Measurements of transient gain and loss in solid state VUV laser materials

There is considerable interest in the possibility of generating continuously tunable VUV laser radiation based upon d-f transitions in rare-earth doped fluorides such as LiLuF/sub 4/:Ce/sup 3+/. The observation of VUV laser oscillation in many of these systems is hampered by the large absorption losses caused by even low levels of impurities, and so in order to ascertain the prospects for achieving laser oscillation it is useful to determine the net optical gain in the presence of such loss. We have developed a diagnostic approach based upon the measurement of the intensity of the amplified spontaneous emission as a function of the length of the crystal which is pumped.