Optical fiber lasers

Abstract

The idea of using optical fiber geometry for laser and optical amplification purposes was proposed and demonstrated in 1961 by Snitzer [1] who used a 300 μm core diameter fiber doped with neodymium as the laser active gain medium. Since the development of this laser a range of fiber lasers has been constructed using either rare earth ions [2] or optical nonlinearities [3] as the optical gain medium. Although efficient laser action has been observed from nonlinear optical fiber lasers, the greatest research emphasis has been placed on the refinement of rare earth doped systems. This has been stimulated by the observation that significant concentrations of rare earth ions could be introduced into the core of standard telecommunications grade fiber without degrading the guiding properties of the fiber [4]. Strong absorption bands are created by the rare earth ion, whilst the low loss waveguiding characteristics of the fiber are maintained at the emission wavelength of the rare earth ion. Indeed, today, rare earth doped optical fibers are an accepted and important class of laser active gain medium with a wide variety of experimental applications ranging from the remote sensing of magnetic fields [5] through to ultra-short pulse generation for coherent optical communications [6] and high resolution spectroscopy [7]. Although extensive research effort has been directed at the development of efficient erbium-doped fiber lasers for the low loss third telecommunications window of standard silica fiber at 1.55 μm [8], a selection of rare earth ions has been used as gain media giving a wavelength coverage from 0.38 μm [9] to 3.9 μm [10]. These transitions have been observed in several different types of fiber host such as silica-based fibers [11], fluorozirconate or ZBLAN fibers [12], lead germanate fibers [13], lead silicate fibers [14] and tellurite glass fibers [15].