Yb3+ doped gain guided index anti-guided fiber based on the nanoporous silica glass rod

We report a heavily Yb³⁺/Al³⁺/B³⁺/F^- co-doped high silica rod with a negative refractive index relative to pure silica. The high silica rod was fabricated from nanoporous silica rod using glass phase-separation technology. To lower the refractive index, B³⁺ and F^- were simultaneously introduced into the silica rod and the optical properties of the silica rod were investigated. The fiber preform was prepared with the rod-in-tube method by which the Yb³⁺ doped high silica rod was only used as an active core. The fiber has a core diameter of 80 μm and a cladding diameter of 400 μm. The measurements show that the Yb³⁺ in the high silica fiber core is 15856 ppm by weight, while the refractive index is 0.0024 lower than that of the inner cladding. The amplification performance of the fiber was investigated. The results indicate that nanoporous silica glass based on the glass phase-separation technology has great potential for gain-guided index anti-guided high silica fiber.

Yb3+ heavily doped photonic crystal fiber lasers prepared by the glass phase-separation technology

We report a Yb³⁺ heavily doped photonic crystal fiber with 30 μm core diameter manufactured for the first time by an alternative technique. Silica core rods with a diameter of 3 mm and a length of 280 mm were prepared by the sodium-borosilicate glass phase-separation technology. The measurements show that the fiber has an Yb³⁺ concentration of 22810 ppm by weight, and a resultant absorption of approximately 8.5 dB/m at 976 nm. The Yb³⁺ ions are distributed throughout the fiber core with an excellent homogeneity. The laser performance demonstrates a high slope efficiency of 64.5% for laser emission at 1033.4 nm and a low power threshold of 3 W within a short fiber length of 1 m. This novel approach provides an alternative means of preparing large active silica rods with high doping levels and excellent material homogeneity for large mode area fibers with complex designs.

Yb³⁺-doped large core silica fiber for fiber laser prepared by glass phase-separation technology

We report on the preparation and optical characteristics of an Yb(3+)-doped large core silica fiber with the active core prepared from nanoporous silica rod by the glass phase-separation technology. The measurements show that the fiber has an Yb(3+) concentration of 9811 ppm by weight, a low background attenuation of 0.02 dB/m, and absorption from Yb(3+) about 5.5 dB/m at 976 nm. The laser performance presents a high slope efficiency of 72.8% for laser emission at 1071 nm and a low laser threshold of 3 W within only 2.3 m fiber length. It is suggested that the glass phase-separation technology shows great potential for realizing active fibers with larger core and complex fiber designs.

Intense ultra-broadband down-conversion in co-doped oxide glass by multipolar interaction process

We report that Eu(2+) can be an efficient sensitizer for Yb(3+) and a broadband absorber for blue solar spectra in the host of oxide glass. The greenish 4f → 5d transition of Eu(2+) and the characteristic near-infrared emission of Yb(3+) were observed, with the blue-light of xenon lamp excitation. The 5d energy can be adjusted by the host and the energy transfer efficiency can be enhanced. The quantum efficiency is up to 163.8%. Given the broad excitation band, high absorption coefficient and excellent mechanical, thermal and chemical stability, this system can be useful as down-conversion layer for solar cells.