Modal analysis of a large-mode area photonic crystal fiber amplifier using spectral-resolved imaging

摘要

We perform modal characterization on an ytterbium-doped large mode area photonic-crystal-fiber (PCF) amplifier using spatial and spectral (S~2) resolved imaging and compare results to conventional cutoff methods. We apply numerical simulations and step-index fiber experiments to calibrate our mathematical and experimental routines of our S2 imaging system. We systematically analyze higher-order-mode (HOM) content of a polarizing 40-μm core double-clad PCF amplifier with various launching and coiling configurations. We demonstrate a HOM suppression of more than - 24 dB with variance of 2.3 dB.