Modeling and optimization of high-power Nd/sup 3+/-Yb/sup 3+/ codoped fiber lasers

Abstract

High-power continuous-wave Nd <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> codoped fiber lasers (NYDFL) are analyzed, based on a rate-propagation equations model. The model takes into account energy transfer between Nd <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+ </sup> and Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> , as well as cross relaxation between Nd <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> ions, and contributions from high-order modes to the amplified spontaneous emission (ASE). Examples of cladding-pumped NYDFLs with distributed Bragg reflector (DBR) at either end are presented. We demonstrate the optimal laser design by considering the effects of the Nd <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> and Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> concentrations, pump wavelengths multiplexing, output mirror reflectivity, and the laser wavelength. Approximate quasi-analytical solutions are shown to be in good agreement with the exact numerical solutions of the rate equations for practical conditions