Abstract

We investigated the beam quality of ytterbium-doped large-mode-area fiber amplifiers using a tunable ring cavity, that is also used in the laboratory system of GEO600 as a pre-mode-cleaner for mode filtering. Depending on the coiling diameter, more than 98 % of the output power were contained within the polarized (200:1) TEM₀₀ mode. With the high sensitivity ring cavity analysis, the beam quality improvement caused by decreasing the coiling diameter was verified, while this could not be seen within conventional M²-measurements.

© 2004 Optical Society of America