshold and a 2.5% slope efficiency. A calculation of the thermal loading at fracture of a uniformly heated rod cooled at the surface is presented. See also report dated Jan 1973, AD755530.