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26-mJ pulse energy Q-switched large-pitch fiber laser system with excellent beam quality

: Jansen, Florian; Stutzki, Fabian; Liem, Andreas; Jauregui, Cesar; Limpert, Jens; Tünnermann, Andreas


Honea, Eric C. (Ed.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Fiber Lasers IX: Technology, Systems, and Applications : San Francisco, California, USA, January 2012
Bellingham, WA: SPIE, 2012 (Proceedings of SPIE 8237)
ISBN: 978-0-8194-8880-0
Paper 82371S
Conference "Fiber Lasers - Technology, Systems, and Applications" <9, 2012, San Francisco/Calif.>
Fraunhofer IOF ()
fiber laser; fiber amplifier; q-switching; high power; high pulse energy; photonic crystal fiber

In this work we report on what we believe is the highest pulse energy obtained from an effectively single-mode Qswitched fiber laser system to date. This result has been obtained using rare-earth-doped double-clad large-pitch fibers which are able to delocalize the higher-order transverse modes from the active region of the core. We have built an actively Q-switched oscillator consisting of a 1.3m long large-pitch fiber with a mode field diameter of 50?m. This oscillator delivered pulses with 500?J energy at a repetition rate of 5kHz. These seed pulses have been amplified in two fiber amplifiers which were pumped at 976nm. The pre-amplifier employs a 1.2m long large-pitch fiber with a mode field diameter of 80?m and delivered 3.5mJ pulse energy. Then, a 135?m core diameter large-pitch fiber was used as booster amplifier. Under high power operation the mode field diameter of this fiber is ~100?m. The setup can deliver average powers of up to 130W, resulting in 26mJ pulses with pulse durations of ~50ns. Additionally, since this is an effective single-mode laser system, the beam quality is close to the diffraction-limit.