A new 100μm aperture, 920nm laser diode chip was developed to improve fiber coupling efficiency and reliability. These chips have been assembled into single-emitter and multi-emitter packages with 105μm diameter fiber-coupled output. The single-emitter package is rated for 12W operation, while the multi-emitter package is rated at 140W. Power conversion efficiency is 50%. Over one year of accelerated active life testing has been completed along with a suite of passive, environmental qualification tests. These pumps have been integrated into 2kW, 4kW, and 6kW fiber laser engines that demonstrate excellent brightness, efficiency, and sheet metal cutting quality and speed.
We have demonstrated a monolithic (fully fused), 1.2-kW, Yb-doped fiber laser with near-single-mode beam quality.
This laser employs a new generation of high-brightness, fiber-coupled pump sources based on spatially multiplexed
single emitters, with each pump providing 100 W at 915 nm within 0.15 NA from a standard 105/125 μm fiber. The
fiber laser is end pumped through the high-reflector FBG using a 19:1 fused-fiber pump combiner, eliminating the need
for pump/signal combiners. The output wavelength is 1080 nm, with a linewidth of < 0.5 nm FWHM. A peak power of
1.5 kW was reached in modulated operation (1-ms pulse duration) with M2 < 1.2.
We have developed a commercial 4-kW fiber laser consisting of seven, 600-W modules whose outputs are combined
with a fused-fiber combiner. The system architecture has several practical advantages, including pumping with reliable
single-emitter diodes, monolithic fused-fiber construction (no free-space beams), and end pumping using a 91:1 pump
combiner (eliminating the need for complex pump/signal combiners). Typical results at 4-kW output power are a beamparameter
product of 2.6 mm-mrad, 8-hr power stability of < 0.5% rms, central wavelength of 1080 nm, and linewidth of
1.2 nm FWHM. These lasers have been incorporated into Amada machines used for cutting metal sheet and plate and
have been used to cut aluminum, mild steel, stainless steel, brass, titanium, and copper with a thickness up to 19 mm. A
world-record cutting speed of 62 m/min has been demonstrated for 1-mm aluminum sheet metal.
We report the development of fused-fiber pump and signal combiners. These combiners are enabling components of a ytterbium fiber-laser emitting 4 kW of 1080-nm radiation. The fiber-laser system consists of seven fiber laser modules and a 7:1 signal combiner. The laser modules are end-pumped by 90 915-nm JDSU L4 diode-lasers, yielding a nominal pump power of 900 W. The diode laser radiation is coupled into the laser fiber through a 91:1 fused-fiber pump combiner. The input fibers of this pump combiner are standard 105/125-um multimode fibers with an NA of 0.22. These fibers form a hexagonally packed fused-fiber bundle, which is tapered to match the cladding diameter of the laser fiber. Eighty-six percent of the light exiting the pump-combiner is emitted within an NA of 0.32, and all measurable power is emitted within an NA of 0.45. The typical insertion loss of the pump combiners is <1%. The high-brightness radiation of seven laser modules is combined into a single output fiber using a 7:1 fused-fiber signal combiner providing a total power of >4 kW in the single output beam. The beam parameter product of the combined output was 2.5 mm-mrad. The low insertion loss of < 2% indicates that the signal combiner is suitable to handle even higher laser powers.
A new type of optical pulse shaper for arbitrary waveform generation is demonstrated, based on fiber Bragg grating and micro-electro-mechanical system (MEMS) technologies. This is an on-chip device which is compact, robust, monolithic, and programmable and can be used for a variety of applications such as higher order dispersion compensation in fiber communication links and high-energy pulse amplification.