The potential of direct nanoparticle deposition for the next generation of optical fibers

Abstract

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.

Gamma radiation effects in Yb-doped optical fiber

“…As speculated previously, this radiation resistance might be the result of the DND technology, which typically produces more uniform profiles, thus effectively dissipating energy faster and preventing the formation of color centers 17 . A further possible cause might be the presence of a Yb 2+ /Yb 3+ conversion process, which could act as an absorbing agent, thereby shielding the rest of the fiber structure from photodarkening 18 .…”

“…The spectral transmittance data showed a relatively high radiation resistance of the Yb-doped fiber under passive (not actively pumped) conditions. Fibers used in the present study were produced by Liekki using Direct Nanoparticle Deposition (DND), which can produce a more uniform doping of the rare-earth constituent than does conventional modified chemical vapor deposition 17 . Some authors have speculated that decreases in Yb clustering might be the origin of the radiation hardness exhibited by some Yb-doped fibers 17 .…”

“…Fibers used in the present study were produced by Liekki using Direct Nanoparticle Deposition (DND), which can produce a more uniform doping of the rare-earth constituent than does conventional modified chemical vapor deposition 17 . Some authors have speculated that decreases in Yb clustering might be the origin of the radiation hardness exhibited by some Yb-doped fibers 17 . A further possibility, which is known to occur in certain fluorides, is the presence of a Yb 2+ /Yb 3+ conversion process, which could effectively absorb energetic photons, thus diminishing the potential for gamma-induced color-center formation 18 .…”

Liquid Flame Spray—A Hydrogen-Oxygen Flame Based Method for Nanoparticle Synthesis and Functional Nanocoatings

“…There are also several other LFS applications related to optics, such as doped optical fiber fabrication (Rajala et al, 2003;Tammela et al, 2006), where one needs to be able to control the refractive index of the material (Becker et al, 1999). Here, aluminum, phosphorus and germanium are most often used as additives to silica.…”

Nanophosphor Coatings: Technology and Applications, Opportunities and Challenges

“…It is also industrially applied in the fabrication of optical fiber preforms (Mendez and Morse, 2007;Tammela et al, 2006). FAD is derived from flame spray pyrolysis and should be distinguished from other spray-based coating methods which could also be used for the deposition of phosphors but do not produce dispersed nanoparticles.…”