Large mode area inverse index fiber with a graded index profile for high power single mode operation

We propose a new gain fiber structure with an inverse index profile for high power amplification of a Gaussian single mode beam. A large mode area (LMA) design can be fulfilled with the inverse index profile by implementing a graded index in the depressed core. We numerically show that the proposed gain fiber can guide a single mode Gaussian beam with a large beam area and amplify the beam to a kW level output power.