The phenomenon of transverse mode instabilities (TMI) is currently the most limiting effect for the scaling of the average output power of fiber laser systems with nearly diffraction-limited beam quality. Even though a significant amount of knowledge on TMI in single-pass fiber amplifiers has been generated in the last years, relatively little is known about this effect in multi-pass amplifiers and oscillators. In this contribution TMI is experimentally investigated in a double-pass fiber amplifier, for the first time to the best of our knowledge. The TMI threshold was found to be significantly lower in the double-pass configuration than in the single-pass arrangement. Furthermore, the investigations unveiled a complex dynamic behavior of the instabilities in the double-pass fiber amplifier.

Date Published: 22 February 2017
PDF: 4 pages
Proc. SPIE 10083, Fiber Lasers XIV: Technology and Systems, 100830R (22 February 2017); doi: 10.1117/12.2252715

Published in SPIE Proceedings Vol. 10083:
Fiber Lasers XIV: Technology and Systems
Craig A. Robin; Ingmar Hartl, Editor(s)