DIRECT MEASUREMENTS OF THE TERMINAL LASER LEVEL LIFETIME IN NEODYMIUM-DOPED CRYSTALS AND GLASSES

We have measured the terminal level lifetime (tau 11/2) for the 1-mu m neodymium transition in several laser media, using a novel pump (2.41 -mu m) and probe (1.06-mu m) technique. This method allows us to popul ate the (4)I13/2 level directly and subsequently to monitor the termin al level (4)I11/2 population as a function of time by observing the ch ange in integrated fluoresence of the 0.88-mu m emission for each time delay between the pump and the probe pulses. We developed a computer model to analyze the data and determined the upper and lower limits fo r the tau 11/2 lifetime. The results for some of the materials investi gated are 115-225 ps for Nd:Y3Al5O12, 250-450 ps for Nd:LG-750 (phosph ate glass), 535-740 ps for Nd:LG-660 (silicate glass), 896-1900 ps for Nd:YAlO3, and 10.5-20 ns for Nd:YLiF4. In addition, we found the life times to be independent of the neodymium doping concentration for the phosphate and silicate glass samples investigated. (C) 1995 Optical So ciety of America