LUMINESCENCE IN POTENTIAL FLUORIDE GLASS LASERS

Abstract
Fluoride glasses of the zirconium barium lanthanide type (invented Rennes, 1975) and lead gallium zinc (or manganese) type (invented Le Mans, 1979) show luminescence of lanthanide J-Levels situated at least 2000 cm^-1 above the closest lower level (this limit is a few times larger in most other materials). Not only is the non-radiative de-excitation as weak as incrystalline LaF₃ (studied by Weber) but energy transfer between neodymium and ytterbium (III), or from manganese (II), and to some extent from chromium (III), to luminescent J-levels of neodymium (III), erbium(III) and thulium (III) is highly efficient even at low concentrations. One advantage for laser applications is that the lowest quartet state of manganese (II) has a life-time 10 to 15 milliseconds (like in many phosphate glasses and crystalline compounds) allowing energy transfer, extending by huge factors the average life-time of the emitting J-levels. Though the terawatt lasers (Livermore, California, 1978) inducing deuterium-tritium fusion are silicate glass containing neodymium (III), fluoride glasses should be preferable for many purposes. The evaluation of laser parameters from small-scale experimentation is feasible.