Amplification in Ytterbium-doped fibers

Abstract

Fiber lasers and amplifiers are quickly replacing conventional bulk optical devices in a variety of applications. Ytterbium-doped fibers are of particular interest in high power applications due to their numerous advantages arising from a simple electronic structure. The behavior of Ytterbium-doped fiber devices is however strongly influenced by the selection of absorption and emission wavelengths and other parameters. Careful theoretical analysis is required to optimize the performance of the fiber device and to estimate the influence of amplified spontaneous emission, photodarkening and other such phenomena.

The objective of this thesis is to study the amplification process in Ytterbium-doped fibers experimentally and theoretically, as a preliminary step to designing a high power pump source. For this purpose, a fiber laser and an amplifier operating in the continuous wave regime have been experimentally realized based on Ytterbium-doped double-clad fibers in a free-space configuration. Theoretical models of these devices have been simulated using a commercial simulation software.

The influence of various design and fiber parameters on the performance of the devices have been studied in simulations and good agreement between the results for both the fiber laser and amplifier is found.