Co-doped Phosphate Glass Research Articles

Down-shifting in Ce3+- Tb3+ co-doped phosphate glasses for solar cells application

The Down-Shifting (DS) of UV photons into the visible range has been attracting much attention for lighting appliances and solar cells. This work reported the DS luminescence in Ce3+-Tb3+ co-doped phosphate glasses. Photoluminescence and decay curves were measured and analysed. According to the emission spectra, it was noticed a decrease in emission of the Ce3+ peak intensity and an increase of the Tb3+ visible emission intensity when the Tb3+ concentration is enlarged, indicating an energy transfer process from Ce3+ to Tb3+. Moreover, it was observed that the blue emission of Tb3+ decreases, while the green emission enhances by gradually increasing Tb3+ concentration. According to the decay curves of Tb3+, this result can be explained by cross-relaxation between Tb3+ ions. The experimental temporal evolution of the green emission of Tb3+ ions obtained under excitation of the Ce3+ ions at 280 nm is well simulated using a proposed model. In this way, the dynamics of the processes involved is perfectly understood and can be applied for solar cell applications. Therefore, the samples were placed over a solar cell and excited with UV excitation. In this excitation range, the silicon solar cell is not efficient, but the Ce3+ ions absorb this energy and transfer to the Tb3+ ions, which produce an intense visible emission. This emission is detected by the solar cell and produces photocurrent. In summary, the use of co-doped phosphate glass could enhance the current in a solar cell in the UV region.

Er3+/ Yb3+ co-doped multi-functional silica phosphate glass films for integrated photonic applications

The multi-component silicate glasses co-doped with Er3+/Yb3+ were fabricated as thin films by the spin coating technique, which was analyzed for their optoelectronic response. Their monolith counterparts synthesized by the sol-gel route were used for the electrical studies. The films evidenced nanocristobalite phases at low levels of doping. The film micrographs explicated gas-trapped circular dimensions on the surface, due to the spreading of the sol on the substrate during the spin coating process. The glasses show a decrease in the number of polarizable non-bridging oxygen units with doping, reducing the polarizability and optical basicity. The films exhibit prominent green lasing in the downshifting process. The energy transfer from the Yb3+ ions endows the glasses with significant red lasing, suppressing the green emissions by the upconversion mechanism, which is also validated by the colorimetric chromaticity analysis. The gain cross-section of the glass doped with 1.5 mol% of Yb3+ is 23.3 × 10−20 cm2 in the S-band telecommunication domain. The glass film evidences its potential for NIR lasers, beyond a population inversion of 40 %, and a decreasing metastable lifetime of 6.6 μs. Beyond 1.5 mol% of the co-dopant Yb3+, energy transfer dominates, due to the dipole-quadrupole interactions, which has been corroborated by the Inokuti-Hirayama model. The conductivity in the glasses shows a decreasing trend with doping. The Randle's equivalent circuitry of the Nyquist impedance plots, predicts Warburg diffusion impedance that deters the space charge polarization. The consequential decrease in the dielectric constant and capacitance makes the glasses suggestive of multi-layer dielectric substrates in the integrated microelectronic technology for soldering of the printed circuit boards (PCB) that demand low signal losses.

Theoretical Studies on γ-Photon/Neutron Shielding Characteristics of RE3+Co-Doped Borate, Phosphate, and Silicate Glass Systems

The Phy-X program software was used to investigate the γ- and neutron shielding properties of trivalent rare earth co-doped borate-, phosphate- and silicate glasses (G1-G10) concerning elemental composition and density. The attenuation coefficients (μ/ρ and μ), half/tenth value layer (HVL and TVL), and mean free path (MFP) were calculated, and each revealed the influence of rare earth including the Pb, Ba, and Bi elements. Energy and compositional dependent effective atomic number (Zeff), effective electron density (Neff), and effective electron conductivity (Ceff) of all the glasses were studied. On the high-density glasses G6, G9, and G10, the HVL and TVL values are projected to be lower than on the other examined glasses. The neutron radiation shielding abilities of the studied glasses were investigated by determining removal cross-section (RCS). The results were compared to those of commercially available materials such as concrete, graphite, water, and Hematite-serpentine concrete. The γ-ray exposure buildup and energy absorption factor values (EBF/EABF) of glass samples were determined in the energy range of 0.015 to 15 MeV.

