Four-Ce:Nd:YAG-rod solar laser with 4.49% conversion efficiency through Fresnel lens

The development of solar laser systems that combine high efficiency and cost-effectiveness is key to the practical implementation of this renewable technology. This paper presents the outcomes of the assessment of a solar laser prototype performed in the focal zone of a Fresnel lens, where it successfully emitted four laser beams at the same time. It featured an aspheric lens, a conical pump cavity, and four Ce:Nd:YAG rods arranged in an end-side pump configuration. A total laser power of 22.46 W was achieved with a 0.9 m collection diameter, corresponding to a 4.49% solar-to-laser power conversion efficiency. This efficiency represents a new benchmark for Fresnel lens systems, reflecting a 16% increase over the previous record. A slope efficiency of 6.76% was also attained, indicating a 7% enhancement. Furthermore, the employment of four rods enabled sustained laser operation for 112 s without reliance on solar tracking assistance. This performance was observed around local solar noon, during which the focal zone underwent a displacement of 0.80° in the azimuthal direction and 0.09° in the altitudinal direction. These outcomes indicate that multirod solar laser systems that involve Fresnel lenses can still be competitive with those employing parabolic mirrors while also being economically advantageous.