Fundamental-mode operation in polarization-maintaining ytterbium-doped fiber with an effective area of 1400 micro m2

We report, for the first time to our knowledge, fundamental-mode operation in polarization-maintaining ytterbium-doped fiber with an effective area of approximately 1400 micro m(2) and birefringence of 2.1 x 10(-4). The measured critical bending radius, R(c), defined as the radius at which the loss is equal to 3 dB for 1 m of fiber, is approximately 4 cm. Lasing with slope efficiency exceeding 60% and M(2) of 1.2 has also been demonstrated.