High power Er/Yb fiber laser with very high numerical aperture pump cladding waveguide

High power Er/Yb lasers at 1.55 μm are attractive for a number of applications, for example sensors, spectroscopy and free space telecommunications. In this paper, we report a double-clad fiber, which has an Er/Yb doped core and an inner cladding waveguide suspended in air by very thin silica bridges. The massive acceptance angles, numerical aperture larger than 0.8, and the laser output power demonstrated during the course of this work clearly indicate the potential of this technology for high power fiber lasers.