Numerical simulating of diode-side-pumped Nd ~(3+): YAG rod la-ser performance

摘要

Previously we carried out experiments with diode-side-pumped Nd~( 3+):YAG rod lasers with varies configurations of pumping module. All the important output laser characteristics -free-running (FR) and Q-switched (QS) pulse energy, slope and light-to light efficiency, beam divergence were investigated as a functions of diodes parameters, pumping module and a rod geometry, neodymium concentration and resonator configuration. In result of this study we determined an optimal pumping module and resonator parameters witch provide the most effective laser operation. To achieve sufficiently high effective transmission from laser diodes (LD) into a rod we used multy-sectioned pumping modules with four- and eightfold symmetry in which LD's were mounted close-coupled to an active element (AE) (Fig.1 a, b). Really we realized laser free-running operation with slope efficiency of 55% in case of eightfold module geometry and of 45% in case of fourfold one. These results were achieved thanks to high exciting emission density obtained near the central axes of a rod. The same time as a visualization of spontaneous emission showed spatial distribution of inversed population was very nonuniform and it should be a reason of low quality of output beam. Further experimental study of Nd~(3+):YAG 5-mm-rod laser output in far field showed the possibility to decrease sufficiently a beam divergence of about 2-3 times within negligible losing of slope efficiency despite on gain nonuniformity. This result evidenced that output laser emission spatial distribution in far field depended mainly on the resonator configuration and the slope and the overall efficiencies mainly depended on overlap of the beam and the gain distributions.