Coherent Large Mode Area (LMA) Ytterbium-doped double clad fiber is ideal for high power fiber lasers and amplifiers used in military, industrial, and medical applications. These fibers enable efficient, compact, diode pumped lasers that directly compete with traditional solid-state lasers. The fiber features a 20 micron diameter core and 400 micron diameter clad size with a low NA (0.06) core. With > 75% slope efficiency and compatibility with operating at > 1kW of CW output power, this fiber is ideal for use in high power single-mode industrial fiber lasers.