High-power fiber lasers

Summary form only given. In the twelve years since the double-clad fiber geometry was developed at Polaroid, fiber laser powers have risen from milliwatts to over 60 W. With their high efficiency, ease of manufacture, robustness, and other desirable qualities, fiber lasers have become useful sources for applications in the graphic arts industry, materials processing, and telecommunications. Simultaneously, advanced fiber laser research is progressing rapidly at numerous institutions around the world. Research into fiber lasers of even higher power is being driven by materials-processing and military applications. The challenges include developing brighter, more powerful pumps, avoiding fiber damage, and preventing undesired nonlinear effects. Among the techniques under investigation are side-pumped schemes, large-core fibers, multiple-core fibers, and simultaneous operation at multiple wavelengths. Fiber lasers have been operated in various pulsed modes to satisfy diverse needs: modelocked to produce ultrafast pulses, Q-switched, and as an amplifier for injected pulses or data-encoded pulse trains. Relevant results including efforts to produce pulses approaching the mJ level are presented.