Optimal cavity design for high-radiance, double-clad, Yb³⁺-doped fiber lasers

Abstract An analytical model for optimal cavity determination in Yb³⁺-doped double clad fiber lasers (YDFL) in free running configuration is presented. The proposed model is based on laser cavity design parameters such as pump and signal wavelengths, emission and absorption cross sections, core diameter and doping concentration. It derives the optimal cavity for maximum conversion efficiency, considering both counter propagating and co-propagating amplified spontaneous emission in the core, along with boundary conditions at the fiber facets. Results show that the model could determine an optical cavity length for Yb³⁺-doped fibers 10,000 ppm doping concentrations, 1-100 m fiber length range, core diameters between 1 and 25 μm, for different inner cladding geometries. The aim is to perform exact determination of important cavity parameters for designing efficient, diffraction limited, high-radiance optical fiber laser devices with emphasis on optimal cavity length.