Modal properties of photonic crystal fiber for high-power 2μm fiber laser systems

Optical fibers that support single mode operation while achieving large mode areas are key elements for scaling up optical powers and pulse energies of fiber lasers. Here we report on a study of the modal properties of a new-generation of polarization maintaining large-mode-area photonic crystal fibers based on the spectrally and spatially resolved (S-2) imaging technique. A fiber designed for Tm fiber laser system single mode operation in the 2 mu m spectral range is demonstrated for coiling diameters smaller than 40cm. At shorter wavelengths in the 1.3 mu m range, efficient higher order mode suppression requires tide coiling to about 20cm diameters.