Micro- and Nano-Structured Optical Fibers - Artificial Media for Amplification of Light.
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Micro- and Nano-Structured Optical Fibers - Artificial Media for Amplification of Light. A. Tünnermann1,2, F. Röser1, T. Schreiber1, J. Limpert1, A. Liem1, M. Reich1, S. Höfer1, H. Zellmer1, J. Burghoff1 M. Will1 and S. Nolte1 1 Friedrich Schiller University Jena, Institute of Applied Physics, Max-Wien-Platz 1, D-07743 Jena, Germany 2 Fraunhofer Institute for Applied Optics and Precision Engineering, Albert-Einstein-Strasse 7, D-07745 Jena, Germany Tel.: +49-3641/807201, Fax: +49-3641/807600, E-mail: [email protected]
ABSTRACT In experiments with rare-earth-doped fibers impressively results have been demonstrated and shown that fiber lasers and amplifiers are an attractive and power scalable solid-state laser concept. With ytterbium-doped large-mode-area double-clad fibers, output powers approaching the kW-range with diffraction limited beam quality have been realized in the continuous regime. Also in the pulsed regime, even for femtosecond pulse duration average output powers in the range of 100 W have been demonstrated. Further power scaling is limited by the end facets damage, thermo-optical problems or nonlinear effects. To overcome these restrictions microstructured fibers can be used. This type of fibers has several new preferable features. In our contribution we will discuss the advantages of microstructured fibers to reduce nonlinear effects inside the fiber and the possibility to scale the output power of fiber lasers and amplifiers with excellent beam quality. We also show fiber based chirped pulse amplification system (CPASystem) with ultra short pulses, pulse energies of up to 100 µJ and high repetition rates.
INTRODUCTION The outstanding thermo-optical properties of an actively doped fiber are the main advantage which makes rare-earth-doped fiber lasers to one of the most promising high power solid-state laser concepts. Fiber based laser systems have an excellent heat dissipation due to the large ratio of surface to active volume. The refractive index profile of the active core determines the beam quality of the fiber laser or amplifier, which is therefore independent of the pump power. The beam quality is maintained even at high output powers. Further special features of fiber lasers and amplifiers are the very high single-pass gain and therefore a low laser threshold, a broad gain bandwidth, simplicity, robustness and compactness. Furthermore a high brightness conversion of highly multimode pump light into diffraction limited laser radiation is possible with ytterbiumdoped double-clad fibers [1]. The kW-level can be reached [2-5] with diffraction limited beam quality in the continuous regime because of the efficient diode pumped operation. In the last few years a dramatic increase of the output power of continuous wave (cw) ytterbium-doped fiber lasers with diffraction limited beam quality could be observed. The reason for this evolution is the availability of high brightness fiber coupled pump diodes and the availability of highly ytterbium-doped large-mode-area-fibers
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