Fabrication and Spectroscopic Analysis of Yb–Tm Co-Doped Nano-Phase Separated Yttrium–Germanium–Aluminium–Phospho–Silicate Composite Glass Optical Fibers

A new class of Yb-Tm co-doped nano-phase separated yttrium germanium aluminium phospho silica composite optical fiber has been fabricated using a modified chemical vapour deposition process with a solution doping technique in order to achieve more intense up-conversion luminescence in visible region. A strong 474 nm up-conversion luminescence, along with three peaks at 364, 650 and 790 nm of Tm3+, have been detected under excitation at 975 nm. The observation of a 474 nm strong up-conversion emission in comparison with other three emission peaks is explained using energy transfer coefficient values obtained from kinetic model of energy transfer up-conversion process. The strong up-conversion emission (474 nm) of yttrium-germanium-aluminium-phospho-silica composite optical fibers compared to yttrium aluminium silicate composite fiber is detected due to the high value of third energy transfer coefficient (W-3) associated with the 474 nm emission. Tm-Yb doped nano-engineered optical fibers would be suitable for efficient power tunable 474 nm light source for several applications.