Competence Center for Specialty Optical Fibers

Based on a special large-pitch architecture which already proved its single-mode single-polarization behavior in a passive configuration, two ytterbium-doped versions of such large-mode area fibers have been fabricated and tested in both laser and amplification configurations for high power laser source applications. Due to the high sensitivity of LPF design to the active core to passive cladding index mismatch, the realization of a single-polarization structure is highly challenging. However, we report on the preservation of a polarization-maintaining feature. A linear polarization with an extinction ratio of 17 dB is demonstrated for mode field diameters reaching up to 58 µm as long as the singlemodeness of the emitted signal is preserved.