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Kilowatt-class visible solar-pumped alexandrite lasers for application of Mg renewable recovery from MgO
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Quasi-Gaussian Multibeam Solar Laser Station for a Megawatt Solar Furnace
Publication . Costa, Hugo; Almeida, Joana; Liang, Dawei; Tibúrcio, Bruno D.; Garcia, Dário; Catela, Miguel; Vistas, Cláudia Alexandra da Rocha; DF – Departamento de Física; CeFITec – Centro de Física e Investigação Tecnológica
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/m2 collection efficiency and a 2.0% solar-to-laser power conversion efficiency.
Efficient Production of Doughnut-Shaped Ce:Nd:YAG Solar Laser Beam
Publication . Garcia, Dário; Liang, Dawei; Almeida, Joana; Catela, Miguel; Costa, Hugo; Tibúrcio, Bruno D.; Guillot, Emmanuel; Vistas, Cláudia R.; DF – Departamento de Física; CeFITec – Centro de Física e Investigação Tecnológica; Molecular Diversity Preservation International (MDPI)
Laser beams with a doughnut-shaped profile have garnered much attention for their contribution to trapping nanoparticles and improving the scanning speed during laser-based 3D metal printing. For this reason, the production of a doughnut-shaped solar laser beam by end-side pumping a Ce:Nd:YAG rod with a small reflective parabolic collector was investigated. The resultant beam profile shape depended on the absorbed solar power, displaying a TEM00-mode profile at elevated input power. This phenomenon was primarily attributed to the role of distributing energy around the central region of the crystal. In contrast, at lower input power, a doughnut-shaped beam emerged, characterized by minimal energy distribution at the center. Through experiments conducted with a collection area of 0.226 m2 and a nominal solar irradiance from 970 W/m2 to 1000 W/m2, it was demonstrated that sufficient energy was available to generate a doughnut-shaped beam with a solar laser collection efficiency of 5.96 W/m2, surpassing previous measurements by 1.32 times. Further research with a larger collection area of 0.332 m2 and a diverse solar irradiance range of 650 W/m2 to 800 W/m2 revealed that the presence of a thin layer of cloud caused a transition from a doughnut-shaped to a TEM10-mode and, eventually, a TEM00-mode as the absorbed input solar power increased. Notably, under heavier cloud cover, the laser beam exhibited deformation at low input power instead of maintaining a doughnut-shaped profile. This research significantly enhances our comprehension of doughnut-shaped solar laser beams and their reliance on solar energy. By harnessing the plentiful and readily accessible energy from the Sun, the incorporation of solar energy into the realm of solar-pumped lasers holds immense promise for promoting sustainability. This transformative utilization can progressively diminish the industry’s carbon footprint, yielding long-term environmental benefits.
Four-Ce:Nd:YAG-rod solar laser with 4.49% conversion efficiency through Fresnel lens
Publication . Costa, Hugo; Liang, Dawei; Almeida, Joana; Tibúrcio, Bruno D.; Vistas, Cláudia R.; DF – Departamento de Física; CeFITec – Centro de Física e Investigação Tecnológica; Nature Publishing Group
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.
Fresnel Lens Solar Pumping for Uniform and Stable Emission of Six Sustainable Laser Beams under Non-Continuous Solar Tracking
Publication . Vistas, Cláudia R.; Liang, Dawei; Catela, Miguel; Costa, Hugo; Garcia, Dário; Tibúrcio, Bruno D.; Almeida, Joana; CeFITec – Centro de Física e Investigação Tecnológica; DF – Departamento de Física; Molecular Diversity Preservation International (MDPI)
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.
Seven-Rod Pumping Concept for Highly Stable Solar Laser Emission
Publication . Costa, Hugo; Liang, Dawei; Almeida, Joana; Catela, Miguel; Garcia, Dário; Tibúrcio, Bruno D.; Vistas, Cláudia R.; DF – Departamento de Física; CeFITec – Centro de Física e Investigação Tecnológica; MDPI - Multidisciplinary Digital Publishing Institute
A seven-rod solar laser head was conceptualized and numerically studied to improve the tracking error compensation capacity and power stability in end-side-pumping schemes. It was composed of a first-stage heliostat–parabolic mirror system, a second-stage fused silica aspheric lens and a third-stage conical pumping cavity, within which seven Nd:YAG rods were mounted. Highly stable solar laser emission, with a power loss inferior to 5% for tracking errors up to ±0.4°, could potentially be enabled with seven 4 mm diameter, 13 mm length rods. The tracking error width at 10% laser power loss was about 1.0°, which is 1.65 times higher than the experimental record, attained by a dual-rod side-pumping prototype. Furthermore, a total multimode laser power of about 41.2 W could also be achieved, corresponding to 23.3 W/m2 collection and 2.5% solar-to-laser power conversion efficiencies, which are 1.65 and 1.36 times higher than those obtained with the dual-rod side-pumping prototype. They are also 1.27 and 1.12 times higher than the multirod experimental records in multimode regime for the same rod material.
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SFRH/BPD/125116/2016