Manipulating refractive index, homogeneity and spectroscopy of Yb3+^{3+}-doped silica-core glass towards high-power large mode area photonic crystal fiber lasers

Output power scaling of single mode large mode area (LMA) photonic crystal fiber (PCF) amplifiers urgently requires the low refractive index of Yb³⁺-doped silica glasses whilst maintaining high optical homogeneity. In this paper, we report on a promising alternative Yb³⁺/Al³⁺/F¯/P⁵⁺-co-doped silica core-glass (YAFP), which is prepared by modified sol-gel method developed by our group and highly suitable for fabricating high power LMA PCF amplifiers. By controlling the doping combinations of Al³⁺/F¯/P⁵⁺ in Yb³⁺- doped silica glass,it not only ensures low refractive index (RI) but also maintains the excellent optical homogeneity and spectroscopic properties of Yb³⁺. The spectroscopic properties of Yb³⁺ ions have not deteriorated by the co-doping of F¯ and P⁵⁺ in YAFP glass compared with that of Yb³⁺/Al³⁺ co-doped silica glass. A large-size (⌀5 mm × 90 mm) YAFP silica-core glass rod with low average RI difference of 2.6 × 10¯⁴ (with respect to pure silica glass), and low radial and axial RI fluctuations of ~2 × 10¯⁴, was prepared. A LMA PCF with 50 μm core diameter was obtained by stack-capillary-draw techniques using YAFP core glass. Its core NA is 0.027. An average amplified power of 97 W peaking at 1030 nm and light-light efficiency of 54% are achieved from a 6.5 m long PCF in the pulse amplification laser experiment. Meanwhile, quasi-single-mode transmission is obtained with laser beam quality factor M² of 1.4

Improving the Laser Performance of Yb^3+-Doped Phosphate Fiber: Population Simulation of the Yb^3+ Level

Based on the Boltzmann distribution and multi-phonon relaxation probability criterion, an original Yb3+ population equation was proposed to describe the population distribution before and after laser generation, and the population distribution of Yb3+ under different pump ratios and temperatures was investigated by numerical simulation. The simulation results indicated that the laser wavelength of Yb3+-doped modified phosphate fibers have a high probability of being in the range of 1019 nm--1056 nm under the conventional pump ratio. Additionally, fibers lasing at a longer wavelength may have a lower laser threshold. For ultra-high pump ratio or high fiber temperature, the laser operation state changes from a quasi-four-level to a quasi-three-level scheme, and the laser wavelength may blue-shift. Experimental results verify the above simulation results, and in addition demonstrate an output power of 9.38 W with a slop efficiency of 27.4% in an Yb3+-doped phosphate modified fiber with a length of 35.4 cm and diameter of 280 μm from an optical path with a refrigeration patch and suppressing short-wave laser output. The results show that the laser performance of Yb3+-doped fibers can be improved by reducing the operating temperature and inhibiting short-wave laser output

Effects of F- on the optical and spectroscopic properties of Yb3+/Al3+-co-doped silica glass

Yb3+/Al3+-co-doped silica glasses with different F- content were prepared in this work by sal-gel method combined with high temperature sintering. XRF, FTIR and XPS methods were used to confirm the presence of F-. The effects of F- on the optical and spectroscopic properties of these glasses have been investigated. It is worth to notice that the F-/Si4+ mass ratio equal to 9% is a significant value showing a real change in the variation trends of numerous following parameters: refractive index, UV absorption edge, absorption and emission cross sections, scalar crystal-field N-J and fluorescent lifetimes. Furthermore, introduction of F- can adjust the refractive index of Yb3+/Al3+-co-doped silica glass and it is useful for large mode area (LMA) fibers. (C) Elsevier B.V. All rights reserved

Manipulating refractive index, homogeneity and spectroscopy of Yb3+^{3+}-doped silica-core glass towards high-power large mode area photonic crystal fiber lasers

International audienceOutput power scaling of single mode large mode area (LMA) photonic crystal fiber (PCF) amplifiers urgently requires the low refractive index of Yb 3+-doped silica glasses whilst maintaining high optical homogeneity. In this paper, we report on a promising alternative Yb 3+ /Al 3+ /F-/P 5+-co-doped silica core-glass (YAFP), which is prepared by modified sol-gel method developed by our group and highly suitable for fabricating high power LMA PCF amplifiers. By controlling the doping combinations of Al 3+ /F-/P 5+ in Yb 3+doped silica glass,it not only ensures low refractive index (RI) but also maintains the excellent optical homogeneity and spectroscopic properties of Yb 3+. The spectroscopic properties of Yb 3+ ions have not deteriorated by the co-doping of Fand P 5+ in YAFP glass compared with that of Yb 3+ /Al 3+ co-doped silica glass. A large-size (⌀5 mm × 90 mm) YAFP silica-core glass rod with low average RI difference of 2.6 × 10 −4 (with respect to pure silica glass), and low radial and axial RI fluctuations of ~2 × 10 −4 , was prepared. A LMA PCF with 50 µm core diameter was obtained by stack-capillary-draw techniques using YAFP core glass. Its core NA is 0.027. An average amplified power of 97 W peaking at 1030 nm and light-light efficiency of 54% are achieved from a 6.5 m long PCF in the pulse amplification laser experiment. Meanwhile, quasi-single-mode transmission is obtained with laser beam quality factor M 2 of 1.4