{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,24]],"date-time":"2026-02-24T01:48:01Z","timestamp":1771897681751,"version":"3.50.1"},"reference-count":55,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2024,1,8]],"date-time":"2024-01-08T00:00:00Z","timestamp":1704672000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FCT\u2014Portuguese Foundation for Science and Technology, within the scope of the project i3N","award":["UIDB\/50025\/2020"],"award-info":[{"award-number":["UIDB\/50025\/2020"]}]},{"name":"FCT\u2014Portuguese Foundation for Science and Technology, within the scope of the project i3N","award":["UIDP\/50025\/2020"],"award-info":[{"award-number":["UIDP\/50025\/2020"]}]},{"name":"FCT\u2014Portuguese Foundation for Science and Technology, within the scope of the project i3N","award":["LA\/P\/0037\/2020"],"award-info":[{"award-number":["LA\/P\/0037\/2020"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Applied Sciences"],"abstract":"<jats:p>Cr-doped Al2O3 spheres with strong red emission were produced using a simple laser processing approach with a 50 W continuous CO2 laser. Structural characterization revealed that the produced spheres were monophasic, comprising the \u03b1-Al2O3 phase. Photoluminescence (PL) studies indicated that the observed red emission originates from multiple Cr3+ optical centers being dominated by the 2E \u2192 4A2 transition (R-lines), with a further contribution from the parity and spin forbidden 2T1 \u2192 4A2 transition (R\u2032-lines). The identification of additional radiative recombination from chromium ion pairs (N-lines) evidences that the produced samples are heavily doped. As such, energy transfer processes between the different chromium optical centers are seen to take place, as suggested by the lifetime decay analysis. PL excitation revealed that the room temperature luminescence is preferentially populated via the spin-allowed 4A2 \u2192 4T2,4T1 transitions and by the parity and spin-forbidden 4A2 \u2192 2T2 (B-lines), 2T1 (R\u2032-lines),\u00a02E (R-lines). Such results demonstrate that the present synthesis method is able to deliver high-optical-quality Al2O3:Cr crystals in a fast and simple way, with potential interest for optical, sensing, or lasing applications.<\/jats:p>","DOI":"10.3390\/app14020528","type":"journal-article","created":{"date-parts":[[2024,1,8]],"date-time":"2024-01-08T06:12:58Z","timestamp":1704694378000},"page":"528","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Red-Emitting Cr3+ on \u03b1-Al2O3:Cr Spheres Obtained in Seconds Using Laser Processing"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0424-3248","authenticated-orcid":false,"given":"Joana","family":"Rodrigues","sequence":"first","affiliation":[{"name":"Physics Department and i3N, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7138-828X","authenticated-orcid":false,"given":"Alexandre Faia","family":"Carvalho","sequence":"additional","affiliation":[{"name":"Physics Department and i3N, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2178-9904","authenticated-orcid":false,"given":"Julia","family":"Zanoni","sequence":"additional","affiliation":[{"name":"Physics Department and i3N, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4376-5594","authenticated-orcid":false,"given":"Ant\u00f3nio J. S.","family":"Fernandes","sequence":"additional","affiliation":[{"name":"Physics Department and i3N, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8729-714X","authenticated-orcid":false,"given":"Florinda M.","family":"Costa","sequence":"additional","affiliation":[{"name":"Physics Department and i3N, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6945-2759","authenticated-orcid":false,"given":"Teresa","family":"Monteiro","sequence":"additional","affiliation":[{"name":"Physics Department and i3N, University of Aveiro, 3810-193 Aveiro, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2024,1,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"493","DOI":"10.1038\/187493a0","article-title":"Stimulated Optical Radiation in Ruby","volume":"187","author":"Maiman","year":"1960","journal-title":"Nature"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1151","DOI":"10.1103\/PhysRev.123.1151","article-title":"Stimulated Optical Emission in Fluorescent Solids. 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