Yb-doped Aluminophosphosilicate Research Articles

Influence of Pre-Radiation and Photo-Bleaching on the Yb-Doped Fiber Laser Radiated with Gamma-ray

To improve the radiation resistance of Yb-doped fiber lasers, we investigate the influence of pre-radiation and photo-bleaching on the gamma-radiated laser’s performance. When the gamma radiation dose is within 10 krad(Si) with a radiation dose rate less than 0.4 rad(Si)/s, compared to the output power of a non-pre-radiated Yb-doped fiber laser, the pre-radiation technique could enhance the radiation resistance against gamma-ray. However, the mode instability threshold was decreased, which was caused by the cumulated radiation-induced attenuation of pre-radiation and radiation. Based on an electronic probe micro-analyzer, the Yb-doped active fiber was Yb-doped aluminophosphosilicate ternary fiber; therefore, the radiated defects were mainly hole-related defects. A laser diode centered at 532 nm was chosen as the photo-bleaching laser source, which could recover 45.2% of the radiated-induced attenuation and increase the mode instability threshold. This work demonstrates the influence of pre-radiation and photo-bleaching on the radiation resistance against the gamma-ray of Yb-doped fiber lasers, which are of significance in the design and fabrication of related fiber lasers.

Yb-doped aluminophosphosilicate fiber amplifier with 244 pm linewidth and near diffraction limited beam quality for beam combination

Yb-doped aluminophosphosilicate fiber was fabricated by the combination system of chelate precursor doping technique and the modified chemical vapor deposition system. The technical details of the fabrication process were optimized to ensure the same elemental concentration ratio of Al/P. The capability of this fiber for the beam combining application was investigated based on a narrow linewidth fiber laser system. This fiber presented the output power of 1783 W with a slope efficiency of 83.7 % and a 20 dB root-mean-square linewidth of 0.244 nm with no nonlinear effects in the laser spectrum. Near-diffraction-limited beam quality was also observed with a M2 factor less than 1.27. In conclusion, this fiber presented an attractive laser performance for beam combination through the comprehensive optimization of fabrication technique and narrow linewidth laser system.

Comparative study of γ-radiation resistance between Yb/Ce/F and Yb/P doped aluminosilicate fibers

To quantitatively compare the radiation resistance of Ytterbium/Cerium/Fluorine(Yb/Ce/F)-codoped aluminosilicate and Yb-doped aluminophosphosilicate fibers in an ionizing radiation environment, we fabricated these two kinds of samples by applying the modified chemical vapor deposition system combined with chelate precursor doping technique. When the radiation dose accumulated to 200 Gy, the radiation-induced transmission attenuation of Yb-doped aluminophosphosilicate fiber is approximately 2.8 times that of the Yb/Ce/F-codoped aluminosilicate fiber. At this dose level, the slope efficiency of Yb/Ce/F-codoped sample decreased to 1/2 of the non-radiated efficiency value, while the other sample dropped to 1/20. The results demonstrate that Yb/Ce/F-codoped fibers are much more suitable for application in a radiated environment.

10 kW-level Output power from a Tandem- pumped Yb-doped aluminophosphosilicate fiber amplifier

In this paper, we present a 10 kW-level output power fiber amplifier based on tandem-pumping. The characteristics of active fiber for amplifier stage is reported. To ensure adequate absorption of tandem pumping light in relatively short fiber length, a large-scale Yb3+ doped aluminophosphosilicate (Al2O3-P2O5-SiO2, APS) fiber with 50 μm core and 400 μm inner-clad in diameter, i.e., a 50/400 Yb-APS fiber, was theoretically designed and experimentally fabricated by using modified chemical vapor deposition system combined with chelate precursor doping technique. The measurements showed that the dopant concentration of Yb2O3, Al2O3, and P2O5 was estimated to be 0.17 mol%, 1.4 mol%, and 1.5 mol%, respectively, and the absorption coefficient of the fiber was about 0.77 dB/m at 1018 nm. The amplifier stage with this 40 m Yb-APS fiber tandem-pumped by 1018 nm fiber laser, delivered 9.82 kW laser output at 1080.08 nm with an optical-to optical efficiency of 86.8%. The knowledge of the characteristics of the Yb3+ doped APS fiber can usefully guide future design of high output power fiber amplifier based on tandem pumping.

