Μm Luminescence Research Articles

Broadband 1.45–2.1 μm luminescence in Er3+/Tm3+/Yb3+ tri-doped bismuth-germanate glasses

Optical properties of novel Er3+-doped, Er3+/Yb3+ and Er3+/Tm3+ co-doped and Er3+/Tm3+/Yb3+ tri-doped bismuth-germanate glasses were fabricated. Thermal characterization by differential scanning calorimetry showed the suitability of the glass for fiber drawing. Tri-doped sample presented a broadband luminescence spectrum ranging from 1450 to 2100 nm when it was excited by 980 and 1480 nm laser diodes. Energy transfer mechanisms from the donor (Yb3+, Er3+) to acceptor (Er3+, Tm3+) ions were found out to be the cause of the intense luminescence with broad bandwidth which can be tailored through doping content and concentration. It was observed that the Tm3+ addition helps broadening the luminescence spectrum, while the Yb3+ incorporation enhances the emission intensity. This study provides insightful contributions to the possibility of signal amplification in L + U-bands and beyond, up to 2100 nm.

2.7μm luminescence and structural properties of Er3+-doped fluorotellurate glass

In this paper, the thermal properties and internal structures of fluorotellurate glasses with different concentrations of TeO2 were studied. Glass samples with a concentration of 30mol% TeO2 were doped with different concentrations of Er3+ (1,2, 3,3.5,4,4.5,5mol%) and their luminescence characteristics were analyzed. The fluorotellurate glass possess high infrared transmittance (93 %), thermal stability (ΔT>110 °C), and low phonon energy (821 cm−1). Er3+ doped fluorotellurate glass exhibits high fluorescence lifetime of 4I11/2 level (1.59 ms), large emission cross-section (5.98 × 10−21cm2), and achieves a quantum efficiency of up to 30 %. These experimental findings suggest promising prospects for the utilization of Er3+ doped fluorotellurate glass in 2.7 μm laser applications.

Broadband ∼2 μm luminescence properties and energy transfer in Tm3+/Ho3+ co-doped TeO2–Al2O3–BaF2 glass

Tm3+/Ho3+ co-doped tellurite aluminate glasses were prepared using the melt-quenching technique. Under 808 nm laser diode (LD) excitation, these glasses exhibit intense 2 μm band luminescence, with a full width at half-maximum (FWHM) of 144 nm. The energy transfer mechanism between Tm3+ and Ho3+ was explored to investigate the luminescence behavior further. Furthermore, the forward energy transfer coefficient (Tm3+→Ho3+) is greater than the backward energy transfer coefficient (Ho3+→Tm3+), indicating that Tm3+ can effectively sensitize Ho3+. As mentioned above, Tm3+/Ho3+ co-doped tellurite aluminate glass is a competitive material in the laser field.

Broadband 2.85 μm Luminescence Properties of Er3+/Dy3+ Co-Doped Fluorotellurite Glass

TeO2-BaF2-Er2O3-Dy2O3 laser glasses were prepared using the melt-quenching method. The bound water that can capture the excited state energy was reduced by physical and chemical methods. We did not observe a significant Er3+ emission peak at 2.7 μm in fluorescence spectra, which may be due to the efficient energy transfer process (ET2). Meanwhile, we found a broadband gain span of approximately 400 nm in fluorescence spectra at the 2.85 μm band, attributed to the ‘vector summation’ of the energy level radiation transition and the change of the glass network. Subsequently, we explored the structural properties of the glass. The results indicated that the Gaussian peak located at 250 cm−1 drifts toward 370 cm−1, which may be caused by the fracture or recombination of Te-O-Te and a decrease in the bridge oxygen content with the increasing concentration of Er2O3. The topology cage structure around the luminescence center of rare earth ions is changed and the stability of the optically active center is enhanced, finally contributing to the enhancement of luminescence. Meanwhile, the maximum σemi and gain coefficient of Dy3+ reach up to 7.22 × 10−21 cm2 and 7.37 cm−1, respectively. The comprehensive results show that the fluorotellurite glass designed in this study is expected to be a gain medium for mid-infrared lasers in remote sensing monitoring, military, and other fields.

