Co-doped Aluminosilicate Glasses Research Articles

Broadband Near-Infrared Emission from Bi/Cr Co-Doped Aluminosilicate Glasses.

Bismuth-doped aluminosilicate glass has garnered significant attention due to its unique ultra-wide luminescence properties in the near-infrared (NIR) band. Enhancing the NIR luminescence of Bi-doped glass remains challenging. To achieve Bi-doped glass with more excellent luminescent properties, a series of Bi/Cr co-doped glasses were prepared, and the optical and structural properties of the samples were observed. The results indicate that low-concentration Cr doping broadens the luminescence range of Bi/Cr co-doped glass samples. The luminescence peak of Bi in the samples is at 1230 nm, while the peak of Cr is around 804 nm. The addition of an appropriate amount of Bi2O3 can enhance the NIR luminescence of Bi and Cr in the sample, realizing the energy conversion between Bi and Cr. Bi/Cr co-doped is a novel approach for achieving broadband NIR luminescence in glass materials.

Insights into enhanced broadband near-infrared emission of Bi-doped aluminosilicate glass by the addition of SnO

A series of Bi/Sn co-doped aluminosilicate glasses were prepared and the optical and structural properties of the samples were investigated. The near-infrared (NIR) luminescence properties of the glass were significantly improved by the co-doping of Bi and Sn. The NIR emission peaks of samples exhibit near 1220 nm. The addition of SnO changes the glass structure and induces a decrease in the number of negative charges in the local field of Bi, which causes the Bi valence state to change from a high valence state to a low valence state. The appropriate amount of Bi2O3 increases the number of Bi luminescent centers and realizes the transformation of the luminescent centers from Bi+ to Bi0. These results suggest that regulating the doping concentration of SnO and Bi2O3 is a convenient method to control the valence state of active ions and enhance the NIR luminescence properties of aluminosilicate glasses.

Spectroscopic investigation and heat generation of Tm3+/Ho3+-codoped aluminosilicate glasses emitting at 2.0 µm

T m 3 + / H o 3 + -codoped low silica calcium aluminosilicate (LSCAS) glasses were prepared and characterized using optical absorption, luminescence decay, and thermal lens techniques. The emission band at 2.0 µm exhibited an enhancement when the Ho concentration was increased. The luminescence quantum efficiency values were determined for both 3 F 4 and 5 I 7 levels of T m 3 + and H o 3 + ions, respectively. The high decrease of the quantum efficiency of the 3 F 4 ( T m 3 + ) level for high H o 3 + concentration evidenced efficient energy transfer processes from T m 3 + to H o 3 + . The heat generated in the energy transfer processes were estimated via a thermal lens experiment, and a rate equation model was proposed to explain the obtained result. The experimental and estimated parameters with the proposed theoretical model are in good agreement. Finally, the results of this work suggest the T m 3 + / H o 3 + -codoped LSCAS is a promising material for applications using the emission around 2.0 µm that is of great interest for biomedical applications.

Photoluminescence of Yb3+/Ce3+ co-doped aluminosilicate glasses under ultraviolet irradiation

The photoluminescence and decay properties of Yb3+/Ce3+ co-doped aluminosilicate glasses were investigated under ultraviolet irradiation. A strong excitation band was ascribed to 4f → 5d transitions of Ce3+ ions. A broad ultraviolet-visible emission band belonged to 5d → 4f transitions of Ce3+ ions and oxygen-deficient centers (ODCs) in the host matrix, and the visible-near infrared emission band was attributed to non-bridging oxygen hole centers. Comparative tests of the core composition were performed. The results showed Yb2O3 and the ODCs played a crucial role on ultraviolet-visible emission band. ODCs rather than Ce3+ ions were responsible for the 1–35 μs lifetime decay of the ultraviolet-visible emission, but had no contribution to the longer decay lifetimes (77.58 μs) for Ce-free Yb3+-doped glasses. A complex schematic energy-level diagram including the electron transfer mechanism such as Ce3+-Yb3+ → Ce4+-Yb2+, the cooperative up- and down-conversion processes was proposed to describe different luminescence mechanisms UV-expose.

