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Double-clad optical fiber with a multi-ring core profile doped with thulium and holmium fabricated by Modified Chemical Vapor Deposition Chelate Doping Technology (MCVD-CDT) is presented. The measured Tm2O3 and Ho2O3 complexes' weight concentrations were 0.5% and 0.2% respectively. Numerical analyses show weakly guiding conditions and 42.2 µm of MFD LP01 at 2000 nm. The low NA numerical aperture (NA = 0.054) was obtained for the 20/250 µm core/cladding ratio optical fiber construction. The emission spectra in the range of 1.6–2.1 µm vs. the fiber length are presented. The full width at half maximum (FWHM) decreases from 318 to 270 nm for fiber lengths from 2 to 10 m. The presented fiber design is of interest for the development of new construction of optical fibers operating in the eye-safe spectral range. [ABSTRACT FROM AUTHOR]

An investigation of fluoroindate glass and fiber co-doped with Yb3+/Er3+ ions as a potential temperature sensor was assessed using the fluorescence intensity ratio (FIR) technique. Analysis of thermally coupled levels (TCLs—2H11/2 and 4S3/2), non-thermally coupled levels (non-TCLs—4F7/2 and 4F9/2), and their combination were examined. Additionally, the luminescent stability of the samples under constant NIR excitation using different density power at three different temperatures was carried out. The obtained values of absolute sensitivity (0.003 K−1—glass, 0.0019 K−1—glass fiber 2H11/2 → 4S3/2 transition) and relative sensitivity (2.05% K−1—glass, 1.64% K−1—glass fiber 4F7/2 → 4F9/2 transition), as well as high repeatability of the signal, indicate that this material could be used in temperature sensing applications. [ABSTRACT FROM AUTHOR]

Nanophosphors are widely used, especially in biological applications in the first and second biological windows. Currently, nanophosphors doped with lanthanide ions (Ln3+) are attracting much attention. However, doping the matrix with lanthanide ions is associated with a narrow luminescence bandwidth. This paper describes the structural and luminescence properties of co-doped LaPO4 nanophosphors, fabricated by the co-precipitation method. X-ray structural analysis, scanning electron microscope measurements with EDS analysis, and luminescence measurements (excitation 395 nm) of LaPO4:Eu3+/Nd3+ and LaPO4:Eu3+/Nd3+/Yb3+ nanophosphors were made and energy transfer between rare-earth ions was investigated. Tests performed confirmed the crystal structure of the produced phosphors and deposition of rare-earth ions in the structure of LaPO4 nanocrystals. In the range of the first biological window (650–950 nm), strong luminescence bands at the wavelengths of 687 nm and 698 nm (5D0 → 7F4:Eu3+) and 867 nm, 873 nm, 889 nm, 896 nm, and 907 nm (4F3/2 → 4I9/2:Nd3+) were observed. At 980 nm, 991 nm, 1033 nm (2F5/2 → 2F7/2:Yb3+) and 1048 nm, 1060 nm, 1073 nm, and 1080 nm (4F3/2 → 4I9/2:Nd3+), strong bands of luminescence were visible in the 950 nm–1100 nm range, demonstrating that energy transfer took place. [ABSTRACT FROM AUTHOR]

This work presents an analysis of the spectroscopic properties of glass and glass ceramics co-doped with Ni2+ and Er3+ ions. Spectroscopic analysis showed the embedding of nickel ions in the gamma-gallium oxide nanocrystals as a result of heat treatment of the glass samples. Analysis of the luminescence properties of the obtained samples under 940 nm and 980 nm pump excitation allowed the selection of a proper Er3+ ions concentration for further optical fiber fabrication. Measured lifetime results of glass-ceramics samples confirm energy transfer from nickel ions to erbium. In the process of drawing the optical fiber, it was possible to create a transparent nanocrystalline glass-ceramic core, as confirmed by XRD results. The produced glass-ceramic optical fiber was characterized by broadband emission in the range from 1100 nm to 1650 nm corresponding to the 3T 2 (3F) →3A 2 (3F) (Ni2+) and 4I 13/2 → 4I 15/2 (Er3+) transitions for 940 nm and 980 nm pump excitation. The Er3+ to Ni2+ ions emission intensity ratio of the fabricated glass-ceramic fiber was estimated to be 0.84 and 7.14 for 940 nm and 980 nm optical pumps, respectively. [ABSTRACT FROM AUTHOR]

Up-conversion luminescence of Er 3+ -doped oxyfluoride germanate optical fiber is observed under laser-diode excitation. The enhanced green emission line is due to 2 H 11/2 , 4 S 3/2  →  4 I 15/2 transition of Er 3+ . The integrated luminescence intensity related to 2 H 11/2 , 4 S 3/2  →  4 I 15/2 (green) and 4 F 9/2  →  4 I 15/2 (red) transitions of Er 3+ is reduced with increasing temperature. Several spectroscopic parameters of Er 3+ ions in optical fibers were determined. The spectral linewidth is reduced, whereas the maximum of emission peak is shifted to longer wavelengths with increasing fiber length. [ABSTRACT FROM AUTHOR]

Luminescence properties of Pr 3+ ions in germanate glasses modified by BaF 2 were investigated. Several luminescence bands originating to transitions from the 3 P 0 state to the lower-lying states of Pr 3+ were registered under 450 nm excitation. The spectral analysis suggests that the positions of luminescence bands and their relative intensities are changed significantly with BaF 2 content. The relative integrated luminescence intensities of 3 P 0 → 3 H 4 transition (blue) to the 3 P 0 → 3 F 2 transition (red) of Pr 3+ ions strongly depend on fluoride modifier BaF 2 in glass composition. The luminescence bands of Pr 3+ ions are shifted to shorter wavelengths with increasing BaF 2 content. [ABSTRACT FROM AUTHOR]

Spectroscopic properties of Er 3+ ions in lead-free oxyfluoride germanate glasses were studied. The absorption and luminescence spectra of Er 3+ ions were examined for glass samples with low and high BaF 2 content. From absorption spectra the bonding parameter was calculated and its value is reduced with increasing BaF 2 content. The maximum of absorption peak due to 4 I 15/2 − 2 H 11/2 hypersensitive transition is shifted to shorter wavelengths (blue shift) with increasing BaF 2 content. Luminescence spectra and their decays corresponding to main 4 I 13/2 − 4 I 15/2 laser transition of Er 3+ are also presented and discussed. Quite long-lived near-infrared luminescence of Er 3+ is observed for lead-free glass samples with low BaF 2 concentration. [ABSTRACT FROM AUTHOR]