Aoxiang Lin

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.

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

By using the chelate precursor doping technique, we report on an ytterbium-doped aluminophosphosilicate (APS) large-mode-area fiber with ultralow numerical aperture of 0.036 and effective fundamental mode area of ∼550u2009u2009μm2. With a bend diameter of 600xa0mm, the bending loss of fundamental mode LP01 was measured to be <10-3u2009u2009dB/m, in agreement with the corresponding simulation results, while that of higher order mode LP11 is >100u2009u2009dB/m at 1080xa0nm. Measured in an all-fiber oscillator laser cavity, 592xa0W single-mode laser output was obtained at 1079.64xa0nm with high-beam quality M2 of 1.12. The results indicate that the chelate precursor doping technique is a competitive method for ultralow numerical aperture fiber fabrication, which is very suitable for developing single-mode seed lasers for high power laser systems.

Yb-doped large-mode-area laser fiber fabricated by halide-gas-phase-doping technique

In this manuscript, we designed a rare-earth-halide gas-phase-doping setup to fabricate a large-mode-area fiber for high power laser applications. YbCl3 and AlCl3 halides are evaporated, carried respectively and finally mixed with usual host gas material SiCl4 at the hot zone of MCVD system. Owing to the all-gas-phasing reaction process and environment, the home-made Yb-doped fiber preform has a homogeneous large core and modulated refractive index profile to keep high beam quality. The drawn fiber core has a small numerical aperture of 0.07 and high Yb concentration of 9500 ppm. By using a master oscillator power amplifier system, nearly kW-level (951 W) laser output power was obtained with a slope efficiency of 83.3% at 1063.8 nm, indicating the competition and potential of the halide-gas-phase-doping technique for high power laser fiber fabrication.

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.

Yb-doped LMA fiber fabrication using chelate precursor doping technique

We report on the fabrication of a kW-level Yb-doped fiber by using chelate precursor doping technique. Lasing performance was tested up to 1 kW laser output with slope efficiency of 81.8%.

Halide gas-phase-doping technique to fabricate large-mode-area laser fiber

By using rare-earth-halide gas-phase-doping technique, we fabricated Yb-doped large-mode-area fiber preform. Yb concentration is of ~9500ppmw in core area and 951W@1064nm laser output was obtained with a slope efficiency of 83.3%.

Experimental investigation on laser performance of distributed side-pumping fiber amplifier

1+1 type distributed-side pumping active fibers were fabricated. Pumped with 976nm LD, over 1kW output power was achieved at 1064nm and 581W power was launched into the coupling unit via one port.