885nm Directly Pumped Nd: YAG Laser

In diode pumped Nd:YAG lasers, the quantum defect is the most important parameter determining the thermal load of the laser crystal. This can be reduced dramatically by direct pumping into the upper laser level. However, for the direct pumping, the absorption cross section of the Nd3+ ion is small in order to absorb adequate pumping power, high Nd3+ concentration is necessary. This requirement may bring some problems, such as concentration-dependent fluorescence quenching, variations of pumping and laser modes, etc, so Nd3+ concentration have a potent effect on direct-pumping. Therefore, the paper will make a deep study, the following is the main work and results:1.The principle and the effect on beam quality of the thermal load are analyzed. Introduce the reason of reduce the thermal load by direct pumping.2.Through the theoretical derivation and numerical calculation, we get the value of the slope efficiencies for incident and absorbed pumping powers as well as the incident and absorbed pumping thresholds of Nd3+:YAG laser under indirect and direct pumping with different Nd3+ concentration. Afterwards, the discrepancy between them is analyzed.3.Carry out an experiment with indirect(809nm) and direct(885nm) pumping Nd3+:YAG laser, the results of the experiment are practical unanimity with the theoretical derivation, therefore, in the case of the slope efficiency for the absorbed pumping power and the absorbed pumping threshold, the direct pumping is always better than the indirect pumping.