Identification of Nanocrystalline Inclusions in Bismuth-Doped Silica Fibers and Preforms

Abstract

The nature of nanocrystalline inclusions and dopant distribution in bismuth-doped silicate fibers and preforms are studied by scanning and transmission electron microscopy, and energy and wavelength-dispersive X-ray microanalysis. The core compositions are Bi:SiO2, Bi:Al2O3-SiO2, Bi:GeO2-SiO2, Bi:Al2O3-GeO2-SiO2, and Bi:P2O5-Al2O3-GeO2-SiO2. Nanocrystals of metallic Bi, Bi2O3, SiO2, GeO2, and Bi4(GeO4)3 are observed in these glasses. These inclusions can be the reason for the background optical loss in bismuth-doped optical fibers. The bismuth concentration of 0.0048±0.0006 at% is directly measured in aluminosilicate optical fibers with effective laser generation (slope efficiency of 27% at room temperature).

Direct Laser Writing and Investigation of Optofluidic Elements inside Nanoporous Silicate Matrix

“…Each presented element has additional benefit because of the surrounding nanoporous medium, which can be impregnated with organic molecules [28], photosensitive [29] and rareearth [30] components, quantum dots [31] etc. in order to provide each element with unique optical properties.…”

Review of bismuth‐doped fibers used in O‐band optical amplifiers‐scientific challenges and outlook

“…Bismuth clusters in glasses can also be formed by post processing. In a bismuth‐doped pure silica fiber, the degree of bismuth clustering, measured by absorption spectra, can be increased by annealing the silica glass in air or argon atmosphere as is shown in Figure 5 48,51 . H 2 /D 2 loading treatment and subsequent thermal treatment, which reduces bismuth species BDF, can totally remove BACs 33 .…”

“…In a bismuth-doped pure silica fiber, the degree of bismuth clustering, measured by absorption spectra, can be increased by annealing the silica glass in air or argon atmosphere as is shown in Figure 5. 48,51 H 2 /D 2 loading treatment and subsequent thermal treatment, which reduces bismuth species BDF, can totally remove BACs. 33 For bismuth-doped phosphosilicate glass, the bismuth clusters can also be formed through post annealing starting at 550C, 52 which is much lower than bismuth-doped silica glass.…”

Broadband visible-to-NIR ASE from Bismuth doped optical fibers: a window towards lasing

“…Clearly, the MFD in BYGS fiber matches better its core diameter (5.22 versus 5.24 μm) than it occurs in BYPS fiber (6.33 versus 4.42 μm), which evidences better guidance (and lesser leakage outside the core) of the emission light in the former fiber. This difference may be only boosted via the effect of Rayleigh scattering 19) (scattering seems to be overall a prominent effect in BDFs 19,[22][23][24] ). Thus, weaker visible-to-NIR emission in BYPS fiber than in BYGS one becomes explainable.…”

“…In this regard, there are two challenges inherent to BDFs. The first is growth of unsaturable loss toward shorter wavelengths, most probably associated with Rayleigh scattering on Bi nano-inclusions, 19,22,23) and the second is a bottleneck in the system of BACs, arising due to the fact of relatively short fluorescence lifetimes of the centers in the visible (tens μs) as compared those characteristic to NIR wavelengths beyond 1 μm (hundreds μs), 1,13,[25][26][27][28][29][30] which complicates reaching inversion between the ground state and higher lying states of BACs (responsible for the visible emissions). Another but mainly technological problem to be addressed further is the presence of pronounceable central dip in the BDFs' RI profiles [refer to Fig.…”