Huan Zhan

Research progress of chelate precursor doping method to fabricate Yb-doped large-mode-area silica fibers for kW-level laser

With continuous efforts and practical managing experiences, the chelate precursor doping method has been justified as an effective way to dope rare-earth ions into silica host materials, a key technique in making large-mode-area silica fibers for high power laser applications. It is characterized by good controllability, stability and repeatability to accomplish different refractive index profiles. Different preforms with a large core, designed refractive index profile, good symmetrical shape and homogeneous elemental distribution were successfully fabricated. The home-made standard 20/400-type double-cladding Yb-doped large-mode-area silica fiber was drawn and presented a 1.6 kW laser output at 1064 nm, the highest power record publically reported with this method. With further optimization, chelate precusor doping method has potential to manufacture high power laser fibers for the next generation.

5kW GTWave fiber amplifier directly pumped by commercial 976nm laser diodes.

With home-made fiber perform and special fiber drawing & coating technique, a new-type of (3 + 1) GTWave fiber theoretically designed for bi-directional pump method, was successfully fabricated and justified of integrating multi-kW pump energy from commercial 976nm laser diodes. This (3 + 1) GTWave fiber amplifier demonstrated uniform absorption of pump light and easy thermal management characteristics along the whole fiber length. This amplifier is capable of simultaneously aggregating 5.19kW pump power at 976nm and finally generating 5.07kW laser output at 1066.5nm with an optical-to-optical efficiency of 74.5%, the first publically-reported multi-kW GTWave fiber directly pumped with commercial 976nm laser diodes to the best of our knowledge. No power roll-over was found at 5kW level and further power scaling can be expected with more pump power. The results indicate that GTWave fiber is a competitive integrated fiber device to collect enough pump energy from low-cost commercial laser diodes for multi-kW fiber laser development.

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-P2O5-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.

Fluorescence Distorted Absorption Phenomenon of Yb-doped Double-clad Laser Fiber

The influence of fluorescence on the absorption measurement of Yb-doped double-clad fiber was studied. The results show that the 976 nm fluorescence leads to a linear but slight decrease of absorption coefficient at 976 nm.

6kW GTWave Fiber Amplifier

We fabricated and reported a GTWave fiber amplifier that allowed for 8.43 kW aggregated pump power. GTWave fiber presented 6 kW laser output with optical-to-optical efficiency of 69.8% without any evidence of roll-over.

2kW (2+1) GT-wave fiber

We fabricated and reported on a (2+1) GT-wave fiber suitable for bidirectional pump method. 2.02 kW laser output with optical-to-optical efficiency of 67.8% was generated in bidirectional pump GT-wave fiber amplifier.

5kW GT-Wave Fiber

We fabricated and reported on a GT-wave fiber suitable for bidirectional pump method. 5.07 kW laser output with optical-to-optical efficiency of 74.5% was generated in bidirectional pump GT-wave fiber amplifier.

3kW Yb-doped Aluminophosphosilicate Laser Fiber

We fabricated and reported on Yb-doped aluminophosphosilicate laser fiber with chelate precursor doping technique. 3.1 kW laser output with an optical-to-optical efficiency of 78.4% at ∼1064 nm was achieved without any evidence of roll-over.

Extra-Large-Mode-Area Few-Mode Laser Fiber

An Yb-doped extra-large-mode-area few-mode laser fiber was fabricated successfully by chelate precursor doping technique. With refractive index difference of 0.0004 and numerical aperture of 0.036, the

Single-mode large-mode-area laser fiber with ultralow numerical aperture and high beam quality

25-\mu \text{m}