100 W all fiber picosecond MOPA laser
Sheng-Ping Chen*, Hong-Wei Chen, Jing Hou, Ze-Jin Liu
College of Optoelectric Science and Engineering, National University of Defense Technology,
Changsha 410073, China.
Abstract: A high power picosecond laser is constructed in an all fiber
master oscillator power amplifier (MOPA) configuration. The seed source is
an ytterbium-doped single mode fiber laser passively mode-locked by a
semiconductor saturable absorber mirror (SESAM). It produces 20 mW
average power with 13 ps pulse width and 59.8 MHz repetition rate. A
direct amplification of this seed source encounters obvious nonlinear effects
hence serious spectral broadening at only ten watt power level. To avoid
these nonlinear effects, we octupled the repetition rate to about 478 MHz
though a self-made all fiber device before amplification. The ultimate
output laser exhibits an average power of 96 W, a pulse width of 16 ps, a
beam quality M2 of less than 1.5, and an optical conversion efficiency of
©2009 Optical Society of America
OCIS codes: (060.2320) Fiber optics amplifiers and oscillators; (140.3510) Lasers, fiber;
(140.4050) Mode-locked lasers
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The output power of continuous wave fiber lasers increased rapidly in the last decade to
almost ten thousand watt with diffraction limited beam quality . However, the average
power of ultrafast pulsed fiber lasers with picosecond or femto-second pulse duration has been
limited to a relatively lower power level, i.e. several hundred watts [2–4]. Even by using
combining technology, the average power of pulsed fiber laser system is still much lower than
continuous wave ones . The main limitation of pulsed fiber lasers to high average power is
the onset of nonlinear effects such as stimulated Raman scattering and self-phase modulation
due to the small core and long gain medium of fiber lasers. A direct method to suppress
nonlinear effects in fiber lasers is to increase the fiber core diameter and/or reduce the fiber
length, so as to decrease the power density and/or the interaction length. This method can
increase the nonlinear threshold to a certain extent, however is ultimately restricted by the
fiber fabrication technology. Further more, increase the fiber core diameter may degrade the
laser beam quality. An alternative way to suppress nonlinear effect is to upgrade the repetition
(C) 2009 OSA 21 December 2009 / Vol. 17, No. 26 / OPTICS EXPRESS 24008
#119106 - $15.00 USD Received 2 Nov 2009; revised 8 Dec 2009; accepted 10 Dec 2009; published 16 Dec 2009