Amplified spontaneous emission (ASE) effect on gain and stored energy

In this research, amplified spontaneous emission (ASE) is studied along a rod amplifier length where intensities travel in two opposite longitudinal axis directions. The effect of ASE intensity on amplifier stored energy was discussed. An expression was obtained for stored energy in an amplifier in which a nonuniform gain distribution shaped due to ASE saturation effect. Time evolution of population inversion in a pulsed amplifier at the presence of ASE effect was also obtained, using the new relation of stored energy. Numerical calculations were used to verify accuracy and validity of the obtained relations. The numerical calculations included solving rate equation of population inversion of amplifier and simultaneous solving of two intensity equations for two beams traveling in opposite directions along the amplifier length.