Pr³⁺-doped YPO₄ nanocrystal embedded into an optical fiber

Optical fiber with YPO₄:Pr³⁺ nanocrystals (NCs) is presented for the first time using the glass powder-NCs doping method. The method's advantage is separate preparation of NCs and glass to preserve luminescent and optical properties of NCs once they are incorporated into optical fiber. The YPO₄:Pr³⁺ nanocrystals were synthesized by the co-precipitation and hydrothermal methods, optimized for size (< 100 nm), shape, Pr³⁺ ions concentration (0.2 mol%), and emission lifetime. The core glass was selected from the non-silica P₂O₅-containing system with refractive index (n = 1.788) close to the NCs (n_o = 1.657, n_e = 1.838). Optical fiber was drawn by modified powder-in-tube method after pre-sintering of glass powder-YPO₄:Pr³⁺ (wt 3%) mixture to form optical fiber preform. Luminescent properties of YPO₄:Pr³⁺ and optical fiber showed their excellent agreement, including sharp Pr³⁺ emission at 600 nm (¹D₂-³H₄) and ¹D₂ level lifetime (τ = 156 ± 5 µs) under 488 nm excitation. The distribution of the YPO₄:Pr³⁺ NCs in optical fiber were analyzed by TEM-EDS in the core region (FIB-SEM-prepared). The successful usage of glass powder-NCs doping method was discussed in the aspect of promising properties of the first YPO₄:Pr³⁺ doped optical fiber as a new way to develop active materials for lasing applications, among others.