OPTICAL PUMPS FOR LASERS-PHASE II.

The goal of this research program is to achieve efficient optical pumps for lasers. This second phase may be divided into two tasks to fabricate spectral additive lamps which will radiate efficiently in an absorption band or bands of NdYAG, and to demonstrate the efficiency of the lamps in an appropriately designed laser head. During this quarter lamps having either polycrystalline or single crystal Al2O3 sapphire bodies were made and studied spectroscopically. The lamps were filled with amalgams of mercury and either sodium, potassium, rubidium, or cesium. Quartz bodied lamps filled with sodium iodide and mercury were also made. The latter was also tested as a laser pump. Among the Al2O3 bodied lamps the K-Hg one appeared to be the most promising as a pump for NdYAG. From spectroscopic data it was about four times as efficient a radiator at the major absorption bonds of NdYAG compared to a tungsten lamp operating at its rated power level. Laser tests were made in the following manner. A 14 x 3 in. YAGNd rod was pumped in a 10 ft diameter spherical cavity. The rod had antireflection coatings and used external resonators spaced 43 cm apart. The lamps used were NaI-Hg quartz and K-Hg in a single crystal sapphire body. The NaI-Hg lamp resulted in a laser output of 5.65 watts for 920 watts input. The K-Hg lamp produced 9.85 watts for 1000 watts input at a 2 slope efficiency. It is believed that 30 watts output at 4 slope efficiency is attainable for 1000 watts input. Author