Design of High-Power Radiation-Balanced Silica Fiber Lasers with a Doped Core and Cladding

A model of laser cooling in a fiber with a doped cladding shows that a radiation-balanced fiber laser (RBFL) made of silica can produce substantial output powers. Bidirectional pumping is found to reduce the average temperature of the laser, enabling higher output powers while maintaining radiation-balanced operation. For a large-mode-area silica fiber doped with Yb in the core and cladding, simulations predict that output powers as large as 115 W can be achieved by bidirectionally pumping the doped cladding. This is not only slightly higher than with a Yb doped ZBLAN fiber with the same dimensions, but the temperature gradient in silica is also about half as large. Since silica is the most common host in fiber lasers, these predictions are very promising for the near-term realization of practical RBFLs.