The Physics Society of Iran Iranian Journal of Physics Research 1682-6957 11 2 2019 11 26 Pulse propagation in a two-pass optical amplifier with arbitrary laser beams overlap Pulse propagation in a two-pass optical amplifier with arbitrary laser beams overlap 117 128 916 FA AH Farahbod F Tahsildaran Fard Journal Article 2019 11 26 An analytical model for two-pass optical amplifier with arbitrary beams overlap has been developed which generalized the classical theory of Frantz-Nodvik for single pass amplifier. The effect of counterpropagating beams on gain and output energy fluence included in the model. Moreover, the appropriate limiting relations for two special cases of weak input signal and saturation state of the amplifier gain have been derived. The results indicate that for complete beams overlap, the gain and output energy have the least values. The model predictions are consistent with experimental observations and exact analytical model for two-pass amplifier when beam propagation paths are coincided. An analytical model for two-pass optical amplifier with arbitrary beams overlap has been developed which generalized the classical theory of Frantz-Nodvik for single pass amplifier. The effect of counterpropagating beams on gain and output energy fluence included in the model. Moreover, the appropriate limiting relations for two special cases of weak input signal and saturation state of the amplifier gain have been derived. The results indicate that for complete beams overlap, the gain and output energy have the least values. The model predictions are consistent with experimental observations and exact analytical model for two-pass amplifier when beam propagation paths are coincided. https://ijpr.iut.ac.ir/article_916_23ce1851341ec1fa9e0c259de10bf87c.pdf