Yu‐Hsuan HsiaoKuan‐Chun ChenChun‐Ling ChienWen‐Tse HuangMikołaj KamińskiNatalia MajewskaSebastian MahlikGrzegorz LeniecEwa MijowskaSheng‐Lung HuangRU-SHI LIU2024-08-272024-08-272024-08-12https://scholars.lib.ntu.edu.tw/handle/123456789/720440Near-infrared-II (NIR-II) phosphors are extensively used as NIR phosphor-converted light-emitting diodes across various applications. Nonetheless, their application in fiber communication remains underexplored. Furthermore, efficiency challenges persist in developing broadband NIR crystal fiber amplifiers. A series of the Y3−yAl5−xO12:xCr,yCa2+ phosphors with boosted Cr4+ concentration via calcium charge compensation is synthesized, and the optimized sample is fabricated to crystal fibers to reveal the application of the NIR-II phosphors to fiber communication. The fabricated Cr4+-doped crystal fiber, exhibiting broadband Cr4+ emission within 1100–1600 nm, effectively covers the high-transmission loss region caused by water absorption in the telecommunication band. Comprehensive characterization and analyses of the Cr4+ are discussed. Y2.84Al4.9O12:0.1Cr,0.16Ca2+ crystal fiber, fabricated through phosphor synthesis, pellets’ production, and the laser-heated pedestal growth method, exhibits superior photoluminescence compared to the commercial Cr4+-doped Y3Al5O12 crystal fiber. Here the potential of NIR-II phosphors is highlighted in enhancing fiber communication and valuable insights for their future application are provided. © 2024 Wiley-VCH GmbH.enbroadband emissioncharge compensationcrystal fibergarnet structurenear-infrared phosphor[SDGs]SDG6[SDGs]SDG7journal article10.1002/adom.202401543