DEPENDENCE OF LASER SINGLE-PULSE CHARACTERISTICS ON ACTIVE ROD LENGTH,
FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OHIO
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The dependence of population inversion on rod length in the case of ruby and neodymium glass laser rods was investigated. The required pumping rates at a given rod length increase with gain in a nonlinear manner. The population inversion drops with increasing rod length. The formulas describing the above relationship make it possible to estimate the total energy stored in a rod of certain length at any pumping input. The energy storage curves as a function of rod length reach their maximum and level off at rod lengths of 10 to 20 cm for both ruby and glass. The radiation power as a function of rod length, however, shows a maximum around the 10-cm rod length and then diminishes with longer rods because of the Fresnel reflection from the ends. The most efficient laser action, according to the calculations, can be achieved with rapid about 1 to 10 nsec in 3- and 4-level lasers Q-switching, provided the dependence of emitted power on the coefficient of useful losses is investigated and the position of its maximum is determined.
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