Effective absorption in cladding-pumped fibers

Abstract

We investigate experimentally and theoretically the wavelength dependence of the pump absorption along Yb³⁺-doped fibers, for cladding-pumped single as well as coupled multimode (GTWave^TM) fibers. We show that significant spectral absorption distortions occur along the length with the 976nm absorption peak affected the most. We have developed a novel theoretical approach, based on coupled mode theory, to explain the observed effects. We have also investigated the mode mixing requirements in order to improve the absorption spectral distribution along the increase the overall absorption efficiency and discuss the implications on fiber laser performance.