The output of Nd∶YAG single pass laser amplifiers is studied analytically and experimentally. Methods of analysis for single pass Nd∶YAG laser amplifier are presented. A flashlamp-pumped Q switched Nd∶YAG oscillator/amplifier laser system has been developed with the average output power of 121.5 W. The output of Nd: YAG single pass laser amplifiers is studied and experimentally. Methods of analysis for single pass Nd: YAG laser amplifiers are presented. A flashlamp-pumped Q switched Nd: YAG oscillator / amplifier laser system has been developed with the average output power of 121.5 W.