Theoretical Study About Solar Pumped Lasers

Solar pumped lasers have obvious advantages for applications in the fields of space, energy, communication, material processing and so on. But now the output power and the energy conversion efficiency of solar pumped laser is still relatively low. The laser material is a key factor to improve the output power and energy conversion efficiency. In order to select suitable solar pumped laser materials, a theoretical model is established based on the four-level rate equation, and it takes the solar spectrum into account. By the model, the pump intensity thresholds of Nd³⁺:YAG, Nd³⁺:glass, Nd:Cr:GSGG (Nd³⁺:Cr³⁺:Gd₃Sc₂Ga₃O₁₂), Cr³⁺:BeAl₂O₄ and Cr³⁺:Nd³⁺:YAG ceramic for the different pump schemes are analyzed. The results show that the pump intensity threshold of Nd³⁺:YAG is 448 sun constant when it is side pumped by a single beam and is 224 sun constant when it is side pumped inside a ellipsoidal cavity, respectively. It implies that Nd³⁺:YAG is the better suitable laser material for the solar pumped. Due to the special structure of the ellipsoidal cavity, the pump intensity threshold is relatively low when it is side pumped inside a ellipsoidal cavity. Also analyzed the relationship between the pump intensity threshold and the diameter of the material. The model could be applied to other materials.