Eu3+ and Ce3+ co-doped aluminosilicate glasses and transparent glass-ceramics containing gahnite nanocrystals

Transparent zinc-aluminosilicate glass-ceramics containing cerium and europium ions were prepared by controlled thermal heating of parent glasses. Addition of CeO2 resulted in the improved transparency of the glasses in the visible spectral region. X-ray diffraction patterns of the glass-ceramics indicate the formation of the crystalline gahnite phase and there are evidences of Ce3+ and Eu3+ occupancies in this phase, as well as co-existence in the amorphous phase. Ce3+ emission corresponding to the allowed f-d transitions is identified, as well as an anomalous emission in the red-infrared region. The characteristic luminescence of Eu3+ in the red is observed. Judd-Ofelt analysis of Eu3+-doped samples reveals enhanced site asymmetry around the ion and a high branching ratio for the 612 nm emission after ceramization. Due to enhanced Ce3+ emission and Eu3+ emission quenching, color tunability is possible in the red to blue spectral region, depending on the heat treatment duration.

Radiation Response Behavior of Carbon Co-Doped Aluminosilicate Glass Based Optical Fibre for Use as Radiation Sensor

Carbon co-doped alumino-silicate glass based step index multimode optical fibres (SIMM) embedded with SiC and Al4C3 crystals into silica glass were fabricated successfully through a combination of modified chemical vapour deposition (MCVD) process and solution doping technique with variation of the doping levels of carbon and Al2O3 content. The radiation response behavior of such kind of optical fibre was investigated at room temperature using Co-60-gamma radiation source of 1.25 Mev energy. Such kind of carbon alumino-silicate (CAS) glass based step index multimode (SIMM) fibre shows an excellent linear radiation response behavior with sensitivity around 0.01 dB/m/Gy at 1300 nm wavelength as well as very low recovery at room temperature which enable its practical application as radiation sensor.

Spectroscopic investigation and heat generation of Yb^3+/Ho^3+ codoped aluminosilicate glasses looking for the emission at 2 μm

Energy transfer (ET) and heat generation processes in Yb3+/Ho3+-codoped low-silica calcium aluminosilicate glasses were investigated using thermal lens (TL) and photoluminescence measurements looking for the emission around 2.0 μm. Stepwise ET processes from Yb3+ to Ho3+, upon excitation at 0.976 μm, produced highly efficient emission in the mid-infrared range at around 2.0 μm, with high fluorescence quantum efficiency (η1∼0.85 and independent of Ho3+ concentration) and relatively very low thermal loading (<0.4) for concentration up to 1.5% of Ho2O3. An equation was deduced for the description of the TL results that provided the absolute value of η1 and the number of emitted photons at 2.0 μm per absorbed pump photon by the Yb3+ ions, the latter reaching 60% for the highest Ho3+ concentration. These results suggest that the studied codoped system would be a promising candidate for the construction of photonic devices, especially for medical applications.

Enhanced White Luminescence in Mixed-Valence Eu-Doped BaAl2Si2O8 Glass Ceramics for W-LEDs

Eu3+ and Eu2+ co-doped aluminosilicate glass and glass ceramics containing BaAl2Si2O8 were prepared by melt-quenching technique in air and their luminescent properties were investigated by excitation, emission spectra and lifetime measurement. Intensities of Eu3+ and Eu2+ emissions in glass ceramics were enhanced by about 9 and 20 times compared to that in precursor glass, respectively. More interesting, under 380 nm excitation, a perfect white light with chromaticity coordinates (X = 0.333, Y = 0.307) was achieved for glass ceramics by combining intense red emission of Eu3+ with broad blue-green emission of Eu2+. Our results indicate that mixed-valence Eu-doped BaAl2Si2O8 glass ceramics may be used as potential phosphors for W-LEDs.

High power, narrow bandwidth and broadly tunable Tm 3+ , Ho 3+ -co-doped aluminosilicate glass fibre laser

A multiple-watt Tm3+, Ho3+-co-doped aluminosilicate glass fibre laser operated in narrowband (<0.5 nm) and tuned across a range exceeding 280 nm is presented. For long fibre lengths, tuning from Tm3+-dominated to Ho3+-dominated was characterised by a transition from stable pulsing to weakly modulated emission. At 2040 nm, maximum slope efficiency and average output power were 25% and 6.8 W.

