Hsiao, Yu‐HsuanYu‐HsuanHsiaoChen, Kuan‐ChunKuan‐ChunChenChien, Chun‐LingChun‐LingChienMajewska, NataliaNataliaMajewskaKamiński, MikołajMikołajKamińskiMahlik, SebastianSebastianMahlikLeniec, GrzegorzGrzegorzLeniecMijowska, EwaEwaMijowskaHuang, Sheng‐LungSheng‐LungHuangLiu, Ru‐ShiRu‐ShiLiu2025-09-172025-09-172025-08-12https://scholars.lib.ntu.edu.tw/handle/123456789/732185Near-infrared (NIR)-II phosphor-converted light-emitting diodes (NIR-II pc-LEDs) have been extensively developed using NIR-II phosphor with commercial LEDs. However, the application of NIR-II phosphor in optical communications remains underexplored. In this work, a phosphor series of Y3−x−yAl4.9O12:0.1Cr,xCa2+,yMg2+ is simultaneously tuned with Mg2+ and Ca2+, resulting in Y2.76Al4.9O12:0.1Cr,0.16Ca2+,0.08Mg2+ (YAG:0.1Cr,0.16Ca,0.08Mg) crystal fiber, with a length of 2.65 cm and a diameter of 216.95 µm, is grown from the optimized phosphor. The fabrication process involved phosphor synthesis, pellet production, and crystal fiber growth using the laser-heated pedestal growth method. Proposed dual cations modification allowed to i) enhance NIR-II broadband emission in 1100–1600 nm by improving the structure due to the incorporation of Mg2+ ions and ii) provide additional tetrahedral sites for Cr4+ ions via Mg2+/Ca2+ introduction. The YAG:0.1Cr,0.16Ca,0.08Mg crystal fiber exhibits promoted luminescence compared with the commercial Cr4+-doped Y3Al5O12 crystal fiber, indicating its potential as a fiber amplifier in optical communications.enbroadband emissioncharge compensationcrystal fibernear-infrared phosphorsurface modification[SDGs]SDG7journal article10.1002/lpor.202501465