Rare-earth ions doped heavy metal germanium tellurite glasses for fiber lighting in minimally invasive surgery

Enhanced Emission of Tellurite Glass Doped with Pr3+/Ho3+ and Their Applications

The shielding and spectroscopic properties of Pr⁺³ and Pr³⁺/Ho³⁺-codoped tellurite glass were investigated. The intensity parameters (Ω2 = 3.24-, Ω4 = 1.64-, Ω6 = 1.10 × 10^-20 cm²) as well as the radiative lifetimes of ³F₄ + ⁵S₂ and ⁵I₆ excited states of Ho³⁺ ions were equal to 301 μs and 3.0 μs, respectively. The former value appears to be much higher than that obtained from the lifetime measurement, indicating the presence of various energy transfer processes. The NIR spectrum of Pr³⁺/Ho³⁺-co-doped tellurite glass is dominated by strong Ho³⁺: ⁵I₆ emission at around 1200 nm, being the result of the energy transfer from Pr³⁺ to Ho³⁺ ions. The shielding effectiveness of the prepared glasses showed good performance against high-energy photons. These findings suggest that the prepared glasses could be used in laser technology such as photodynamic therapy (PDT) treatment procedures and as shielding for radiation protection.

Comparative study of upconversion and photoacoustic measurements of Er3+/Yb3+ doped La2O3 phosphor under 980 nm

The Er3+/Yb3+doped La2O3 phosphor samples were synthesized by the combustion method and then photoluminescence and photoacoustic spectroscopic studies were done. Prepared samples were annealed at 800 °C, 1000 °C and 1300 °C and all samples were found in pure hexagonal phase as confirmed by XRD analysis. From FE-SEM images it is found that particle size increases with increase in annealing temperature. The frequency upconversion emission spectra of samples were recorded by exciting the sample with 980 nm diode laser and maximum emission intensity is obtained for the sample annealed at 1000 °C for 2 h. A photoacoustic cell was designed and wavelength dependent photoacoustic spectra were measured. The effect of sample storage time on radiative and non-radiative emission properties of sample was checked by measuring upconversion emission and photoacoustic spectra, simultaneously. It is observed that the emission intensity and photoacoustic signal both decreases with time. The maximum photoacoustic signal is obtained around 974 nm wavelength and it indicates its potential for photo-thermal therapy using infrared excitation.

Ultrabright single-band red upconversion luminescence in highly transparent fluorosilicate glass ceramics containing KMnF3 perovskite nanocrystals

With a specially designed composition, highly transparent Yb³⁺/Er³⁺-doped fluorosilicate glass ceramic (GC) containing KMnF₃ perovskite nanocrystals (NCs) is obtained for the first time. The rare-earth ions are preferentially accumulated in regions embedded with KMnF₃ NCs; as a result, a remarkably enhanced (by an order of magnitude) single-band red upconversion luminescence (UCL) is achieved. Absolute quantum efficiency of the red UCL, which cannot be measured in previous GCs owing to insufficiency, reaches as high as 0.10%±0.02% in the GC sample reported in this Letter. This value is even higher than that of the well-known multiband emitting β-NaYF₄:Er³⁺/Yb³⁺ NCs and widely recognized GCs containing NaYF₄:Yb³⁺/Er³⁺NCs.

Upconversion luminescence from aluminoborate glasses doped with Tb(3+), Eu(3+) and Dy(3+) under the excitation of 2.6-μm femtosecond laser pulses

We investigated the upconversion luminescence of three aluminoborate glasses doped with Tb(3+), Eu(3+), and Dy(3+) under the excitation of 2.6-μm femtosecond (fs) laser pulses. Efficient upconversion luminescence appearing in the visible light spectral region was observed in all three glasses and the emission spectra are quite similar to those obtained under single photon excitation. From the dependence of the luminescence intensity on the excitation intensity in the low excitation intensity regime, it was revealed that a four-photon process is involved in the generation of the upconversion luminescence in the Tb(3+)- and Eu(3+)-doped glasses while a mixed two- and three-photon process is involved in the Dy(3+)-doped glass. In the high excitation intensity regime, a reduction of the slope to about 1.0 was observed for all glasses. A physical mechanism based on the super saturation of the intermediate states of the rare-earth ions was employed to interpret the upconversion luminescence under the excitation of long-wavelength fs laser pulses. Significantly broadened luminescence spectra were observed in thick glasses under high excitation intensities and it can be attributed to the self-focusing of the laser beam in the thick glasses.

