Abbreviated Journal Title
We report the influence of higher order modes (HOMs) in large mode fibers operation in Q-switched oscillator configurations at similar to 2 mu m wavelength. S-2 measurements confirm guiding of LP11 and LP02 fiber modes in a large mode area (LMA) step-index fiber, whereas a prototype photonic crystal fiber (PCF) provides nearly single-mode performance with a small portion of light in the LP11 mode. The difference in HOM content leads to a significant difference in Q-switched oscillator performance. In the step-index fiber, the percentage of cladding light increases by 20% to > 40% with increasing pulse energy to similar to 250 mu J. We accredit this degradation to saturation of the gain in the fundamental mode leading to more light generated in the HOMs, which is eventually converted into cladding light. No such degradation is seen in PCF laser system for > 400 mu J energies.
Kadwani, Pankaj; Jollivet, Clemence; Sims, R. Andrew; Schülzgen, Axel; Shah, Lawrence; and Richardson, Martin, "Comparison of higher-order mode suppression and Q-switched laser performance in thulium-doped large mode area and photonic crystal fibers" (2012). Faculty Bibliography 2010s. 2815.