Broadband Near‐Infrared Cr4+‐Doped Garnet Phosphors through Divalent Calcium Charge Compensation for Advanced Crystal Fiber Amplifiers

Near‐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. A broadband near‐infrared‐II phosphor, Y2.84AI4.9O12:0.1Cr,0.16Ca2+ (YAG:0.1Cr,0.16Ca), is optimally synthesized by the solid‐state method. YAG:0.1Cr,0.16Ca crystal fiber is sequentially fabricated by the laser‐heated pedestal growth method for light communication application. Future research should develop advanced broadband fiber amplifiers to enhance light communication.