Color tunability with temperature and pump intensity in Yb3+/Tm3+ codoped aluminosilicate glass under anti-Stokes excitation

Pump and thermally induced color tunabilities were demonstrated in Yb(3+)/Tm(3+) codoped low silica calcium aluminosilicate (LSCAS) glass under anti-Stokes excitation at 1.064 microm. The effects of pump intensity and sample's temperature on the upconversion emissions and mainly on the color tunabilities (from 800 to 480 nm) were investigated. The results revealed a 20- and a threefold reductions at 800/480 nm ratio as, respectively, the pump intensity and sample's temperature were increased from 27 to 700 kW/cm(2) and from 296 to 577 K. These behaviors with pump intensity and temperature (a strong increase of the 480 nm emission in comparison with the 800 nm one) were attributed to the several efficient processes occurring in the LSCAS system (Yb(3+)-->Tm(3+) energy-transfer processes, easy saturations of the Yb(3+) and Tm(3+) excited states, and radiative emissions). Besides these assigns, the temperature dependence is mainly assigned to the temperature-dependent effective absorption cross section of the ytterbium sensitizer through the so-called multiphonon-assisted anti-Stokes excitation process. Theoretical analyses and fits of the experimental data provided quantitative information.

Broad-Band Excited Quantum Cutting in Eu2 + – Yb3 + Co-doped Aluminosilicate Glasses

We report the possibility of broad-band spectral modification based on quantum cutting (QC), which converts one UV or visible photon into two near-IR photons in ion co-doped aluminosilicate glasses. Metal Al powder is added to the host glass composition to reduce to during melting in air. The existence of europium in the divalent state has been confirmed by absorption spectroscopy. Excitation and emission spectra as well as fluorescence decay measurements have been carried out to examine the occurrence of cooperative energy transfer from to ions. The QC process in this glass system enables the silicon-based solar cells to more efficiently utilize the solar energy in the broad wavelength region from 250 to 500 nm, where the silicon-based solar cells show a weak response.

Linear and non-linear optical properties of Yb 3+/Tm 3+ co-doped alumino-silicate glass prepared by sol–gel method

We report the investigations of the Yb/Tm co-doped alumino-silicate glass prepared with the sol–gel method for the linear and non-linear optical characteristics. The tetraethoxysilane (TEOS) along with other dopants in appropriate proportion were used to obtain the transparent glass with 0.65 mm thickness. The measured absorbance was used to calculate the Judd–Ofelt parameters. The emission and absorption cross-sections were calculated from the experimental measurements. The glass showed the emission around 1060 nm and 1470 nm after pumping with 980 nm, confirming the energy transfer from Yb ions to Tm ions in the silica glass. We are the first to report the Yb/Tm co-doping in the bulk silicate glass.

Fluorescence properties of divalent and trivalent europium ions in aluminosilicate glasses

Optical absorption, fluorescence, excitation and time-resolved spectra, and fluorescence dynamics were studied in Eu2+- and Eu3+-codoped aluminosilicate glasses. The results indicated that the energy transfer occurred between Eu2+ and Eu3+ ions, in which the energy corresponding to the 4f65d to S87/2 transition of Eu2+ ions caused excitation of the Eu3+ ions to the D5J level. Some of the electrons in the ground state F70 were thermally excited into the F71 state at room temperature, and thermal populations of the F70 level had great effects on the spectral shape of the D30−F72 emission. The effect of light irradiation at different wavelengths on fluorescence was systemically studied. The visible, ultraviolet and x-ray irradiation caused a decrease in the fluorescence of Eu2+ and/or Eu3+ ions. Frequency selective excitation experiments were performed at 10 K and room temperature. Instead of forming a spectral hole, the intensity of the F50−D70 transition decreased as a whole. This was attributed to the interaction of Eu3+ ions with the two-level systems existing in the glass network.

Photoinduced refractive-index change in Sm^+2/Sm^+3 codoped aluminosilicate fiber by irradiation of an Ar-ion laser

A Sm(+2)/Sm(+3) codoped aluminosilicate glass optical fiber was fabricated by use of modified chemical-vapor deposition in conjunction with an aerosol-delivery technique. A permanent index change of 7.6 x 10(-5) was induced in the fiber by irradiation of 1 W of multiline output from an Ar-ion laser. Bleaching of a broad absorption band of Sm(+2) in the visible range was also observed, and it is believed that photoionization of Sm(+2)? Sm(+3)+e plays an important role in the induced photorefractivity.