High-efficiency solar laser pumping by a modified ring-array concentrator

To considerably improve solar laser efficiency, a 5.5 mm diameter 20 mm length Nd:YAG single-crystal rod can be efficiently pumped by highly concentrated solar radiation through a modified ring-array concentrator. Composed of several coaxial parabolic reflective rings and a small diameter Fresnel lens, the 1.5 m diameter modified ring-array concentrator can focus tightly incoming solar radiation into a 5.0 mm full width at half maximum focal spot. An innovative aspherical fused silica concentrator allows further pump light concentration into the Nd:YAG rod at the focal zone. A simple water cooling scheme within the aspherical concentrator constitutes another highlight of this scheme. Strong dependency of solar laser power on the rim angle of the ring-array concentrator was found through ZEMAX™ and LASCAD© analyses. 67.8 W continuous-wave 1064 nm solar laser power at 38.4 W/m2 collection efficiency was numerically calculated, being 1.22 times more than the previous record. Besides, 1.29, 1.03 and 1.85 times improvements in conversion, slope efficiencies and brightness figure of merit, respectively, were numerically achieved. The tracking error influence on solar laser output power was numerically calculated.