{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T02:15:31Z","timestamp":1760148931423,"version":"build-2065373602"},"reference-count":42,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2023,6,20]],"date-time":"2023-06-20T00:00:00Z","timestamp":1687219200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Science and Technology Foundation of Portuguese Ministry of Science, Technology and Higher Education (FCT-MCTES)","award":["UIDB\/00068\/2020","EXPL\/FIS-OTI\/0332\/2021"],"award-info":[{"award-number":["UIDB\/00068\/2020","EXPL\/FIS-OTI\/0332\/2021"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Energies"],"abstract":"<jats:p>Significant numerical improvements in Fresnel lens Nd:YAG solar laser collection efficiency, laser quality factors and tracking error compensation capacity by two Fresnel lenses as primary solar concentrators are reported here. A Nd:YAG four-rod side-pumping configuration was investigated. The four-rod side-pumping scheme consisted of two large aspherical lenses and four semi-cylindrical pump cavities, where the Nd:YAG laser rods were placed, enabling an efficient solar pumping of the laser crystals. A 104.4 W continuous-wave multimode solar laser power was achieved, corresponding to 29.7 W\/m2 collection efficiency, which is 1.68 times that of the most efficient experimental Nd:YAG side-pumped solar laser scheme with heliostat\u2013parabolic mirror systems. End-side-pumped configuration has led to the most efficient multimode solar lasers, but it may cause more prejudicial thermal effects, poor beam quality factors and a lack of access to both rod end-faces to optimize the resonant cavity parameters. In the present work, an eight-folding-mirror laser beam merging technique was applied, aiming to attain one laser emission from the four laser rods that consist of the four-rod side-pumping scheme with a higher brightness figure of merit. A 79.8 W multimode laser output power was achieved with this arrangement, corresponding to 22.7 W\/m2. The brightness figure of merit was 0.14 W, being 1.6, 21.9 and 15.7 times that of previous experimental Nd:YAG solar lasers pumped by Fresnel lenses. A significant advance in tracking error tolerance was also numerically attained, leading to a 1.5 times enhancement in tracking error width at 10% laser power loss (TEW10%) compared to previous experimental results.<\/jats:p>","DOI":"10.3390\/en16124815","type":"journal-article","created":{"date-parts":[[2023,6,20]],"date-time":"2023-06-20T02:26:56Z","timestamp":1687228016000},"page":"4815","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Fresnel Lens Solar-Pumped Laser with Four Rods and Beam Merging Technique for Uniform and Stable Emission under Tracking Error Influence"],"prefix":"10.3390","volume":"16","author":[{"given":"Bruno D.","family":"Tib\u00farcio","sequence":"first","affiliation":[{"name":"Centro de F\u00edsica e Investiga\u00e7\u00e3o Tecnol\u00f3gica, Departamento de F\u00edsica, Faculdade de Ci\u00eancias e Tecnologia, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4406-4108","authenticated-orcid":false,"given":"Dawei","family":"Liang","sequence":"additional","affiliation":[{"name":"Centro de F\u00edsica e Investiga\u00e7\u00e3o Tecnol\u00f3gica, Departamento de F\u00edsica, Faculdade de Ci\u00eancias e Tecnologia, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5890-7623","authenticated-orcid":false,"given":"Joana","family":"Almeida","sequence":"additional","affiliation":[{"name":"Centro de F\u00edsica e Investiga\u00e7\u00e3o Tecnol\u00f3gica, Departamento de F\u00edsica, Faculdade de Ci\u00eancias e Tecnologia, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0244-8127","authenticated-orcid":false,"given":"D\u00e1rio","family":"Garcia","sequence":"additional","affiliation":[{"name":"Centro de F\u00edsica e Investiga\u00e7\u00e3o Tecnol\u00f3gica, Departamento de F\u00edsica, Faculdade de Ci\u00eancias e Tecnologia, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2888-718X","authenticated-orcid":false,"given":"Miguel","family":"Catela","sequence":"additional","affiliation":[{"name":"Centro de F\u00edsica e Investiga\u00e7\u00e3o Tecnol\u00f3gica, Departamento de F\u00edsica, Faculdade de Ci\u00eancias e Tecnologia, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0591-5309","authenticated-orcid":false,"given":"Hugo","family":"Costa","sequence":"additional","affiliation":[{"name":"Centro de F\u00edsica e Investiga\u00e7\u00e3o Tecnol\u00f3gica, Departamento de F\u00edsica, Faculdade de Ci\u00eancias e Tecnologia, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9370-1997","authenticated-orcid":false,"given":"Cl\u00e1udia R.","family":"Vistas","sequence":"additional","affiliation":[{"name":"Centro de F\u00edsica e Investiga\u00e7\u00e3o Tecnol\u00f3gica, Departamento de F\u00edsica, Faculdade de Ci\u00eancias e Tecnologia, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2023,6,20]]},"reference":[{"key":"ref_1","unstructured":"Overton, G. 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