Yb-Doped Aluminophosphosilicate Triple-Clad Laser Fiber With High Efficiency and Excellent Laser Stability

We fully demonstrated an ytterbium (Yb) doped triple-clad laser fiber with intense pump absorption, high efficiency, and laser stability. P5+/Al3+ molar ratio in the central region of fiber core was specially designed to be ∼1.08 for compensating P2O5 evaporation, while the ratio in the outer region was set as ∼0.92 for obtaining a flattened refractive index profile. Applying a two-stage deposition process, one-time collapse technique, low-temperature multi-times sintering, and suitable flow of pure POCl3 during sintering and collapsing process were instrumental in decreasing and offsetting element evaporation. Measured in an all-fiber master oscillator power amplifier configuration, the 7-m-long fiber obtained 1.39 kW near-single-mode laser output at 1079.6 nm with a slope efficiency of 85.2% and a beam quality M 2 of 1.36. Output laser spectrum with no sign of nonlinear-related peaks and a narrow 3-dB-bandwidth of ∼0.33 nm was obtained. The fiber-based laser setup was kept at the maximum power for 1 h with power degradation less than 0.21%. The results demonstrated Yb-doped aluminophosphosilicate triple-clad fiber is a highly competitive candidate for commercial high-power laser and high-power narrow-linewidth fiber laser.

Fabrication and laser performance of triple-clad Yb-doped aluminophosphosilicate fiber

Abstract We fabricated an Yb-doped triple-clad fiber consisting in adding to aluminophosphosilicate core and F300-pump cladding, low-refractive-index fluorine doped silica cladding, and demonstrated its laser performance based on an all-fiber oscillator. MCVD system, all-gas-phase chelate precursor doping technique, and a simple overcladding process were applied to make Yb-doped aluminophosphosilicate triple-clad fiber preform. Ultra-thin substrate tube and a two-stage deposition process were proposed to decrease and offset elements evaporation. The outer region of fiber core was tested with ∼1050 ppm Yb2O3, ∼10,800 ppm Al2O3, and ∼9950 ppm P2O5, while the central region was doped with ∼600 ppm Yb2O3, 8100 ppm Al2O3, and ∼7000 ppm P2O5, respectively (ppm is in molar here). Two-stage deposition process and triple-clad design results in pump absorption from Yb3+ ions about 0.67 dB/m at 915 nm. Tested in an all-fiber oscillator configuration forward-pumped by 915 nm laser diodes, 28 m-long triple-clad fiber presented 560 W laser output with optical-to-optical efficiency of 68.7%, and the corresponding beam quality M2 is ∼1.18. The results indicate all-gas-phase chelate precursor doping technique in combination with overcladding technique is potential to manufacture high power triple-clad fiber, and ultra-thin substrate tube as well as two-stage deposition process are very effective ways to decrease and offset element evaporation.

3 kW 20/400 Yb-Doped Aluminophosphosilicate Fiber With High Stability

By using the MCVD system and the all-gas-phase chelate precursor doping technique, we fabricated an Yb-doped aluminophosphosilicate fiber with 20 μm-core and 400 μm-clad in diameter, i.e., 20/400 Yb-APS fiber. The fiber core was doped with 1100 ppm Yb3+, 7200 ppm Al3+, and 8000 ppm P5+. With a molar ratio of Al/P close to 1:1, low refractive index difference and suitable numerical aperture was obtained for large-mode-area fiber design. Directly forward pumped by 976 nm laser diodes, 11-m-long 20/400 Yb-APS fiber presented 3.03 kW laser output at 1080 nm with a slope efficiency of 76.6% and beam quality M2 of ∼1.58. Up to this power level, no signs of instable beam profile, beam quality worsening, and laser power roll-over were obtained, indirectly justified no obvious mode instability in the whole laser setup. To directly characterize its power stability and photodarkening effect, the fiber laser was kept at ∼2.1 kW for over 500 min with power degradation less than 1.1%. These results indicated that the all-gas-phase chelate precursor doping technique is highly competitive for Yb-APS fiber fabrication toward high-power laser, and the fabricated fiber is very suitable for 2 kW-level or above commercial fiber laser development.

