| In this work, we demonstrate how a polarization switching technique can be used to create multiple fiber ends, and allow the radiation to pass twice through each amplifying section for more efficient energy extraction. The technique uses a polarizing beam splitter combined with polarization switching in each arm of the cavity to define a ring-like cavity with multiple gain sections that can be end pumped. Polarization-maintaining double-clad rare-earth-doped fiber with slightly multi-mode core was used as the gain sections. A laser system based on the in-cavity polarization switching design has been demonstrated with maximum measured 62% slope efficiency and close to 30W output. The relatively low output power is only limited by the available pump sources. |
