Impact of transverse spatial-hole burning on beam quality in large-mode-area Yb-doped fibers

The beam-quality factor of an amplified spontaneous emission source based on a Yb-doped, large-mode-area (LMA), multimode fiber was found to be optimized when the gain became saturated. A model using spatially resolved gain and transverse-mode decomposition of the optical field showed that transverse spatial-hole burning (TSHB) was responsible for the observed behavior. A simplified model without TSHB failed to predict the observed behavior of beam quality. A comparison of both models shows TSHB is also critical for properly modeling beam quality in LMA fiber amplifiers. (c) 2008 Optical Society of America.