Highly efficient end-side-pumped Nd:YAG solar laser by a heliostat–parabolic mirror system

We report a large improvement in the collection and slope efficiency of an Nd:YAG solar laser pumped by a heliostat–parabolic mirror system. A conical fused silica lens was used to further concentrate the solar radiation from the focal zone of a 2 m diameter primary concentrator to a Nd:YAG single-crystal rod within a conical pump cavity, which enabled multipass pumping to the active medium. A 56 W cw laser power was measured, corresponding to $21.1\mathrm{W}/{\mathrm{m}}^2$ record-high solar laser collection efficiency with the heliostat–parabolic mirror system. 4.9% slope efficiency was calculated, corresponding to 175% enhancement over our previous result.