The major challenge in the development of monolithic kW class CW fiber lasers is the efficient conversion of pump
photons into a high brightness laser beam under the constraints of heat management, long term stability and
nonlinearities. This article reviews the interaction of some fiber related aspects as e.g. fiber core composition,
photodarkening and modality, as well as their influence on system complexity and power scalability. Recent work on
active fibers, pump couplers, mode field adaptors and other fiber-optic components will be presented.
High performance fibre lasers are now well established as an extremely robust and reliable technology enabling a
growing and diverse number of demanding industrial and medical and applications. Compared to rival technologies,
such as carbon-dioxide (CO2), Lamp/Diode-Pumped Solid-State (L/DPSS) and disk lasers, fibre lasers offer a number of
unique characteristics that have resulted in their wide adoption in an increasing number of industrial sectors. In addition
to replacing conventional lasers in existing applications, fibre lasers have been very successful in enabling new
applications, both factors which explain their increasing market share. In this paper we describe the basic features of
fibre lasers, and discuss their generic advantages compared with other laser technologies and consider how these may
translate to defence applications. We explain our proprietary cladding-pumping technology (GTWaveTM) and the laser
architectures we use to implement our commercial products. We present parametric performance data that show the vast
range of pulse waveforms that can be produced and discuss some new industrial applications that they have recently
enabled. Finally, we reference some of the leading research results for multi-kW continuous-wave (CW) fibre lasers and
summarise SPIE's published work in this field.
We discuss the dramatic development of high-power fiber laser technology in recent years and the prospects of kilowattclass
single-frequency fiber sources. We describe experimental results from an ytterbium-doped fiber-based multihundred-watt single-frequency, single-mode, plane-polarized master-oscillator power amplifier (MOPA) operating at 1060 nm and a similar source with 0.5 kW of output power, albeit with a degraded beam quality (M2 = 1.6) and not linearly polarized. Experiments and simulations aimed at predicting the Brillouin limit of single-frequency system with a
thermally broadened Brillouin gain are presented. These suggest that single-frequency MOPAs with over 1 kW of output power are possible. In addition, the power scalability of a simple single-strand fiber laser to 10 kW is discussed.
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.