Influence of thermal population of lower laser levels on the performance of end-side-pumped Ce:Nd:YAG solar laser

Abstract

.We report the results of a theoretical study of the combined end-side pumped solar lasers to solve the problem associated with a recent experimental finding where the unexpected underperformance of the Ce doped Nd:YAG lasers in comparison to pure Nd:YAG lasers was observed. For this, we have developed a theoretical model based on space-dependent rate equations, which considers the effect of the thermal population of the laser levels on the laser output. It is shown that the main reason for the lower laser performance of recently experimentally realized Ce:Nd:YAG solar laser in the end-pumped regime and the fracture of the Ce:Nd:YAG rod at the process is the excessively high thermal load on the end of the laser rod. As a result of our study, we propose easily-feasible solutions based on optimal pumping and cooling configurations. The results of this study also demonstrate that under the necessary conditions, using Ce:Nd:YAG as an alternative to Nd:YAG in the combined end-side pumping configuration could increase the laser output by more than 1.5 times.

Solar-pumped composite YAG/Ce:Nd:YAG/YAG laser with reduced thermal effects

“…The tendency for smaller crystals to have higher solar-to-laser power conversion efficiency leads us to conclude that thermal effects may be more significant in solar-pumped lasers than currently believed. 5 This statement is further supported by the fact that an efficiency of 3.85% was obtained in a study with a laser rod diameter of 6 mm and better cooling conditions (by using a quartz tube), as reported in Ref. 12, compared to our case with a Fig.…”

“…If thermal loads become significant, it will negatively affect the laser output. 5 As can be seen from Fig. 9, a composite laser rod, when optimizing the noted parameters, allows one to obtain significantly improved results comparable to those obtained using conventional noncomposite crystals of similar sizes while the thermal load on the front part remains unchanged.…”

“…The solar laser output is calculated using a formulation described in our previous studies, 5 , 9 based on the data presented in Table 1: ϕ=τc∭volumeRp(1+f)−fNt/τ(1+f)+V/(ϕcσeτ|u|2)dV.…”

“…2 Later, the Ce:Nd:YAG laser crystal was experimentally tested for the first time in an end-side-pumped solar laser configuration, but it reported inferior performance. 3 This prompted further studies, where authors investigated the sensitization properties of Ce:Nd:YAG 4 and thoroughly examined thermal effects in another study, 5 concluding that Ce:Nd:YAG is expected to perform better in comparison with Nd:YAG lasers. Finally, in a milestone experimental work, a significant advancement in the Ce:Nd:YAG solar laser performance using a side-pumping configuration was reported, 6 as expected.…”

“…In addition to the experiment in this work, to interpret and analyze the experimental results, we carried out simulation calculations using our thermal model described in Ref. 5.…”