GAIN SATURATION IN SINGLE-PASS AND DOUBLE-PASS OPTICALLY PUMPED LASER-AMPLIFIERS

The operation of an optically pumped laser amplifier has been studied for two different geometries: the single pass and the double pass configurations. The influence of superflourescent emission, self-absorption of the laser emission and pump beam depletion have been included. Our results indicate that for a longitudinally pumped amplifier configuration, a multipass geometry is a disadvantage since it results in higher loss through enhanced superfluorescent emission and self absorption. Also, more passes do not result in increased pin length because of a substantial depletion in the pump beam energy. Thus, only for low laser input signals is the stage pin for the double pass amplifier higher than that for the single pass amplifier.