We have demonstrated a 5 kW high-power monolithic fiber amplifier employing a homemade spindle-shaped ytterbium-doped fiber (YDF) based on the main oscillator power amplifier configuration. The YDF consists of a spindle-shaped core and cladding along the fiber length, with a core/cladding diameter of 27/410 µm at both ends and 39.5/600 µm in the middle. An output power of over 5 kW and beam quality of about 1.9 and an optical-to-optical conversion efficiency of 66.6% were achieved in the amplifier under a bidirectional pump scheme. While operating at the maximum power, the laser performance was evaluated, and the transverse mode instability and stimulated Raman scattering effects were well mitigated. To the best of our knowledge, this is the highest power demonstration in a continuous-wave fiber laser employing a tapered fiber. Further power scaling is promising by optimizing the structure of the YDF.
We have demonstrated an industrial 6 kW single-stage end-pumped all-fiber laser oscillator based on a conventional large mode area ytterbium-doped fiber (YDF) with 30 μm core diameter and 600 μm inner-cladding diameter. As a result, the fiber oscillator achieved a maximum output power of 6.07 kW at a central wavelength of ∼1080 nm with a slope efficiency of ∼65.8%. The power of Raman Stoke light was 21.6 dB smaller than the signal light at the output power of 6.07 kW. For industrial application, the stimulated Raman scattering effect was further suppressed by employing a 50 μm-core delivery fiber, and no sign of dynamic transverse mode instability comes into view during the whole experiment. The power stability measurement at ∼6 kW operation was carried out for continuous 2 h, and the power fluctuation was within 0.31%. To the best of our knowledge, this is the first detailed demonstration of industrial 6 kW high-stability single-stage all-fiber laser oscillator based on conventional YDF. The results provide a significant guidance for the construction of more than 6 kW output power single-stage end-pumped all-fiber laser systems.
A novel fiber laser called an oscillating–amplifying integrated fiber laser was studied experimentally, in which the oscillating section and amplifying section share the pump between them. Based on this configuration, a 5-kW fiber laser system with optical–optical efficiency of 80.9% and
M
2
factor of 1.5 was achieved. The startup and shutdown sequence of the laser was studied in detail. When pumps of the laser were deliberately turned on in an inverted order, such as switching on/off the amplifying section before/after the oscillating section, which is normally disastrous in a classic fiber amplifier, the laser system turned out to operate stably at full power level. Thus, it is verified that there is no priority between the amplifier and the seed in this laser system. It combines the advantages of conventional fiber oscillators and fiber amplifiers, including high efficiency, high reliability, good anti-backreflection, and simple control logic.
In order to balance the mitigation of transverse mode instability and
stimulated Raman scattering effect in the high power fiber lasers, a
specially designed Yb-doped fiber, named spindle-shaped Yb-doped
fiber, was fabricated with a core/cladding diameter of 20/400 µm at
both ends and 30/600 µm in the middle. Based on this fiber, an
all-fiber laser oscillator was built and over 3 kW near-single-mode (
M
2
factor
∼
1.3
) laser was achieved with an
optical-to-optical conversion efficiency of 78.4%. While operating at
the maximum power, the transverse mode instability is well mitigated
and the stimulated Raman scattering effect is well suppressed (
>
34
d
B
lower than signal laser). Further
power scaling is promising by optimizing the structure of the Yb-doped
fiber.
The fiber laser based on oscillating-amplifying integrated structure has the potential to take into account the advantages of fiber laser oscillator and amplifier with the characteristics of strong anti-back reflected light ability and high efficiency. Here, we achieved a 3.5 kW near single-mode (M 2~1 .24) oscillating-amplifying integrated fiber laser with an active fiber length of 8 m in the oscillating section and 17.6 m in the amplifying section. While operating at the maximum power, the optical-to-optical conversion efficiency is 87.0%, and the intensity of stimulated Raman scattering is about 23.61 dB lower than the signal light. As far as we know, this is the highest output power of the oscillating-amplifying integrated fiber laser, accompanied with the best beam quality and the highest efficiency.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.