Abstract
We present a novel design of a micro-structured large-pitch, large-mode-area (LMA) asymmetric rod-type fiber. By reducing the cladding symmetry through six high-refractive index germanium-doped silica inclusions, the fiber features strong higher-order mode (HOM) delocalization, leading to a potentially enhanced preferential gain for the fundamental mode in active fibers. In addition, high resolution spatially and spectrally () resolved mode analysis measurements confirm HOM contributions below 1% and -like HOM contributions below the detection limit. This proposed fiber design enables single-mode operation, with near-diffraction-limited beam quality of and an effective mode area of at 1064 nm. This design opens new insights into improving the threshold-like onset of modal instabilities in high-power fiber lasers and fiber amplifiers by efficiently suppressing modes.
© 2017 Optical Society of America
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