Highly Efficient Four-Rod Pumping Approach for the Most Stable Solar Laser Emission

Abstract

We report a significant numerical improvement in multi-rod laser efficiency, with an enhanced solar tracking error compensation capacity for a heliostat-parabolic system. The solar laser head was composed of a fused silica conical lens and a single conical pump cavity ensuring multiple passes through four 4.55 mm diameter, 15 mm length Nd:YAG rods. 0.76° tracking error width at 10% laser power loss, and total multimode laser power variation of 0.05% at ±0.1° solar tracking error and 0.30% at ±0.2° solar tracking error were numerically calculated, being 1.27, 74.80 and 21.63 times, respectively, more than the experimental record in solar tracking error compensation capacity attained with a dual-rod side-pumping horizontal prototype pumped by the same heliostat-parabolic system. Additionally, the end-side-pumping configuration of the four-rod solar laser-enabled 43.7 W total multimode solar laser power, leading to 24.7 W/m2 collection efficiency and 2.6% solar-to-laser power conversion efficiency, being 1.75 and 1.44 times, respectively, more than that experimentally obtained from the dual-rod side-pumping prototype. The significant improvement in solar tracking error compensation capacity with a highly efficient end-side-pumping configuration is meaningful because it reduces the cost of high-precision trackers for solar laser applications.

Seven-Rod Pumping Concept for Highly Stable Solar Laser Emission

“…Comparison between the results in multimode regime of the present work and the ones from the numerical works by Tibúrcio et al[24], Catela et al[47], Almeida et al[27], and Liang et al[29].…”

“…The TEW 10% in the xand y-axes were 1.41 and 1.86 times higher, and did not display a ∆P asymmetry in both axes as clearly, which is a result of the chosen pumping configuration. In comparison with the most stable four-rod scheme by Catela et al (with D = 4.55 mm, L = 15 mm rods) [47], overall improvements were also attained by the seven-rod approach. The TEW 10% in the xand y-axes were 1.30 and 1.22 times higher, and the ∆P for tracking errors up to ±0.5 • denote a better power stability.…”

“…The proposed seven-rod solar pumping scheme resulted in significant enhancements in comparison with other numerical works that included multiple Nd:YAG rods: the D = 2.15 mm, L = 17 mm in terms of efficiency, and the D = 4.00 mm, L = 13 mm pertaining to tracking error compensation capacity and power stability. Table 2 summarizes the results of the present work and those from four other numerical studies that our research group has conducted: a dual-rod scheme by Tibúrcio et al [24], a four-rod scheme by Catela et al [47], and seven-rod schemes by Almeida et al [27] and Liang et al [29]. Compared to these other proposed seven-rod solar laser concepts, the D = 2.15 mm, L = 17 mm scheme of the present work was more efficient, with 28.5 W/m 2 collection and 3.0% solar-to-laser power conversion efficiencies.…”

Solar laser pumping approach for both simultaneous and stable multibeam operation under tracking error condition

“…49 End-sidepumping configurations lead to higher efficiencies; 18,20,21,34 however, focusing the concentrated solar radiation onto the end face of a single laser rod is not favorable for enhancing the solar tracking error compensation capacity. 49 Therefore, in the same year, Catela et al 50 studied a fourrod end-side-pumping solar laser concept. Numerical analysis proved the high-efficiency characteristic of end-side-pumping configurations, while attaining 0.76 deg TEW 10% .…”

Stable Emissions from a Four-Rod Nd:YAG Solar Laser with ±0.5° Tracking Error Compensation Capacity

“…End-side-pumping schemes lead to higher efficiencies; however, focusing the concentrated solar radiation onto the end face of a single laser rod requires a highly accurate STS [15]. Therefore, multi-rod end-side-pumping solar laser designs were numerically studied, demonstrating the higher efficiency of end-side-pumping configurations as compared to that of side-pumping, while attaining high solar tracking error compensation capacity [20,21]. Furthermore, multibeam laser systems hold tremendous potential for significantly reducing processing time in industry [22].…”