A Compact Solar Laser Side-Pumping Scheme Using Four Off-Axis Parabolic Mirrors

Laser side-pumping approach is an extremely attractive configuration for many laser applications. Through this approach, the laser beam can be generated in the lowest possible spatial modes, with the highest beam brightness and quality. In this study, a significant improvement in the solar laser output power and collection efficiency of a side-pumped Nd:YAG laser rod, with a length of 84 mm and a diameter of 7.5 mm, is numerically achieved using four off-axis primary parabolic mirrors with a total collection area of 10 m2. Four fused-silica aspheric-lens secondary concentrators are used to efficiently couple the concentrated solar power from the four focal zones of the off-axis parabolic mirrors into a single laser rod enclosed within four 2V-shaped pump cavities. The optimum solar-laser design parameters are determined using the ZEMAX© nonsequential ray-tracing and LASCAD© laser-cavity analysis software. A power of 346.8 W continuous-wave 1064 nm solar laser is determined numerically in the multimode operation. This corresponds to a solar laser collection efficiency and solar-to-laser power conversion efficiency of 34.7 W/m2 and 3.84%, respectively, which demonstrate an improvement of 2.04 and 1.58 times, respectively, over the existing experimental record for side-pumped Nd:YAG solar lasers.