Preparation and optical properties of Dy3+/Tb3+ co-doped phosphate glasses

Preparation and optical properties of Dy3+/Tb3+ co-doped phosphate glasses

Toward a10 dB net-gain waveguide amplifier in an Er3+-Yb3+ co-doped phosphate glass.

High-gain materials and high-quality structures are the two main conditions that determine the amplification performance of optical waveguides. However, it has been hard to balance each other, to date. In this work, we demonstrate breakthroughs in both glass optical gain and optical waveguide structures. We propose a secondary melting dehydration technique that prepares high-quality Er3+-Yb3+ co-doped phosphate glass with low absorption loss. Additionally, we propose a femtosecond laser direct-writing technique that allows controlling the cross section, size, and mode field of waveguides written in glass with high accuracy, leveraging submicron-resolution multi-scan direct-writing optical waveguide technology, which is beneficial for reducing insertion loss. As a proof of concept demonstration, we designed and fabricated two kinds of waveguides, namely, LP01- and LP11-mode waveguides in the Er3+-Yb3+ co-doped phosphate glass, enabling insertion loss as low as 0.9 dB for a waveguide length of 2 mm. Remarkably, we successfully achieved an optical amplification for both the waveguides with a net gain of >7 dB and a net-gain coefficient of >3.5 dB/mm, which is approximately one order of magnitude larger than that in the Er3+-Yb3+ co-doped phosphate glass fabricated by the traditional melt-quenching method. This will open new avenues toward the development of integrated photonic chips.

Precise determination of energy transfer upconversion coefficient for the erbium and ytterbium codoped laser crystals.

Energy transfer upconversion (ETU) coefficient plays a crucial role in investigating complex laser systems as it greatly influences both the laser output behavior and heat generation. For some quasi-three-energy-level lasers based on Er3+ doped, Ho3+ doped and codoped gain media, the available theoretical studies relied on some unreasonable approximations due to the lack of spectroscopic data, notably the ETU coefficient. We put forward what we believe is a novel approach to overcome the difficulties caused by wavelength jump occurred in aforementioned laser systems. Based on net gain cross-section analysis and rate equations modelling, the functional relationship between the ETU coefficient, the laser power and pump power at the jumping wavelength are established. ETU coefficients and their temperature dependences of Er,Yb:YAB crystals with different crystal doped concentrations are experimentally determined for the first time. The results reveal that the ETU process in Er,Yb:YAB laser system is 5∼35 times stronger than that in Er3+ and Yb3+ codoped phosphate glass. The determination of these spectroscopic data paves the way for precise modelling of laser system based on Er,Yb:YAB or similar gain media.

Luminous properties of highly moisture-resistant Dy3+-Tm3+-Eu3+ co-doped phosphate glasses for W-LED

In this study, the high-temperature melt quenching method was used to create Dy3+-Tm3+-Eu3+ co-doped P2O5–CaO–K2O–ZnO series glasses (abbreviated PCKZ glasses). The samples were then subjected to various analyses such as X-ray diffraction, thermo-temperature property analyses, chemical stability analysis, Raman spectroscopy analysis, absorption spectroscopy, photoluminescence spectroscopy, fluorescence decay lifetime and CIE chromaticity coordinates to determine the structure and luminous properties of the glass. The sample’s density was determined, and the molar volume was calculated. The results reveal that the PCKZ series glasses prepared in this study are structurally stable and resistant to moisture. Following the addition of Eu3+ to the glass, the emission spectra revealed red emission from Eu3+ at 613 nm. The emission bands of Dy3+ and Tm3+ were enhanced as the concentration of Eu3+ increased, indicating an energy transfer between Eu3+ and Dy3+-Tm3+. The energy was fitted using the Inokuti-Hirayama (I–H) model resulting in energy transfer in dipole-dipole mode. Notably, the glass prepared in this study shows good moisture resistance and chemical stability, as well as emitting bright warm white light when exposed to 350 nm UV light excitation. Under UV simulation at 350 nm, the glass with the composition 50P2O5– 12CaO– 5K2O– 33ZnO-0.5Dy2O3-0.6Tm2O3-0.09Eu2O3 produces white light with a white colour temperature of 4954 K, colour coordinates of (0.3498, 0.3744), a long fluorescence lifetime of 0.498 ms, the quantum yield is 6.86 %, and it has good thermal stability. Therefore, it is considered that PCKZ: DTE (1, 2, 3) series glasses can be used in high humidity-resistant W-LEDs.

