Mathematical model of generation and amplification of radiation in multistage laser

We propose a mathematical model of a multistage laser based on three- and four levels of active media in the plane wave approximation. The model can be used to analyze the radiation generating process in the laser source in the presence of interstage links allowing for actual quality of the optical path elements. The paper gives calculation of pulse parameters of YAG: Nd and YSGG: Cr: Nd laser generator depending on the pump power. Findings of the research will be useful for solving problems of laser emitter complex optimization and determining the requirements for interstage cross coupling nodes.