Optical pulse propagation in a heavily saturated laser amplifier: laser parameter analysis

An optical pulse propagating through a partially homogeneously broadened laser amplifier is analyzed theoretically and experimentally in the heavily saturated region as well as in the linear and slightly saturated regions. In the heavily saturated region pulse shortening takes place, whereas pulse lengthening is observed in the linear or slightly saturated region. Emphasis is especially placed on a laser parameter analysis by using the formulas for the pulse-peak irradiance, the pulse duration, and the pulse-delay time. A new method to determine the saturation irradiance I/sub s/ of the laser medium is proposed based on the condition for maximizing the pulse-delay time. By demonstrating the above method and the methods in the linear region to the 3.5-..mu..m line of a He-Xe laser, we have obtained the following laser parameters: The saturation irradiance I/sub s/ is 6.34 ..mu..W/mm/sup 2/, the gain parameter G is 0.063 cm/sup -1/, the Lorentzian linewidth ..delta nu../sub L/ is 11.7 MHz, and the Doppler linewidth ..delta nu../sub D/ is 104 MHz.