Fibre lasers in the mid-infrared regime are useful for a diverse range of fields, including chemical and biomedical sensing, military applications and materials processing. This Review summarizes the different rare-earth cations and host materials used in mid-infrared fibre laser technology, and discusses the future applications and challenges for the field.

Towards high-power mid-infrared emission from a fibre laser

Material-dependent properties influencing the performance of fiber amplifiers are reviewed together with the available data for Er/sup 3+/. The major glass types potentially useful in this application are considered and compared to silica. The topics addressed include quenching processes and the solubility of rare-earth ions, transition strengths and bandwidths at the 1500-nm gain transition, and the characteristics at the 800-, 980-, and 1480-nm pump bands. Aluminum is shown to be an extremely useful codopant for silica, improving its ability to dissolve rare-earth ions and providing desirable spectroscopic properties for Er/sup 3+/. For some of the attributes considered, other glasses have advantages over Al silica, but only with respect to gain bandwidth and pumping performance at 800 nm is significantly better than expected from other glass compositions. >

Erbium-doped glasses for fiber amplifiers at 1500 nm

To utilize the excellent properties of silica (SiO2) glass for a glass laser host, neodymium‐aluminum (Nd–Al) and neodymium‐phosphorous (Nd–P) co‐doped SiO2 glasses were studied. They were prepared by plasma‐torch chemical vapor deposition (CVD). It was found that a doping level less than ten times the number of Nd for the Al co‐dopant and less than about fifteen times for the P co‐dopant was enough to remove undesirable fluorescence properties of Nd‐doped SiO2 glasses and make them suitable for laser application. The clustering Nd ions disperse well in a glass matrix and lasing fluorescence increases. The effects of the Al dopant on the density and Raman spectra were also studied to obtain structural information. On the basis of glass science and solution chemistry, the marked effects of both dopants were explained by the following model. Nd ions can be well incorporated into a SiO2 glass network through co‐dopant oxide forming a solvation shell around the Nd ions. This model leads to an expansible metho...

Aluminum or phosphorus co-doping effects on the fluorescence and structural properties of neodymium-doped silica glass

A new infrared luminescence from bismuth-doped silica glass is discovered. Spectroscopic properties of this glass are different from those of previously reported Bi2+- or Bi3+-doped glasses or crystals. Its luminescence spectrum is wide (full-width at half maximum; about 200 nm), with the peak at 1140 nm with 500 nm excitation. Absorption bands exist between the visible and near-infrared region. The lifetime of bismuth-doped silica glass is 630 µs at room temperature, which is longer than the lifetimes of Bi3+ luminescence reported previously.

https://iopscience.iop.org/article/10.1143/JJAP.40.L279/pdf

Infrared Luminescence from Bismuth-Doped Silica Glass

We take familiar inorganic oxide glasses and non-oxide glasses and the liquids from which they derive to review the current understanding of their atomic structure, ranging from the local environments of individual atoms to the long-range order which can cover many interatomic distances. The structural characteristics of important glasses and melts, like silicates, borates, alumino-silicates, halides and chalcogenides, are drawn from the results of recent spectroscopy and scattering experiments. The techniques include Nuclear Magnetic Resonance (NMR) and X-ray Absorption Fine Structure (XAFS), Neutron Scattering (NS) and Small- and Wide-angle X-ray Scattering measurements (SAXS/WAXS), and are often combined with computer simulation experiments in order to obtain detailed images of structure and diffusion in the glassy as well as in the molten state. We then review the current understanding of relaxation in glasses, liquids and polyamorphic states. This includes phenomenological models and theories of rela...

Inorganic glasses, glass-forming liquids and amorphizing solids

Cerium-activated silica (SiO2) glasses were prepared by plasma torch chemical vapor deposition (CVD). In Ce-doped SiO2 glasses, most Ce exists as Ce4+ ions; the remaining small amount of Ce3+ ions exhibits a broad fluorescence spectrum with a large Stokes shift, ∼9600 cm-1, from the excitation spectrum peak of 324 nm. Aluminum and phosphorus codoping considerably increases the Ce3+ ratio and shifts the peaks of both spectra to shorter wavelengths. P codoping is the more effective way to achieve this result and in some cases produces an absorption spectrum similar to that of a Ce-doped phosphate glass. These findings are consistent with the solvatiorn shell model for codoping, as previously proposed. To codope P, a soot remelting method was devised to deal with the highly volatile P2O5.

Preparation of Cerium-Activated Silica Glasses: Phosphorus and Aluminum Codoping Effects on Absorption and Fluorescence Properties

Preparation de verre de silice codope par Nd et Al par la methode CVD dans une torche de plasma a partir de SiCl 4 , AlCl 3 et NdCl 3 . Le point cle de cette methode est le developpement d'un nouvel appareil a saturation en AlCl 3 qui fournit en contenu de la vapeur d'AlCl 3 sans impurete. On presente les proprietes de fluorescence et d'autres proprietes physiques des verres obtenus, en vue d'application comme verres lasers

https://www.jstage.jst.go.jp/article/jcersj1950/93/1081/93_1081_498/_pdf

Takashi Handa

Papers

Aluminum or phosphorus co-doping effects on the fluorescence and structural properties of neodymium-doped silica glass

Preparation of Cerium-Activated Silica Glasses: Phosphorus and Aluminum Codoping Effects on Absorption and Fluorescence Properties

Preparation of Nd−Al co-doped SiO2 glass by plasma torch CVD and its fluorescence properties

Preparation of Cerium-Activated Silica Glasses: Phosphorus and Aluminum Codoping Effects on Absorption and Fluorescence Properties.