High-power and high-brightness fiber sources

Sahu, J.K., Nilsson, J., Jeong, Y., Kim, J., Dupriez, P., Yoo, S., Boyland, A.J., Webb, A. and Payne, D.N. (2006) High-power and high-brightness fiber sources. Photonics 2006, Hyderabad, India. 13 - 16 Dec 2006.

Abstract

Over the past few years, the fiber lasers and amplifiers have advanced from low-power systems for telecommunication applications to multi kW level sources suitable for industrial applications such as materials processing. Fiber lasers offer unique characteristics that derive from the use of a waveguide and the properties of rare-earth (RE) doped glass, and have outstanding advantages, such as high brightness, high efficiency, excellent beam quality, and compactness compared to traditional gas and solid state lasers. Furthermore, the high surface-to-volume ratio of fiber gives them excellent capability of heat dissipation. With the development of cladding pumping (CP) technology based on the novel fiber geometry called double clad fiber (DCF), the output power of fiber laser has dramatically increased recently. The DCF comprises a second light-guiding section which acts as an inner cladding and surrounds the RE doped core, with dimensions much bigger than the core diameter. A multimode laser diode is launched into the inner cladding of the DCF and gets absorbed by the RE ions in the core, and through stimulated emission either amplifies a signal guided by the core or produce laser beam. The core can be single mode to generate a diffraction limited output beam of higher brightness than the pump beam. Therefore, the CP technology offers an efficient way to convert the low-brightness of powerful multimode laser diodes into high-brightness laser light with high output power. Advances in fiber manufacturing technology and availability of reliable high-power multimode diode pump sources, and the inherent power scalability of cladding-pumped fibers, has led to the recent demonstration of output power beyond 1 kW in CW with diffraction limited beam quality from ytterbium doped fiber laser operating at 1.1 µm. In this presentation, we review recent dramatic advances in high-power and high-brightness fiber based sources in the near infrared region between 0.9 - 2 µm with particular attention to various aspects of fiber technology development, from novel fiber geometries to tailoring the optical properties of RE ions in the fiber core, suitable for high power generation.

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Contributors

Author: J.K. Sahu

Author: J. Nilsson

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