Characterization and design of radiation-balanced Yb-doped ZBLAN fiber laser*

Thermal instability degrades laser beam quality and is a substantial hurdle in the power-scaling of fiber lasers. Radiation balancing is suggested as a viable method for heat mitigation and is based on balancing the anti-stokes fluorescence cooling against conventional sources of heating in a laser. In designing a radiation-balanced fiber laser, characterization plays a vital role. Moreover, for the laser cavity design, one needs to present a viable geometry and select the appropriate pump and signal wavelengths to achieve optimum efficiency while maintaining the radiation-balanced condition. In this study, we introduce a non-constructive and non-contact method for fully characterizing the Yb-doped ZBLAN fiber. We extract such parameters as the parasitic absorption, background absorption, quantum external efficiency, and cooling efficiency for the different pump wavelengths. We also find the optimal pump wavelength for maximum cooling efficiency.

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