Simultaneous influence of Zn2+/Mg2+ on the luminescent behaviour of La2O3:Tm3+–Yb3+ phosphors

Appreciable enhancement of the UC emission bands due to incorporation of Zn²⁺ and Mg²⁺ ions in Tm³⁺–Yb³⁺ codoped La₂O₃ phosphor can be visualized from the figure.

Pr3+-doped heavy metal germanium tellurite glasses for irradiative light source in minimally invasive photodynamic therapy surgery

Pr3+-doped medium-low phonon energy heavy metal germanium tellurite (NZPGT) glasses have been fabricated and the intense multi-peak red fluorescence emissions of Pr3+ are exhibited. Judd-Ofelt parameters Ω2 = 3.14 × 10(-20)cm(2), Ω4 = 10.67 × 10(-20)cm(2) and Ω6 = 3.95 × 10(-20)cm(2) indicate a high asymmetrical and covalent environment in the optical glasses. The spontaneous emission probabilities A(ij) corresponding to the 1D2→3H4, 3P0→3H6, and 3P0→3F2 transitions are derived to be 1859.6, 6270.1 and 17276.3s(-1), respectively, and the relevant stimulated emission cross-sections σ(em) are 5.20 × 10(-21), 14.14 × 10(-21) and 126.77 × 10(-21)cm(2), confirming that the effectiveness of the red luminescence in Pr3+-doped NZPGT glasses. Under the commercial blue LED excitation, the radiant flux and the quantum yield for the red fluorescence of Pr3+ are solved to be 219μW and 11.80%, respectively. 85.24% photons of the fluorescence in the visible region are demonstrated to be located in 600-720nm wavelength range, which matches the excitation band of the most photosensitizers (PS), holding great promise for photodynamic therapy (PDT) treatment and clinical trials.

Intense red upconversion emission of Yb/Tm/Ho triply-doped tellurite glasses

By conventional melting and quenching methods, 3Yb2O3-0.2Tm2O3-xHo2O3 (wt%, x=0.2~1.2) was doped into an easily fiberized tellurite glass with composition of 78TeO2-10ZnO-12Na2O (mol%) to form YTH-TZN78 glasses. Under 976 nm excitation, the direct sensitizing effect of Yb ions (Yb→Ho) and indirect sensitizing and self-depopulating effects of Tm ions (Yb→Tm→Ho) were found to present intense red upconversion emission at 657 nm (Red, Ho:5F5→5I8) and were responsible for the absence of the usually observed 484 nm emission (Blue, Tm:1G4→3H36). Regardless of the dopant concentration of Ho ions, the intensity of the red emission at 657 nm (Red, Ho:5F5→5I8) is about three times stronger than that of the green one at 543 nm (Green, Ho:5S2→5I8). For this certain red emission at 657 nm, 0.4 wt% Ho2O3-doped YTH-TZN78 glass was found to present the highest emission intensity and is therefore determined as a promising active tellurite glass for red fiber laser development.

Multiple visible emissions by means of up-conversion process in a microstructured tellurite glass optical fiber

We present a microstructured fiber whose 9 µm diameter core consists in three concentric rings made of three active glasses having different rare earth oxide dopants, Yb3+/Er3+, Yb3+/Tm3+ and Yb3+/Pr3+, respectively. Morphological and optical characterization of the optical fiber are presented. The photoluminescence spectrum is investigated for different pumping conditions using a commercial 980 nm laser diode. Tuning of the RGB (or white light) emission is demonstrated not only by adjusting the pump power but also by using an optical iris as spatial filter which, thanks to the microstructured core, also acts as a spectral filter.