Search

Transparent Yb3+/Er3+ glass-ceramic was successfully obtained by the extrusion method. The extrusion of oxyfluoride tellurite-germanate glass co-doped with Yb3+ and Er3+ ions at 520 ℃ resulted in the formation of Ba0.75Er0.25F2.25 nanocrystals, leading to an increase in the upconversion (UC) emission intensity of 35 times in glass-ceramic with respect to the glass. The glass to glass-ceramic transition was confirmed by X-ray diffraction (XRD) and Transmission electron microscope (TEM). Also, the structural changes that occurred during crystallization were assessed using Fourier-transform infrared (FTIR) spectroscopy. Furthermore, the pump power and temperature UC emission dependence of glass and glass-ceramic under 976 nm laser excitation were investigated in detail. The assessments showed that i) two-phonons are involved in the UC process and ii) the temperature has a significant influence over it. The Yb3+/Er3+ codoped glass-ceramic shows relatively high Sa and Sr values in a wide temperature range from 300 to 573 K, presenting the maximal Sa value of 3.50 × 10-3 at 573 K and the maximal Sr value of 6.30 × 10-3 at 364 K. These results suggest that the glass-ceramic is a good candidate for optical applications such as luminescent thermometry. [ABSTRACT FROM AUTHOR]

LMA (Large Mode Area) optical fibers are presently under active investigation to explore their potential for generating laser action or broadband emission directly within the optical fiber structure. Additionally, a wide mode profile significantly reduces the power distribution density in the fiber cross-section, minimizing the power density, photodegradation, or thermal damage. Multi-stage deposition in the MCVD-CDT system was used to obtain the structural doping profile of the LMA fiber multi-ring core doped with Tm3+ and Tm3+/Ho3+ layer profiles. The low alumina content (Al2O3: 0.03wt%) results in low refractive index modification. The maximum concentrations of the lanthanide oxides were Tm2O3: 0.18wt % and Ho2O3: 0.15wt%. The double-clad construction of optical fiber with emission spectra in the eye-safe spectral range of (1.55–2.10 µm). The calculated LP01 Mode Field Diameter (MFD) was 69.7 µm (@ 2000 nm, and 1/e of maximum intensity), which confirms LMA fundamental mode guiding conditions. The FWHM and λmax vs. fiber length are presented and analyzed as a luminescence profile modification. The proposed structured optical fiber with a ring core can be used in new broadband optical radiation source designs. [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) luminescence of Pr3+ and Tm3+ ions in titanate‐germanate glasses has been studied for laser and fiber amplifier applications. The effect of the molar ratio GeO2:TiO2 (from 5:1 to 1:5) on spectroscopic properties of glass systems was studied by absorption, luminescence measurements, and theoretical calculations using the Judd–Ofelt theory. It was found that independent of the TiO2 concentration, intense NIR emissions at 1.5 and 1.8 μm were observed for glasses doped with Pr3+ and Tm3+ ions, respectively. Moreover, several spectroscopic and NIR laser parameters for Pr3+ and Tm3+ ions, such as emission bandwidth, stimulated emission cross‐section, quantum efficiency, gain bandwidth, and figure of merit, were determined. The results were discussed in detail and compared to the different laser glasses. Systematic investigations indicate that Pr3+‐doped system with GeO2:TiO2 = 2:1 and Tm3+‐doped glass with GeO2:TiO2 = 1:2 present profit laser parameters and could be successfully applied to NIR lasers and broadband optical amplifiers. [ABSTRACT FROM AUTHOR]

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]