Design of TEM00 mode side-pumped Nd:YAG solar laser

An alternative solar laser pumping approach is here proposed to improve substantially TEM00 mode solar laser power. The solar radiation is both collected and concentrated by four Fresnel lenses, and redirected towards a laser head by four plane folding mirrors. A secondary concentrator with four semi-cylindrical fused silica lenses is designed to compress the highly concentrated solar radiation to a Nd:YAG single-crystal rod. Optimum pumping conditions and laser resonator parameters are found through ZEMAX© and LASCAD© numerical analysis. The proposed design offers a uniform absorbed pump distribution along the laser rod which has a minimum in its central region, reducing considerably thermal lensing effects. High order mode laser power of 83 W is numerically attained with a short symmetric laser resonant cavity, leading to high collection efficiency of 20.8 W/m2 for side-pumped Nd:YAG solar laser. Large spatial overlap between the pumped volume and the fundamental mode volume is found for an asymmetric laser resonator with concave end mirrors of large radius of curvature. 47.4 W TEM00 laser output power is numerically achieved, leading to a solar laser beam brightness figure of merit of 32 W. This value is 16.8 times more than the previous record for solar-pumped laser.