Fresnel Lens Solar Pumping for Uniform and Stable Emission of Six Sustainable Laser Beams under Non-Continuous Solar Tracking

Abstract

A multirod solar laser approach is here proposed to attain uniform and stable multibeam emission under non-continuous solar tracking. A Fresnel lens was used as the primary concentrator. The laser head was composed of a second-stage aspherical lens with a light-guide homogenizer and a third-stage conical pump cavity with six Nd:YAG rods. The solar laser system was optimized through numerical analysis in both Zemax® and LASCAD™ software to obtain six 1064 nm laser beams of similar multimode power. To investigate the effect of the homogenizer on the laser performance, the laser head was compared with a similar one that only used the aspherical lens in the second stage. The approach with the light guide attained a slightly lower efficiency than the one without the light guide; however, the tracking error width at 10% laser power loss was higher and, most importantly, only a 2.17% coefficient of variation of the laser power emitted by the six rods at the tracking error angle of ±0.5° was obtained. This is 4.2 times better than the 52.31% obtained with the laser head without the homogenizer and 76 times better than that of the previous numerical work. The light guide is thus essential to ensure uniform and stable solar laser power extraction from all rods even under non-continuous solar tracking, making this prototype the ideal for multibeam laser applications where uniformity and stability of the laser power are indispensable. This renewable multibeam solar laser may replace the classical lamp- and diode-pumped lasers, therefore ensuring a sustainable laser power production pattern for both space and terrestrial applications.