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Projeto de investigação
Converting solar laser power into UV, VIS and IR laser power
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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.
Uniform and Non-Uniform Pumping Effect on Ce:Nd:YAG Side-Pumped Solar Laser Output Performance
Publication . Vistas, Cláudia R.; Liang, Dawei; Garcia, Dário; Catela, Miguel; Tibúrcio, Bruno D.; Costa, Hugo; Guillot, Emmanuel; Almeida, Joana; CeFITec – Centro de Física e Investigação Tecnológica; DF – Departamento de Física; MDPI - Multidisciplinary Digital Publishing Institute
The Ce:Nd:YAG is a recent active medium in solar-pumped lasers with great potential. This study focuses on the influence of two secondary concentrators: a fused silica aspherical lens and a rectangular fused silica light guide; and consequent pump light distribution on the output performance of a Ce:Nd:YAG side-pumped solar laser. The solar laser head with the aspherical lens concentrated the incident pump light on the central region of the rod, producing the highest continuous-wave 1064 nm solar laser power of 19.6 W from the Ce:Nd:YAG medium. However, the non-uniformity of the absorbed pump profile produced by the aspherical lens led to the rod fracture because of the high thermal load, limiting the maximum laser power. Nevertheless, the solar laser head with the light guide uniformly spread the pump light along the laser rod, minimizing the thermal load issues and producing a maximum laser power of 17.4 W. Despite the slight decrease in laser power, the use of the light guide avoided the laser rod fracture, demonstrating its potential to scale to higher laser power. Therefore, the pumping distribution on the rod may play a fundamental role for Ce:Nd:YAG solar laser systems design.
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.
Stable Emissions from a Four-Rod Nd:YAG Solar Laser with ±0.5° Tracking Error Compensation Capacity
Publication . Catela, Miguel; Liang, Dawei; Almeida, Joana; Costa, Hugo; Garcia, Dário; Tibúrcio, Bruno D.; Guillot, Emmanuel; Vistas, Cláudia R.; CeFITec – Centro de Física e Investigação Tecnológica; MDPI - Multidisciplinary Digital Publishing Institute
Conventional solar-pumped lasers rely on expensive and highly accurate solar tracking systems, which present a significant economic barrier to both solar laser research and practical applications. To address this challenge, an end-side-pumped four-rod solar laser head was designed and built for testing at PROMES-CNRS. Solar radiation was collected and concentrated using a heliostat–parabolic mirror system. A fused silica aspheric lens further concentrated the solar rays into a flux homogenizer within which four Nd:YAG rods were symmetrically positioned around a reflective cone and cooled by water. Four partially reflective mirrors were precisely aligned to extract continuous-wave 1064 nm solar laser power from each laser rod. The prototype demonstrated stable multibeam solar laser operation with the solar tracking system turned on. Even when the tracking system was turned off, the total output power extracted from the solar-pumped laser remained stable for 1 min, representing, to the best of our knowledge, the first successful demonstration of a stable multibeam solar laser operation without solar tracking. For typical solar tracking errors up to ±0.5°, the loss in the total solar laser power produced was only about 1%, representing an 8.0-fold improvement over the previous solar laser experiments under tracking error conditions.
High Brightness Ce:Nd:YAG Solar Laser Pumping Approach with 22.9 W/m2 TEM00-Mode Collection Efficiency
Publication . Vistas, Cláudia R.; Liang, Dawei; Costa, Hugo; Catela, Miguel; Garcia, Dário; Tibúrcio, Bruno D.; Almeida, Joana; CeFITec – Centro de Física e Investigação Tecnológica; DF – Departamento de Física; MDPI - Multidisciplinary Digital Publishing Institute
A compact side-pumped solar laser design using a Ce:Nd:YAG laser medium is here proposed to improve the TEM00-mode solar laser output performance, more specifically the beam brightness. The solar laser performance of the Ce:Nd:YAG laser head was numerically studied by both ZEMAX® v13 and LASCADTM v1 software. Maximum multimode laser power of 99.5 W was computed for the 4.1 mm diameter, 34 mm length grooved rod, corresponding to a collection efficiency of 33.2 W/m2. To extract TEM00-mode solar laser, symmetric and asymmetric optical resonators were investigated. For the 4.1 mm diameter, 34 mm length grooved rod, maximum TEM00-mode solar laser collection efficiency of 22.9 W/m2 and brightness figure of merit of 62.4 W were computed using the symmetric optical resonator. While, for the asymmetric optical resonator, the maximum fundamental mode solar laser collection efficiency of 16.1 W/m2 and brightness figure of merit of 37.3 W were numerically achieved. The asymmetric resonator offered a TEM00-mode laser power lower than the one obtained using the symmetric resonator; however, a collimated laser beam was extracted from the asymmetric resonator, unlike the divergent TEM00-mode laser beam provided by the symmetric resonator. Nevertheless, using both optical resonators, the TEM00-mode Ce:Nd:YAG solar laser power and beam brightness figure of merit were significantly higher than the numerical values obtained by the previous Nd:YAG solar laser considering the same primary concentrator.
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Fundação para a Ciência e a Tecnologia
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SFRH/BD/145322/2019