Pulse length and terminal-level lifetime dependence of energy extraction for neodymium-doped phosphate amplifier glass

On the basis of detailed numerical calculations, we have formulated an empirical expression for the saturation fluence in neodymium-doped phosphate amplifier glass that explicitly depends upon the ratio of the pulse width to the terminal-level lifetime. The empirical expression, when substituted within the Frantz-Nodvik solution for energy extraction, can be used to determine the impact of the lower level lifetime on the energy extracted from Nd:phosphate glass amplifiers. We used our empirical solution to model experimental gain-saturation data and determine the terminal-level lifetime. We compared this value with two independent experiments and found that all three experiments yielded similar results. The terminal-level lifetime of LG-750 at room temperature is found to be 253 ps /spl plusmn/50 ps.