Polarization-maintaining, Rod-type, Ytterbium-doped, Multi-core Fiber for High Power Operation

It has been previously observed that each core in a multi-core fiber has its own birefringence properties. Therefore, obtaining a laser output with a well-defined polarization pattern from a multi-core fiber is challenging. In this work we explain the origin of this core-dependent birefringence and present a polarization-maintaining, 35-core, fiber design that is tested in an oscillator setup, delivering over 100W of power with a polarization contrast ratio close to 10dB. This is a significant improvement with respect to a comparable non-polarization maintaining multi-core fiber.