Proceedings Article | 28 February 2006
KEYWORDS: Glasses, Doping, Fiber lasers, Ions, Nanoparticles, Manufacturing, Particles, Fiber amplifiers, Absorption, Cladding
Fiber lasers offer substantial advantages compared to conventional solid-state lasers due to their high efficiency,
compact size, diffraction-limited beam quality, tunability, and facile thermal management. A number of important
applications require high peak powers and pulse energies, which has generated great interest in Yb-doped, large-modearea
(LMA) fibers. Liekki has pioneered a new manufacturing technology for rare-earth-doped fibers, Direct
Nanoparticle Deposition (DND), that is capable of producing fibers uniquely well suited to power scaling.
Conventional fiber fabrication methods are characterized by poor process accuracy and flexibility due to the large
particle sizes and relatively small number of deposition layers (2-10). In contrast, DND provides independent control of
the composition of hundreds of layers that make up the core, thereby allowing previously unattainable precision,
accuracy, and uniformity in the index and rare-earth-dopant profiles. DND allows the simultaneous use of both gasphase
and liquid precursors, providing unprecedented flexibility in the glass composition. Furthermore, DND enables
fabrication of fibers with extremely high rare-earth concentrations, which minimizes the required fiber length and
correspondingly raises the threshold power for nonlinear processes. Finally, the single-step, direct-deposition process
makes manufacturing of fibers rapid and cost-effective, even for fibers with large core diameters or sophisticated
geometries and dopant distributions. DND fibers have shown high conversion efficiency (low clustering), low
photodarkening, and high damage threshold. DND thus promises to revolutionize the use of fiber lasers in applications
previously restricted to bulk, solid-state lasers and to enable new applications of high-power lasers.