Multi-kW Yb-doped aluminophosphosilicate fiber

For directly characterizing photodarkening effects, we demonstrated long-term laser stability of a 5kW-level fiber amplifier based on a Yb-doped aluminophosphosilicate fiber with a 30µm-core and 600µm-clad. The molar ratio of Al3+/P5+ was designed to be 1.1 ± 0.05 for remarkable photodarkening suppression, suitable numerical aperture, and central dip mitigation of refractive index profile. A modified chemical vapor deposition system combined with an all-gas-phase chelate precursor doping technique was applied to fabricate this fiber, doped with 0.15mol% Yb2O3, 1.7mol% Al2O3, and 1.4mol% P2O5. Tested at a master oscillator power amplifier laser setup, the 18m-long 30/600 Yb-doped aluminophosphosilicate fiber allowed for 6.14kW aggregated pump power at 976nm, and then showed a 5.19kW laser output at 1064.4nm with a high optical-to-optical efficiency of 85.2%. Up to this power level, an output spectrum without any sign of stimulated Raman scattering and amplified spontaneous emission was obtained. The fiber amplifier setup was kept at a 5.16kW output for over 600 minutes without power degradation, justifying a remarkable suppression of photodarkening. The results indicated that the all-gas-phase chelate precursor doping technique is highly competitive for low-photodarkening Yb-doped aluminophosphosilicate fiber fabrication towards a 5kW-level commercial high-power laser.

30/900 Yb-doped Aluminophosphosilicate Fiber Presenting 6.85-kW Laser Output Pumped With Commercial 976-nm Laser Diodes

To incorporate sufficient pumping power, a large-scale Yb-doped aluminophosphosilicate (Al2O3 -P2O5-SiO2, APS) fiber with 30- μ m core and 900- μ m inner clad in diameter, i.e., a 30/900 Yb-APS fiber, was theoretically designed and experimentally fabricated by using modified chemical vapor deposition system combining with chelate precursor doping technique. Analyzed by an electron probe microanalyzer, the dopant concentration of Yb2O3, Al2O 3, and P2O5 was estimated to be 0.14 mol%, 1.1 mol%, and 1.4 mol%, respectively. Based on an all-fiberized master oscillator power-amplifier laser setup directly forward pumped by commercial 976-nm laser diodes, 6.85-kW laser output at 1079.79 nm was achieved with an optical-to-optical efficiency of 67.1%, and the beam factor of $M^{2}$ was 2.38. The results indicate that large-scale Yb-APS fiber is quite competitive for high-power fiber laser development.

Yb-doped aluminophosphosilicate ternary fiber with high efficiency and excellent laser stability

Abstract By using chelate precursor doping technique and traditional modified chemical vapor deposition system, we fabricated Yb-doped aluminophosphosilicate (Al2O3-P2O5-SiO2, ternary Yb-APS) large-mode-area fiber and reported on its laser performance. The fiber preform was doped with Al, P and Yb with concentration of ∼8000 ppm, ∼1700 ppm and ∼400 ppm in molar percent, respectively. Tested with master oscillator power amplifier system, the home-made Yb-APS fiber was found to present 1.02 kW at 1061.1 nm with a high slope efficiency of 81.2% and excellent laser stability with power fluctuation less than ±1.1% for over 10 h. Compared with Yb-doped aluminosilicate (Al2O3-SiO2, binary Yb-AS) fiber, the introduction of P2O5 effectively suppressed photodarkening effect even the P/Al ratio is much less than 1, indicating that Yb-APS fiber is a better candidate for high power fiber lasers.

Yb-Doped Aluminophosphosilicate Laser Fiber

By using modified chemical vapor deposition system combined with chelate precursor doping technique, we report on the fabrication and characterization of Yb-doped aluminophosphosilicate (Al2O3-P2O 5-SiO2) laser fiber. Based on a master oscillator power amplifier laser setup and pumped directly by 976 nm laser diodes, 3.1 kW laser at ∼1064 nm was achieved with a slope efficiency of 78.4%. Benefiting from codoped Al and P, the laser output power showed no evidence of roll-over. The linear fitting of the output power versus the pump power shows the potentiality for further power scaling. The results indicate that chelate precursor doping technique is a competitive method for rare-earth-ion-doped fiber preform fabrication, and aluminophosphosilicate host material has potentiality to develop multi-kW level laser fibers.