Kompetenzzentrum für optische Spezialfasern

A large-mode-area silica optical fibers with a multiring core structure co-doped with Tm3+/Ho3+ were fabricated using a modified chemical vapor deposition technique with a chelate dopant. The core consisted of alternating Al3+/Tm3+/Ho3+-doped and pure silica layers, allowing precise control of the refractive index and alumina and rare-earth distributions. Proposed construction enabled an increase in the mode-field diameter (∼26 μm) while maintaining a Gaussian beam. Moreover, optimization of the Tm3+/Ho3+ ratio in developed optical fibers enabled obtaining broadband amplified spontaneous emission due to effective Tm3+→Ho3+ energy transfer, and superposition of Tm3+ and Ho3+ emission bands. The developed fiber exhibited a 3 dB band at 151 nm and a 10 dB band exceeding 549 nm. The results demonstrated that multiring doping enables effective tailoring of the spectral and also modal properties (including beam profile) for the construction of broadband ASE sources.