Broadband 1.0 µm emission in Nd3+/Yb3+ co-doped phosphate glasses and fibers for photonic applications.

In this work, the spectroscopic properties of 1.0 µm emission in Nd3+/Yb3+ co-doped phosphate glasses were systematically investigated under 808 nm excitation. Notably, broadband 1.0 µm emission with a full width at half maximum (FWHM) of 96 nm was obtained in the phosphate glass doped with 2 mol.% Nd2O3 and 1 mol.% Yb2O3. In addition, the energy transfer microscopic parameter and transfer efficiency were analyzed. What is more, multimaterial fibers with Nd3+/Yb3+ co-doped phosphate glass core and silicate cladding were successfully drawn by using the molten core method. An intense 1.0 µm amplified spontaneous emission (ASE) can be realized in a 3 cm long multimaterial fiber. More importantly, the FWHM of the ASE can reach as large as 60 nm when excited at 976 nm. These results demonstrate that the Nd3+/Yb3+ co-doped phosphate glasses and fibers are promising gain materials for amplifier and laser applications in photonics.

Extending the Palette of Luminescent Primary Thermometers: Yb3+/Pr3+ Co-Doped Fluoride Phosphate Glasses.

The unique tunable properties of glasses make them versatile materials for developing numerous state-of-the-art optical technologies. To design new optical glasses with tailored properties, an extensive understanding of the intricate correlation between their chemical composition and physical properties is mandatory. By harnessing this knowledge, the full potential of vitreous matrices can be unlocked, driving advancements in the field of optical sensors. We herein demonstrate the feasibility of using fluoride phosphate glasses co-doped with trivalent praseodymium (Pr3+) and ytterbium (Yb3+) ions for temperature sensing over a broad range of temperatures. These glasses possess high chemical and thermal stability, working as luminescent primary thermometers that rely on the thermally coupled levels of Pr3+ that eliminate the need for recurring calibration procedures. The prepared glasses exhibit a relative thermal sensitivity and uncertainty at a temperature of 1.0% K-1 and 0.5 K, respectively, making them highly competitive with the existing luminescent thermometers. Our findings highlight that Pr3+-containing materials are promising for developing cost-effective and accurate temperature probes, taking advantage of the unique versatility of these vitreous matrices to design the next generation of photonic technologies.

An Integrated Pump-Controlled Variable Coupler Fabricated by Ultrafast Laser Writing.

The design and fabrication of a integrated symmetric directional coupler dependent o the pumping power and operating at a 1534 nm wavelength is reported. The twin-core waveguide was inscribed into Er3+/Yb3+ co-doped phosphate glass by a femtosecond laser direct writing technique. By optical pumping, the coupling ratio can be modulated due to the changes induced in the refractive index of the material. The experimental results demonstrated that the coupling ratio can be tuned continuously from 100/0 to 50/50 by increasing the pump's power from 0 to 350 mW. The developed twin-core coupler has promising applications for on-chip all-optical signal processing and communication systems.

Spectroscopic investigation of neodymium and copper co-doped phosphate glass incorporating plasmonic nanoparticles

Spectroscopic investigation of neodymium and copper co-doped phosphate glass incorporating plasmonic nanoparticles

Yb3+ NIR emission enhancement in dichroic Cu-containing glass for solar spectral conversion

Ytterbium and copper co-doped phosphate glass containing plasmonic Cu particles showing dichroism was synthesized and the impact on Yb3+ near-infrared (NIR) emission evaluated. While the co-doped precursor glass exhibited ultraviolet to NIR luminescence down-shifting owing to copper(I), the dichroic glass displayed an enhanced NIR emission which is reported herein for the first time. It was found most favorable for Cu+ excitation around 360 nm. Scattering by Cu particles is suggested to produce the emission boost attractive for solar cell applications.

Enhanced NIR emission from Nd3+ ions in plasmonic & dichroic Cu nanocomposite glass

The optical properties of neodymium and copper co-doped phosphate glass were examined focusing on the impact of Cu nanoparticles (NPs) with distinct plasmonic properties on the Nd3+ near-infrared (NIR) emission. The glasses were synthesized with either merely plasmonic or plasmonic & dichroic (transmitting blue, scattering red) character. While the merely plasmonic glass exhibited Nd3+ photoluminescence (PL) quenching consistently, the dichroic glass showed an enhanced NIR emission for excitation at 747 and 803 nm. The Nd3+ 4F3/2 emitting state decay times were however similar to the melt-quenched precursor. Scattering effects from Cu NPs are suggested to produce the PL boost.

