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 M<sup>2</sup> < 1.2.
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.
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.
The cost per sensing point may be reduced by networking a number of gas sensors that shares the same tunable laser and/or the same signal processing electronics. In this paper we report on the use of a frequency modulated continuous wave (FMCW) technique for addressing the remote optical fiber gas sensor arrays. The sensor network is of a ladder topology and is interrogated by a tunable external-cavity semiconductor lasers. The system performance in terms of detection sensitivity and crosstalk between sensors is investigated. By using appropriate wavelength modulation/scanning coupled with low pass filtering, the coherent interferometric noise can be reduced greatly. Computer simulation shows that an array of 20 acetylene (C<SUB>2</SUB>H<SUB>2</SUB>) gas sensors with 2000 ppm (2.5 cm gas cell, or 50 ppm.m) detection sensitivity for each sensor may be realized. A two-sensor acetylene gas detection system is experimentally demonstrated with detection sensitivity of 165 ppm/(root)Hz (2.5 cm gas cell or 4 ppm.m/(root) Hz) and crosstalk of -25 dB.
The optical fiber flow sensors for automatic measurement in oil industry are considered excellent sensing components owing to the advantages of the immunity to electromagnetic interference and intrinsic safety telemetry. But there are not many commercially fiber optic flow sensors because of the high cost and immature measuring technology. Based on the advanced technology of optical fiber magneto-optic sensor and the matured technology of turbine flow sensor, a new kind of optical fiber mass flowmeter is studied to meet a fast growing demand for measuring flow in mass units instead of volumetric units. It not only keeps on the advantages of the turbine flowmeter, such as high accuracy, large measuring range, but also reduces the effect of electromagnetic noise from the environment, improves the response characteristics in the low frequency. In this paper, the basic principles of the optical fiber mass flowmeter is presented. The design of the optical fiber magneto-optic sensor is studied in detail and the effective method for signal processing is also discussed. Experimental results show that the optical fiber magneto-optic sensor can respond to high frequency of up to 1 KHz and the measurement accuracy of rotational velocity is about 0.1%.