Quasi-Gaussian Multibeam Solar Laser Station for a Megawatt Solar Furnace

Abstract

An alternative multirod solar side-pumping concept for the production of multiple quasi-Gaussian beams is proposed. This scheme was based on the One-Megawatt solar furnace in Odeillo, France, which collected and concentrated the solar light into a multilayered pyramidal pumping cavity placed at the focal zone. Each layer was comprised of a square array of four laser heads, each composed of a biconic surface that reflected the solar rays towards a Nd:YAG rod fixed inside a fused silica flow tube. A pyramidal reflector was placed inside the pumping cavity to close it and maximize the harness of solar energy. Compared to the previous multibeam solar laser station design for the same solar furnace, considerable alleviation of thermal lensing effects was achieved with the present approach, allowing the improvement of the laser beam quality factors and, consequently, the possibility of a 32-laser-beam generation, each with a quasi-Gaussian profile. For this case, 9.44 kW total laser power was calculated. Additionally, 20.01 kW total multimode laser power was numerically determined, which corresponds to a 10.93 W/m 2 collection efficiency and a 2.0% solar-to-laser power conversion efficiency.

Zigzag Multirod Laser Beam Merging Approach for Brighter TEM00-Mode Solar Laser Emission from a Megawatt Solar Furnace

“…It was composed of a hexagonal shaped solar flux homogenizer with a fused silica window at its output end face, and 1657 core-doped Nd:YAG rods surrounded by a hexagonal reflector. The presence of the homogenizer facilitated the distribution of nearly the same amount of solar power to pump each rod and the substantial mitigation of the thermal lensing effects on each one, to the point that they were much less pronounced than in [38]. This facilitated the use of thin rods and long resonator cavities that are necessary to efficiently extract TEM 00 -mode solar laser beams.…”

“…In this end-side-pumping scheme, the thermal lensing effects were much less noticeable than in the previous 32-rod side-pumping concept with 6-mm diameter rods for the same solar furnace [38]. This made the use of thinner rods possible, which were pivotal in maximizing the TEM00-mode laser power extraction with much longer resonant cavities.…”

“…It has proven its effectiveness in applications such as welding, brazing, surface texturing [28], microstructuring [29], laser ablation, drilling, and cutting [30,31], achieving more positive outcomes compared to that with the conventional single laser beam. In similar fashion, researchers have been proposing concepts based on the distribution of concentrated radiation among multiple rods [32][33][34][35][36][37][38][39] to abate the thermal stress effects. Through numerical work, multirod laser stations have shown great potential to be used in megawatt solar furnaces (MWSF) [32,36,38].…”

“…In similar fashion, researchers have been proposing concepts based on the distribution of concentrated radiation among multiple rods [32][33][34][35][36][37][38][39] to abate the thermal stress effects. Through numerical work, multirod laser stations have shown great potential to be used in megawatt solar furnaces (MWSF) [32,36,38]. For the MWSF of Procédés, Matériaux et Energie Solaire-Centre National de la Recherche Scientifique (PROMES-CNRS), total multimode solar laser power of 22.84 kW was numerically attained from a side-pumping laser system with a solar flux homogenizer and 12 Nd:YAG rods of 10 mm diameter and 516 mm length, resulting in 12.48 W/m 2 collection and 2.28% solar-to-laser power conversion efficiencies [36].…”

“…This concept, however, displayed strong thermal lensing in each rod, impairing the laser beam quality. In consideration of this, a 32-rod side-pumping scheme was proposed for that same facility [38]. With rods of 6 mm diameter and eight different lengths, it showed a considerable alleviation of the thermal lensing effects and improvement of the laser beam quality factors, possibly enabling the generation of 9.44 kW total laser power from 32 laser beams with quasi-Gaussian profiles.…”