A three-dimensional ring-array concentrator solar furnace

PD/BD/142827/2018. PD/BD/128267/2016. SFRH/BPD/125116/2016. CEECIND/03081/2017. UID/FIS/00068/2019. Sem PDF conforme despacho.A single ring-array concentrator solar furnace unit was firstly modeled analytically, and then optimized numerically by ZEMAX® and ANSYS® software, reaching a temperature of 3778 K, nearly equivalent to that of a medium size solar furnace with 3.14 m2 collection area. A novel three-dimensional ring array concentrator solar furnace was subsequently proposed and analyzed. It consisted of five single ring array concentrators, forming a compact box-shaped solar furnace with an opening at the rear side for an easy access to a common focal spot in the center. Based on the edge-ray principle of non-imaging optics, 30,960 solar concentration ratio was analytically calculated for this solar furnace, leading to significantly enhanced thermal and optical efficiencies. The temperature performance of the three-dimensional ring-array concentrator furnace as a function of receiver size and collector area was analyzed numerically and compared to that of the medium size solar furnace. For a 5.68 mm diameter spherical receiver and large collection area varying from 3.14 m2 to 100 m2, 1.1 times gradual enhancement in the maximum attainable temperature was calculated for the ring array concentrator furnace. More importantly, its average and minimum temperatures were significantly improved by 870 K and 1140 K, respectively, as compared to that of the medium size solar furnace. In addition, the three-dimensional ring-array concentrator also presented a significant tracking error compensation capacity in relation to that with the medium size solar furnace.publishe

Side-pumped continuous-wave Nd:YAG solar laser with 5.4% slope efficiency

The fellowship grants PD/BD/128267/2016, PD/BD/142827/2018, SFRH/BPD/125116/2016 of B.D.The authors report here a significant progress in side-pumped solar laser slope efficiency by pumping a 3.0 mm diameter, 30 mm length Nd:YAG single-crystal laser rod through a heliostat-parabolic mirror solar energy collection and concentration system with 0.9 m2 effective collection area. A large fused silica aspheric lens allowed an efficient focusing of the concentrated solar power from the focal zone of the parabolic mirror into the laser rod mounted within a novel two-dimensional semi-cylindrical pump cavity. 15.3 W continuous-wave 1064 nm solar laser power was measured, resulting in 5.40% slope efficiency and 2.43% solar-to-laser conversion efficency, being 2.08 and 2.30 times, respectively, more than the previous records by side-pumping configuration. The 5.40% slope efficiency is also 1.08 times more than the previous record with Nd:YAG single-crystal rod by end-side-pumping approach. By adopting an asymmetric laser resonator, this novel side-pumping scheme also enabled an efficient production of high-quality solar laser beams in either TEM11 (4.0 W), TEM01 * (doughnut-shaped, 2.9 W), TEM10 (3.2 W) or TEM00 (2.8 W) mode profiles.authorsversionpublishe

Simultaneous solar laser emissions from three Nd:YAG rods within a single pump cavity

FCT-MCTES grants SFRH/BPD/125116/2016, PD/BD/142827/2018, PD/BD/128267/2016 of C. R.Vistas, D. Garcia, B. D. Tiburcio, respectively, and FCT-MCTES Junior Researcher Contract CEECIND/03081/2017 of J. Almeida are acknowledged.We report here, to the best of our knowledge, the first simultaneous emission of three continuous-wave solar laser beams by end-side-pumping three 3.0 mm diameter, 25 mm length Nd:YAG single-crystal rods within a single conical pump cavity. An aspheric fused silica lens was used to couple the concentrated solar radiation from the focal zone of a parabolic mirror with 1.0 m2 effective collection area into the laser rods within the pump cavity. 18.3 W multimode solar laser power was measured, resulting in 5.1% laser slope efficiency. 0.036 W laser beam brightness figure of merit was also achieved for each beam, being 9 times more than that of the most efficient solar laser with 32.5 W/m2 collection efficiency. Since the three laser rods were associated with their own 1064 nm output mirrors, it was possible to adjust individually both solar laser output power levels and beam qualities of the three laser beams by adopting different resonant cavity lengths, enabling potential solar laser applications.authorsversionpublishe

