A multi-kilowatt high-power fibre laser with adjustable azimuthal mode output beam profile is presented for the first time. The beam properties, and applications in laser cutting and welding of various metals are presented.
Photodarkening-induced output power degradations and long-term stability in high power pulsed and CW fiber laser
MOPA systems are discussed. The studied laser systems are based on aluminosilicate single-mode Yb-doped fibers and
use the GTWave fiber technology for cladding pumping. The active fiber lengths are between 10-30m. We have tested
Yb-doped fiber amplifiers operated under both pulsed and CW mode. Using OTDR background-loss measurements we
show, for the first time, that the photodarkening-induced loss is non-uniformly distributed along the length of the active
fiber. By calculating the average inversion along the fiber length, we show that the induced loss follows closely an Yb-inversion
dependence to the power of 2. In addition we have studied the temperature dependence of the output power
variation. It is shown that increasing (decreasing) operating temperature results in decrease (increase) of the laser output
power, reaching the new equilibria over time scales of ~200hours. We also present data on the non-photodarkening SPI
fiber which is used in all SPI products.
Fibre pulsed lasers are increasingly being adopted as the laser of choice in a number of industrial applications, such as micromachining, drilling and marking. In peak-power-driven applications, such as marking, it is essential to retain high peak powers (in excess of 2.5 to 5 kW) at high repetition rates in order to achieve faster character marking and increased throughput.
High Power Fiber Lasers (HPFLs) and High Power Fiber Amplifiers (HPFAs) promise a number of benefits in terms of their high optical efficiency, degree of integration, beam quality, reliability, spatial compactness and thermal management. These benefits are driving the rapid adoption of HPFLs in an increasingly wide range of applications and power levels ranging from a few Watts, in for example analytical applications, to high-power >1kW materials processing (machining and welding) applications. This paper describes SPI’s innovative technologies, HPFL products and their performance capabilities. The paper highlights key aspects of the design basis and provides an overview of the applications space in both the industrial and aerospace domains. Single-fiber CW lasers delivering 1kW output power at 1080nm have been demonstrated and are being commercialized for aerospace and industrial applications with wall-plug efficiencies in the range 20 to 25%, and with beam parameter products in the range 0.5 to 100 mm.mrad (corresponding to M2 = 1.5 to 300) tailored to application requirements. At power levels in the 1 - 200 W range, SPI’s proprietary cladding-pumping technology, GTWaveTM, has been employed to produce completely fiber-integrated systems using single-emitter broad-stripe multimode pump diodes. This modular construction enables an agile and flexible approach to the configuration of a range of fiber laser / amplifier systems for operation in the 1080nm and 1550nm wavelength ranges. Reliability modeling is applied to determine Systems martins such that performance specifications are robustly met throughout the designed product lifetime. An extensive Qualification and Reliability-proving programme is underway to qualify the technology building blocks that are utilized for the fiber laser cavity, pump modules, pump-driver systems and thermo-mechanical management. In addition to the CW products, pulsed fiber lasers with pulse energies exceeding 1mJ with peak pulse powers of up to 50kW have been developed and are being commercialized. In all cases reducing the total “cost of ownership” for customers and end users is our primary objective.