High power and uniform distribution of pump-radiation absorption in Nd: YAG solar-laser system with end-side-end pumping method

Abstract

Solar-pumped-laser (SPL) is an appropriate system which can transform the broad-band sunlight into the narrow-band laser directly, with the advantages of simple structure, high efficiency and long lifetime, in an environmentally friendly way, especially in places where the solar-energy is abundant and other energy sources are scarce such as the space. In order to produce the solar-laser light, we must excite the active medium by the solar- light. There are two major techniques for solar-pumping solid-state-lasers: side-pumping and end-side-pumping methods. The solar-laser efficiency advances were achieved by employing end-side-pumping configurations, since they can lead to much higher efficiencies compared to side-pumping configurations. Nevertheless, most of the advances in solar-laser brightness and stability were achieved by side-pumping configurations. The side-pumping method is an effective configuration for power scaling as it allows uniform absorption along the rod axis within the laser medium, hence decreasing the thermal load effects on solar-laser systems. Besides, the free access to both rod ends of side-pumped lasers permits the optimization of more laser resonator parameters, improving largely the laser beam quality and enabling the efficient extraction of solar laser at low modes, when compared to end-pumping configurations. By using the end-side-end pumping configuration, we aimed to benefit from the advantages of the two pumping methods cited above and that's what we effectively achieved and that we report here, a symmetrical and a uniform distribution of radiation along the laser rode axis, as well as a high radiation absorption, which increase the efficiency of the solar-laser system and improve the laser-beam quality