Breadboard of Microchip Laser and Avalanche Photodiode in Geiger and Linear Mode for LiDAR Applications

This paper reports the implementation of two critical technologies used in light detection and ranging for space applications: (1) a microchip Q-switched laser breadboard; (2) a breadboard of an indium gallium arsenide avalanche photodiode working at 292 K with high reverse polarization voltages. Microchip Q-switched lasers are small solid-state back-pumped lasers that can generate high-energy short pulses. The implemented breadboard used an erbium and ytterbium co-doped phosphate glass, a Co:Spinel crystal with 98% initial transparency, and an output coupler with 98% reflectivity. For the sensor test, a system for simultaneous operation in vacuum and a wide range of temperatures was developed. Avalanche photodiodes are reverse-polarized photodiodes with high internal gain due to their multiple layer composition, capable of building up high values of photocurrent from small optical signals by exploiting the avalanche breakdown effects. The test avalanche photodetector was assembled to be operated in two modes: linear and Geiger mode. The produced photocurrent was measured by using: (1) a passive quenching circuit; (2) a transimpedance amplifier circuit. These two technologies are important for mobile light detection and ranging applications due to their low mass and high efficiencies. The paper describes the breadboard’s implementation methods and sensor characterization at low and room temperatures with high bias voltages (beyond breakdown voltage).

White and tunable light emission of Ho3+ and Pr3+ ions co-doped phosphate glasses

The Ho3+ and Pr3+ ions co-doped phosphate glasses were prepared by melt quenching procedure with the various composition of (70-x-y)P2O5 + 20SiO2 + 10CaO + xHo2O3 + yPr2O3 (x = 0.4, 0.6, 0.8, 1.0 mol%, y = 0.6, 0.8, 1.0 mol%). The structural investigation (based on X-ray diffraction analysis) confirmed amorphous character of these glass materials. The optical properties were studied. The glass samples have strong absorption at 360 nm, and the excitation light at 360 nm can excite Ho3+ and Pr3+ ions very well, causing them to produce synergistic luminescence. The glass sample 68.8P2O5 + 20SiO2 + 10CaO + 0.4Ho2O3 + 0.8Pr2O3 emits strong white light under 360 nm excitation. The chromaticity coordinate values are x = 0.3378, y = 0.3472 in white light region, and it has a moderate correlated color temperature (CCT) of 5277 K. Decay time data reveals that there is energy transfer from Pr3+ to Ho3+ ions. This glass will be a good material for white light and tunable light emitting.

Spectral properties of ultra-low thermal expansion Er3+/Yb3+ co-doped phosphate glasses

An Er3+/Yb3+ co-doped phosphate glass with an ultra-low thermal expansion coefficient (55 × 10−7 K−1) was developed. The EYAP5 glass (80Al(PO3)3–20AlF3-1.5Er2O3-7.5Yb2O3, mol%) exhibits excellent spectral properties, thermomechanical properties, and chemical durability. Compared with traditional high phosphorus-doped silica glasses, EYAP5 glass achieves a higher Er3+/Yb3+ doping concentration and energy transfer efficiency from Yb3+ to Er3+ ions. Meanwhile, the absorption spectra, emission spectra, and fluorescence decay were systematically measured and compared in the temperature range of 300–480 K. Unlike the cases at 915 and 974 nm, the absorption cross section at 940 nm (∼0.21 pm2) has the highest temperature stability, which facilitates the stable operation of the 1.5 μm high-average-power laser. Furthermore, the temperature rises increase the energy transfer efficiency from Yb3+ to Er3+ ions, effectively suppressing the amplified spontaneous emission (ASE) at ∼1 μm.

