제 목 High power fiber lasers

강 사 Dr. Johan Nilsson

소 속 Optoelectronics Research Centre, University of Southampton, UK

시 간 2005년 12월 28일 수요일 오후 2시 ~ 3시

장 소 신공학관 301동 1112호



Abstract

Cladding-pumped fiber lasers and amplifiers offer a number of unique properties. These enabled the very rapid power-scaling seen in the last few years. However, there are many additional advantages, that enable the power to be combined with exceptional control of the output characteristics. Such sources promise to make a drastic difference in a range of new applications. Output powers from single mode or nearly diffraction-limited fiber lasers at wavelengths around 1.1μm, which now exceeds 1 kW are already reported. Advances in high-power multimode diode and fiber technology, combined with the inherent power-scalability of cladding-pumped fibers, lie behind this rapid progress. Compared to the telecom technology and especially erbium-doped fiber amplifiers that these high-power fiber lasers have evolved from, the most important differences in the fiber design are the use of double-clad fibers, the much larger core and inner cladding sizes that allow for the launch of high-power, large, pump beams and increases the damage threshold, as well as the use of ytterbium-doping. The high efficiency of low-loss Yb-doped fiber lasers (YDFLs) – over 80% is possible with high-quality, high-purity fabrication – means that even a 1 kW fiber laser generates no more than ~200 W of heat. This exceptionally low heat load simplifies heat-sinking. The overall efficiency is further enhanced by improvements in diode efficiency, which is currently at ~70%.

The high power and high control open up for new applications of fiber lasers. The high efficiency allows devices to be cascaded, and fibers make excellent pump sources, e.g., for bulk lasers [6]. Beam combination techniques, either coherent or incoherent, is an attractive alternative to reach even higher power levels. On a commercial standpoint, standardization of high-power fibers would enable the development of standard high-power components similarly to what was achieved in telecom, for the realization of monolithic high-power fiber sources.



강사이력

Dr. Johan Nilsson joined the ORC in 1995 as a Visiting Research Fellow, promoted to Senior Research Fellow in 1998 and to Reader in 2003. Group leader of the High Power Fibre Lasers group since 2000. Doctor of Engineering Sciences, Royal Institute of Technology, Stockholm, Sweden, 1994. Thesis title "Active optical waveguides for signal amplification". Research interests include: High power fibre lasers and amplifiers, nonlinear fibre optics, optical communications, with interests in devices in particular, but also fabrication, materials, simulations, systems, and applications aspects. Research experience: Royal Institute of Technology, Stockholm, Sweden, thesis work focused on EDFA, optical communications and guided-wave optical simulations; Samsung Electronics, Korea, Development of EDFA for WDM and CATV applications; Over 150 scientific publications, including patents, book contributions, and journal and conference papers, several of which were invited or post-deadline papers at leading international conferences; Co-founder of, and consultant to, Southampton Photonics, Inc.; Member of the Optical Society of America; Member of the technical program committees of the Advanced Solid State Photonics and Optical Amplifiers and Applications topical meetings, as well as of the Fiber Laser Systems Technology and Applications conference at Photonics West.