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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]

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]

Highlights: [•] Spectroscopic properties of rare earth doubly doped lead borate glasses were investigated. [•] Luminescence of Tb3+ was successfully detected under excitation of Dy3+. [•] Luminescence of Eu3+ was successfully detected under excitation of Tb3+. [•] The energy transfer processes between rare earth ions in lead borate glass were evidenced. [Copyright &y& Elsevier]

Abstract: Luminescence properties of Tb3+–Eu3+ doubly doped lead borate glasses were investigated. Luminescence spectra were measured under different excitation wavelengths. Characteristic luminescence bands related to electronic transitions of trivalent terbium and europium ions were detected under direct excitation of Tb3+. The energy transfer from Tb3+ to Eu3+ in lead borate glass occurs through a nonradiative process with an efficiency up to 18%. The presence of energy transfer process was also confirmed by excitation spectra measurements. [Copyright &y& Elsevier]

This paper deals with broadband near-infrared luminescence properties of lead germanate glass triply doped with Yb3+/Er3+/Tm3+. Samples were excited at 800 nm and 975 nm. Their emission intensities and lifetimes depend significantly on Er3+ and Tm3+ concentrations. For samples excited at 800 nm, broadband emissions corresponding to the overlapped 3H4 → 3F4 (Tm3+) and 4I13/2 → 4I15/2 (Er3+) transitions centered at 1.45 µm and 1.5 µm was identified. Measurements of decay curves confirm reduction of 3H4 (Tm3+), 2F5/2 (Yb3+) and 4I13/2 (Er3+) luminescence lifetimes and the presence of energy-transfer processes. The maximal spectral bandwidth equal to 269 nm for the 3F4 → 3H6 transition of Tm3+ suggests that our glass co-doped with Yb3+/Er3+/Tm3+ is a good candidate for broadband near-infrared emission. The energy transfer from 4I13/2 (Er3+) to 3F4 (Tm3+) and cross-relaxation processes are responsible for the enhancement of broadband luminescence near 1.8 µm attributed to the 3F4 → 3H6 transition of thulium ions in lead germanate glass under excitation of Yb3+ ions at 975 nm. [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]

Lead borate glasses singly and doubly doped with Tm 3+ and Dy 3+ were prepared by traditional melt-quenching technique. The emission spectra of rare earths in studied glass systems were registered under different excitation wavelengths. The observed emission bands are located in the visible spectral region. They correspond to 1 D 2 → 3 F 4 (blue) and 1 G 4 → 3 H 6 (blue) transitions of Tm 3+ as well as 4 F 9/2 → 6 H 15/2 (blue), 4 F 9/2 → 6 H 13/2 (yellow) and 4 F 9/2 → 6 H 11/2 (red) transitions of Dy 3+ . Moreover, the energy transfer process from Tm 3+ to Dy 3+ was observed. The luminescence bands originating to characteristic transitions of thulium and dysprosium ions are present on emission spectra under direct excitation of Tm 3+ . Luminescence lifetimes for the excited states of Tm 3+ and Dy 3+ ions in lead borate glass were also determined based on decay measurements. The luminescence intensities and lifetimes depend significantly on the relative concentrations of the optically active dopants. [ABSTRACT FROM AUTHOR]

The effects of selective components M 2 O 3 (M=Al, Ga) on local structure, thermal and spectroscopic properties of lead phosphate glasses doped with Er 3+ ions were systematically investigated. It was found that the both oxide modifiers (Al 2 O 3 and Ga 2 O 3 ) may be classified as crystallizing agents for lead phosphate glass host. The glass transition temperatures for glass samples modified by M 2 O 3 were determined using differential scanning calorimetry. The X-ray diffraction analysis was used in order to verify the nature of lead phosphate - based systems. Near-infrared luminescence spectra corresponding to 4 I 13/2 → 4 I 15/2 transition of erbium ions were measured. The luminescence spectra of Er 3+ -doped lead phosphate glass are presented and discussed in relation to the impact of crystallizing agents M 2 O 3 (M=Al, Ga). Luminescence lifetimes for the upper 4 I 13/2 laser state of Er 3+ ions were also evaluated. [ABSTRACT FROM AUTHOR]

Abstract Fully amorphous rare earth co-doped barium gallo-germanate glasses were synthesized using the traditional melt quenching-technique. The glass systems were doped with selected pairs of rare earths Dy3+/Ce3+ and Dy3+/Tm3+ ions. To study the spectroscopic properties of gallo-germanate glasses co-doped with Dy3+ and Ln3+ (Ln = Ce, Tm) ions, the luminescence spectra and luminescence decay curves were recorded. It was observed that luminescence bands corresponding to characteristic transitions of Ln3+ (Ln = Ce, Tm) and dysprosium ions are present in the emission spectra measured under direct excitation of Ln3+. The experimental results indicate that energy transfer between dysprosium and cerium/thulium ions is effective. From the emission spectra, the Commission Internationale de I'Eclairage (CIE) chromaticity coordinates (x, y) were calculated in relation to the potential application of gallo-germanate glasses for white LEDs. It has been proved that our glass systems exhibit white emission originating from the simultaneous generation of several bands of Dy3+, Ce3+/Tm3+ under the UV-visible light excitation. Highlights • The rare earth co-doped barium gallo-germanate glasses were synthesized. • The luminescence spectra and luminescence decay curves were registered. • The energy transfer between dysprosium and cerium/thulium ions was examined. • The glass systems exhibit white emission under the UV-visible light excitation. [ABSTRACT FROM AUTHOR]

Lead borate glasses doubly doped with Dy 3+ –Tb 3+ were investigated using optical spectroscopy: photoluminescence and decay time measurements. The main green emission band due to the 5 D 4 → 7 F 5 transition of Tb 3+ was observed under excitation of Dy 3+ . The energy transfer process from Dy 3+ to Tb 3+ occurs through nonradiative processes. The energy transfer efficiencies and transfer probabilities as a function of a square of the total rare earth ions concentration using Förster method were calculated. The nonlinear behavior of the energy transfer probability and the luminescence intensity ratio for a higher concentration of acceptor was studied taking into account the possible processes: concentration quenching and partial crystallization of the lead borate glasses. [ABSTRACT FROM AUTHOR]

Series of lead-free borate glasses with different oxide modifiers and lanthanide ions were prepared. The effect of oxide modifiers MO (M = Ca, Sr, Ba) on spectroscopic properties of trivalent Ln 3+ (Ln = Eu, Er, Pr) were systematically investigated. Especially, the luminescence spectra of Ln 3+ -doped lead-free borate glasses are presented and discussed in relation to the impact of selective components (CaO, SrO and BaO). Several spectroscopic parameters, such as the fluorescence intensity ratio R/O (Eu 3+ ) and measured luminescence lifetimes for the 5 D 0 (Eu 3+ ), 4 I 13/2 (Er 3+ ) and 1 D 2 (Pr 3+ ) excited states of lanthanide ions were analyzed in details. The research proved that spectroscopic properties of trivalent Ln 3+ depend significantly on kind of presence oxide modifiers MO (M = Ca, Sr, Ba) in glass host matrices. [ABSTRACT FROM AUTHOR]