Energy output degradation of Czochralski ruby lasers

Extensive comparisons of Czochralski and Verneull ruby lasers have been made; such tests have become important due to the recent lack of availability of Verneuil ruby. The principal point of this paper is that the energy output of a long pulse Czochralski ruby laser gradually drops until after several hundred firings it has decreased to about 20% of its initial value. We have observed this in all Czochralski rods tested but have seen only slight evidence of this in Verneuil ruby. Two batches of Czochralski ruby were tested, one grown in 1964 and the other early in 1966. No simple explanation (such as a change in threshold or the development of damage in the rod) has been found yet which can explain the decreases seen for the two batches; within each batch, however, the symptoms are approximately uniform from rod-to-rod. All Czochralski crystals, however, do develop an orange coloration. Some exhibit a decrease in R1line absorption, and an increase in absorption at 4800A as seen by Hoskins and Soffer and Schultz; they attribute the 4800A absorption increase to defects created in the crystal. Our data interpretation, to date, indicates that these types of changes can only barely explain the decrease in energy observed. Tests will be continued to determine what effect pyrex has on filtering the pump light.