MODELLING OF MODE OVERLAP IN LONGITUDINALLY PUMPED SOLID STATE LASERS

Abstract
In our paper we investigated the influence of the mode overlap on the efficiency of longitudinally pumped solid state lasers. In a theoretical part we enhanced an existing model for four level lasers from idealized cylindrical modes to arbitrary pump and laser modes in a random relative position. Theoretical predictions were confirmed experimentally with an end-pumped Nd:YAG rod operated at 1064 nm. To investigate the effect of misalignment on the efficiency we used a Ti-Sapphire pump laser which could be displaced relative to the laser beam. In a second experiment a diode laser equipped with coupling optics served as the pump source for the same resonator. This resulted in a 20 % decrease in slope efficiency compared to the Ti-Sapphire pumped system due to the limited mode overlap produced by the diode coupling optics.