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

Funding Information: The FCT-MCTES fellowship grants SFRH/BPD/125116/2016, SFRH/BD/145322/2019, 2021.06172.BD, PD/BD/1428/2018, and CEECIND/03081/2017 of Cláudia R. Vistas, Miguel Catela, Hugo Costa, Dário Garcia and Joana Almeida, respectively, are acknowledged. Funding Information: This research was funded by the Science and Technology Foundation of Portuguese Ministry of Science, Technology and Higher Education (FCT-MCTES), through the strategic project UIDB/00068/2020 and the exploratory research project EXPL/FIS-OTI/0332/2021. Publisher Copyright: © 2023 by the authors.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.publishersversionpublishe

Highly efficient side-pumped solar laser with enhanced tracking-error compensation capacity

We report here a significant numerical improvement in side-pumped solar laser collection efficiency and solar-to-laser conversion efficiency, with an enhanced tracking error compensation capacity. Two side-pumped configurations, a single-rod and a dual-rod scheme were studied. The former pumped a thick laser rod with the full collection area of a parabolic mirror and the latter pumped two thin laser rods simultaneously, each rod being pumped by half of the collection area of the same concentrator. Both configurations were composed of a fused silica aspheric lens and a 2D-shaped-semicylindrical pump cavity, within which the Nd:YAG rods were mounted, allowing a tight focusing of the concentrated solar pump power from the focal spot of the heliostat–parabolic mirror solar energy collection and concentration system and an efficient pumping to the laser crystals. 42.70 W continuous-wave multimode solar laser power, corresponding to 27.37 W/m2 collection efficiency, and 3.26% solar-to-laser power conversion efficiency were numerically calculated for the single-rod scheme, being 1.55 and 1.34 times, respectively, higher than the previous state-of-the-art experimental records of side-pumped solar laser. For the dual-rod scheme, 37.72 W multimode solar laser power, corresponding to 24.18 W/m2 collection efficiency, and 2.88% solar-to-laser power conversion efficiency were numerically obtained, being 1.37 and 1.19 times, respectively, more than the previous record in side-pumping configurations. More importantly, largely enhanced brightness figure of merit, thermal performance and tracking error compensation capacity were attained by the dual-rod scheme, as compared to that of the single-rod scheme.authorsversionpublishe

Zigzag multirod laser beam merging approach for brighttem00-mode solar laser emission from a megawatt solar furnace

An alternative multirod solar laser end-side-pumping concept, based on the megawatt solar furnace in France, is proposed to significantly improve the TEM00-mode solar laser output power level and its beam brightness through a novel zigzag beam merging technique. A solar flux homogenizer was used to deliver nearly the same pump power to multiple core-doped Nd:YAG laser rods within a water-cooled pump cavity through a fused silica window. Compared to the previous multibeam solar laser station concepts for the same solar furnace, the present approach can allow the production of high-power TEM00-mode solar laser beams with high beam brightness. An average of 1.06 W TEM00-mode laser power was numerically extracted from each of 1657 rods, resulting in a total of 1.8 kW. More importantly, by mounting 399 rods at a 30◦ angle of inclination and employing the beam merging technique, a maximum of 5.2 kW total TEM00-mode laser power was numerically extracted from 37 laser beams, averaging 141 W from each merged beam. The highest solar laser beam brightness figure of merit achieved was 148 W, corresponding to an improvement of 23 times in relation to the previous experimental record.publishersversionpublishe

Ce:Nd:YAG Solar Laser with 4.5% Solar-to-Laser Conversion Efficiency

Publisher Copyright: © 2022 by the authors.The efficiency potential of a small-size solar-pumped laser is studied here. The solar laser head was composed of a fused silica aspheric lens and a conical pump cavity, which coupled and redistributed the concentrated solar radiation from the focal zone of a parabolic mirror with an effective collection area of 0.293 m2 to end-side pump a Ce (0.1 at%):Nd (1.1 at%):YAG rod of 2.5 mm diameter and 25 mm length. Optimum solar laser design parameters were found through Zemax© non-sequential ray-tracing and LASCAD™ analysis. The utilization of the Ce:Nd:YAG medium with small diameter pumped by a small-scale solar concentrator was essential to significantly enhance the end-side pump solar laser efficiency and thermal performance. For 249 W incoming solar power at an irradiance of 850 W/m2, 11.2 W multimode solar laser power was measured, corresponding to the record solar-to-laser power conversion efficiency of 4.50%, being, to the best of our knowledge, 1.22 times higher than the previous record. Moreover, the highest solar laser collection efficiency of 38.22 W/m2 and slope efficiency of 6.8% were obtained, which are 1.18 and 1.02 times, respectively, higher than the previous records. The lowest threshold solar power of a Ce:Nd:YAG solar-pumped laser is also reported here.publishersversionpublishe

