Alleviate photo darkening by single mode RMO fiber design

摘要

In this work we propose and demonstrate a single mode fiber design that alleviates photo darkening. The fiber design is based on a reduced signal mode to gain material overlap which is found to reduce the induced losses of PD. For the fiber, saturated photo darkening operation is observed after 1500 hours operation with less than 7 % reduction in slope efficiency from 350 W output power in Yb/Al co-doped material. Power scalability up to 5 kW of the RMO fiber design is theoretically predicted.