Investigation of structural and optical properties: Tm2O3/Dy2O3 codoping in P2O5-MgO-NaF-CaF2 glass

Rare earth-doped glass is regarded as an excellent luminescent material and has been widely used in solid-state lighting. Here, the Tm3+/Dy3+ co-doped phosphate glasses revealed an increasing trend in density as the raising of Tm3+ contents, and the Urbach energies were 0.242∼0.374 eV based on transmission spectra. Under the 362 nm excitation, the white light with the chromaticity coordinates that were close to the value of standard white light was produced. The electric dipole-dipole interaction plays a major role in the energy transfer process from Tm3+ to Dy3+, and the glass exhibited a very high energy transfer efficiency of 64.44% according to the fluorescence spectra. Furthermore, the luminescent intensity of Tm3+/Dy3+ co-doped glasses at 150°C can still keep approximately 85.4% of its initial intensity and the glasses displayed excellent moisture-resistance (99.2%). Overall, the prepared Tm3+/Dy3+ co-doped glass exhibited potential applications in the field of W-LED and display devices.

White luminescence and energy transfer studies in Tb3+-Eu3+ co-doped phosphate glasses

Europium and Terbium co-doped phosphate glasses with a chemical composition of 80NaH2PO4–18Na2CO3–2Al2O3, which have been named PNA, were well produced with melt-quenching technique. We studied the structural and optical properties of the material. According to the XRD pattern, all the samples have an amorphous structure. After adding Tb3+, it was revealed that the photoluminescence (PL) intensity of the 5D0 →7F2 transition increased. It was observed that the Tb3+ ion functions as a sensitizer for the Eu3+ ion, and significantly enhances the spectroscopic features of Eu-doped PNA. We demonstrated the possibility of excitation transfer from Tb3+ to Eu3+. The radiative lifetime (τR) calculated from Judd-Ofelt (J-O) theory, and the, empirically discovered, measured lifetimes (τmes) were compared for Eu-doped PNA and (Eu; Tb) co-doped PNA. The results reveal that the quantum efficiency (η) was found to increase after adding Tb3+ from 87 to 94% for the 5D0 →7F2 transition. The energy transfer was identified and explained both experimentally using the excitation and emission spectra and theoretically using the J-O theory. The results of the CIE chromaticity coordinates of (Eu, Tb) co-doped PNA were found in the white region, which suggests a significant promise in field emission displays.

Structural and photoluminescence properties of Tm3+-Dy3+-codoped phosphate glasses

Luminescent glass has drawn widespread interest due to its exceptional properties and has been widely used in solid-state-lighting fields. Herein, a series of Q0, Q1 and Q2 group-containing Dy3+/Tm3+-codoped phosphate glasses with monotonically increasing density and glass stability were prepared. The glasses that emerged from this work displayed eight distinct absorption peaks in their absorption spectra, and the energy transfer from Dy3+ to Tm3+ manifested with the increase of Tm3+ contents under the excitation of 351 nm light. The temperature-dependent emission spectra demonstrated that the glass was thermally stable, and the fluorescence curves demonstrated that the energy transfer mechanism was the electric dipole-dipole interaction. Tuning the sensitizer and activator contents, white-light emission with suitable chromaticity coordinates and CCTs can be obtained. The findings indicated the potential prospects of this glass in lighting applications.

Analysis of down conversion and back-transfer processes in Pr3+-Yb3+ co-doped phosphate glasses

The visible to near-infrared spectral modification in Pr3+ and Yb3+ co-doped phosphate glasses were verified through the energy transfer from Pr3+ to Yb3+ ions. A series of 0.1Pr3+-xYb3+(x = 0.5, 1, 1.2 mol%) co-doped phosphate glasses were prepared by the melt quenching method. The absorption, excitation and emission spectra and fluorescence decays were measured and analyzed. The emission in the visible region and the luminescence decay times of the Pr3+ confirmed the coexistence of the down-conversion processes from Pr3+ to Yb3+ due to the mechanism: Pr3+(1D2) + Yb3+(2F7/2) → Pr3+(3F3) + Yb3+(2F5/2) and the cross relaxation processes between Pr3+ ions. The down conversion produces an important population of Yb3+ ions and consequently an intense emission at 975 nm. However, when the concentration of Yb3+ is larger than 0.5 mol% the emission from the Yb3+ start to decrease. In order to analyze all the transfer processes is proposed a generalized energy transfer model. Therefore, in basis to this model the luminescence decay curves of Yb3+ ions confirm an important back-transfer mechanism from these excited ions to the Pr3+ ions. This process limits the emission intensity of Yb3+ ions in the near-infrared region obtained by down-conversion under direct excitation of Pr3+ ions.