Doughnut-shaped and top hat solar laser beams numerical analysis

UIDB/00068/2020Aside from the industry-standard Gaussian intensity profile, top hat and non-conventional laser beam shapes, such as doughnut-shaped profile, are ever more required. The top hat laser beam profile is well-known for uniformly irradiating the target material, significantly reducing the heat-affected zones, typical of Gaussian laser irradiation, whereas the doughnut-shaped laser beam has attracted much interest for its use in trapping particles at the nanoscale and improving mechanical performance during laser-based 3D metal printing. Solar-pumped lasers can be a cost-effective and more sustainable alternative to accomplish these useful laser beam distributions. The sunlight was collected and concentrated by six primary Fresnel lenses, six folding mirror collectors, further compressed with six secondary fused silica concentrators, and symmetrically distributed by six twisted light guides around a 5.5 mm diameter, 35 mm length Nd:YAG rod inside a cylindrical cavity. A top hat laser beam profile (Mx2 = 1.25, My2 = 1.00) was computed through both ZEMAX® and LASCAD® analysis, with 9.4 W/m2 TEM00 mode laser power collection and 0.99% solar-to-TEM00 mode power conversion efficiencies. By using a 5.8 mm laser rod diameter, a doughnut-shaped solar laser beam profile (Mx2 = 1.90, My2 = 1.00) was observed. The 9.8 W/m2 TEM00 mode laser power collection and 1.03% solar-to-TEM00 mode power conversion efficiencies were also attained, corresponding to an increase of 2.2 and 1.9 times, respectively, compared to the state-of-the-art experimental records. As far as we know, the first numerical simulation of doughnut-shaped and top hat solar laser beam profiles is reported here, significantly contributing to the understanding of the formation of such beam profiles.publishersversionpublishe

40 W Continuous Wave Ce:Nd:YAG Solar Laser through a Fused Silica Light Guide

Funding Information: Funding: This research was financially supported by Science and Technology Foundation of Portuguese Ministry of Science, Technology and Higher Education (FCT-MCTES) in the framework of the strategic project UIDB/00068/2020 and the exploratory research project EXPL/FIS-OTI/0332/2021. The solar laser research was also supported by the Solar Facilities for European Research Area–Third Phase (SFERA III), Grant Agreement No. 823802. Funding Information: Acknowledgments: The authors express their gratitude for the FCT-MCTES fellowship grants CEECIND/03081/2017, PD/BD/142827/2018, PD/BD/128267/2016, 2021.06172.BD, SFRH/BD/ 145322/2019 and SFRH/BPD/125116/2016. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.The solar laser power scaling potential of a side-pumped Ce:Nd:YAG solar laser through a rectangular fused silica light guide was investigated by using a 2 m diameter parabolic concentrator. The laser head was formed by the light guide and a V-shaped pump cavity to efficiently couple and redistribute the concentrated solar radiation from the parabolic mirror to a 4 mm diameter, 35 mm length Ce(0.1 at.%):Nd(1.1 at.%):YAG laser rod. The rectangular light guide ensured a homogeneous distribution of the solar radiation along the laser rod, allowing it to withstand highly concentrated solar energy. With the full collection area of the parabolic mirror, the maximum continuous wave (cw) solar laser power of 40 W was measured. This, to the best of our knowledge, corresponds to the highest cw laser power obtained from a Ce:Nd:YAG medium pumped by solar radiation, representing an enhancement of two times over that of the previous side-pumped Ce:Nd:YAG solar laser and 1.19 times over the highest Cr:Nd:YAG solar laser power with a rectangular light-guide. This research proved that, with an appropriate pumping configuration, the Ce:Nd:YAG medium is very promising for scaling solar laser output power to a higher level.publishersversionpublishe

Uniform and Non-Uniform Pumping Effect on Ce:Nd:YAG Side-Pumped Solar Laser Output Performance

Funding: This research was funded by Science and Technology Foundation of Portuguese Ministry of Science, Technology and Higher Education and the exploratory research project EXPL/FIS-OTI/0332/2021. This research was also funded by the Solar Facilities for European Research Area—Third Phase (SFERA III), Grant Agreement No. 823802. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.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.publishersversionpublishe