Implementation of yttrium aluminium garnet nanoparticles in active optical fibers by nanoparticle deposition approach

We demonstrated a versatile nanoparticle doping approach to holmium yttrium aluminum oxide (Ho:YAG) doped active optical fibers. The Ho:YAG nanoparticles of the hydrodynamic diameter of 234nm were implemented in a silica frit and collapsed into optical preform. The preform showed homogenous distribution of the dopants and the maximum concentration of Al³⁺, Y³⁺ and Ho³⁺ ions in the fiber core reached the values of 0.807, 0.343 and 0.027 at.% respectively. The refractive index profile followed the concentration profile of the dopants reaching the value of 1.4631. The spectrum showed a set of absorption bands characteristic for electronic transitions of Ho³⁺ ions. The most intensive absorption peat at 455nm showed the absorption of 51.01dB·m^-1 corresponding to the concentration of Ho³⁺ ions on the level of 0.062 at.%. Although the fiber background attenuation was quite high reaching the value of 3.59 dB·m^-1, it can be improved by tailoring the nanoparticle size and shape. Fiber can be used as an active element in fiber lasers. The applied nanoparticles can be simply replaced by other compositions allowing to expand the laser operation wavelength or prepare the radiosensitive fibers for detection of high energy radiation.