Abstract: The glass-powder-nanocrystals (NCs) method was investigated as a powerful technique to develop new optical fibers in the context of fiber lasers and amplifiers applications. The advantage of this method is the independent preparation of NCs and matrix glass, which gives full control of the crystal phase and active ion concentration of the NCs as well as the refractive index of the glass, resulting in index matching. We demonstrated the survival of YPO4:Yb3+ and Al2O3:Cr3+ NCs in defect-free short optical fibers, pointing out essential key issues like optimization of the NCs content in the core and their mixing procedure as well as densification (pressing and pre-sintering) of the core material and effective route to lower scattering losses using smaller NCs size (150 nm). The importance of avoiding secondary crystallization has been discussed in the example of embedding two different NCs in the commercial Ohara glass matrix. In developed YPO4:Yb3+ doped optical fiber, we achieved a relatively large on/off gain coefficient of about 1 dB/cm. This result makes glass-powder-doped fibers interesting for fiber sensors and promising for fiber lasers and amplifier applications after further optical quality improvement.

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