The deactivation effects of Nd3+ ion for 2.85 μm laser in Ho3+/Nd3+ co-doped fluorotellurite glass

The 2.85 μm band has garnered significant attention for its wide range of applications in the mid-infrared region, and Ho3+ doped fluorotellurite fiber shows great promise as a gain medium for the 2.85 μm fiber laser. To achieve efficient population inversion for Ho3+ ions at 2.85 μm, Ho3+/Nd3+ co-doped fluorotellurite glasses with low hydroxyl were synthesized. The deactivation effect of Nd3+ ions to Ho3+: 5I7 levels was investigated through emission spectra and lifetime decay curves under 890 nm excitation. The results show that Nd3+ ions can effectively quench the Ho3+: 2.05 μm emission and help the Ho3+: 5I6 → 5I7 transition to overcome the bottleneck of particle population inversion. Ultimately, the particle population inversion corresponding to 2.85 μm luminescence was realized in the Ho3+/Nd3+ co-doped fluorotellurite glass, and indicates that a maximum of 1.64 W laser at 2.85 μm with a slope efficiency of 8.72 % can be realized under 890 nm pump by numerical simulations.

Influence of Eu3+ ions on 1.5 µm luminescence of Er3+ in TeO2–ZnO–Bi2O3 glasses

TeO2–ZnO–Bi2O3 glasses doped with Eu3+ and Er3+ ions were prepared and investigated for their physical, optical, and luminescent properties. The optical band gap is calculated for the indirect transition and is within the 3.04–3.10 eV range. The Urbach energy varies from 0.135 to 0.098 eV with the increase in Eu3+ compound content. Bi2Te2O8 and ZnTeO3 complex oxide phases are generated in the mixture as intermediate compounds in the course of charge thermal processing. The additional doping of TeO2–ZnO–Bi2O3:Er3+ glass samples with Eu3+ ions is shown to lead to the appearance of cross-relaxation channels of the Er3+ ion states and decreases the population of the 4I13/2 state of the Er3+ ions. Simultaneously, the excited 4I11/2 state of the Er3+ ions is also subjected to strong cross-relaxation decay. The Eu3+ ions are shown to decrease the 4I13/2 level population of Er3+ ions, which may facilitate the attainment of population inversion if the 4I13/2 level is at the lower level of the laser transition.

Effective 3.9 μm emission in fluorotellurate glass with Ho3+: Highly doping

The ∼3.9 μm mid-infrared (MIR) laser based on high concentration Ho3+ doped fluoride glass possesses unique advantages, but its low thermal stability does not meet the requirements of the MIR laser technology for optoelectronic device materials. In this paper, fluorotellurate glass with TeO2 and high doping concentration of Ho3+ was prepared. The excellent thermodynamic properties (ΔT = 108 °C) and low phonon energy (799 cm−1) render the matrix a promising candidate for the development of laser gain medium doped with Ho3+: ∼3.9 μm. The calculated theoretical parameters and the measured spectral information confirm that the scheme of ∼3.9 μm luminescence by high doping of Ho3+ in the fluorotellurate glass matrix is reasonable and effective.

Realization of broadband ∼1.8 μm luminescence by level population inversion in Tm3+ doped tellurite glass for laser applications

This study aims to investigate the characteristics of Tm3+ doped TeO2–B2O3–Al2O3Na2O glass. The structures that exist in host glass were obtained from the Raman spectrum. Due to the introduction of sodium and aluminum, the TeOTe bond is broken, and the amount of bridge oxygen is reduced, causing the transformation of [TeO4] structural units to [TeO3+1] and [TeO3] structural units. The spectrum characteristics of Tm3+ in the samples were predicted by theoretical calculations. Prepared Tm3+ doped glass has large Ω2 and small Ω6, which is connected to the ligand field's asymmetry and the stiffness of the network. Furthermore, under the excitation of 808 nm laser diode, broadband ∼1.8 μm fluorescence was observed and the effective fluorescent bandwidth Δλeff of 1830 nm emission in the glass is about 234 nm. For the sample with 0.5 mol% Tm2O3, the large values of emission cross-section product (9.08 × 10−21 cm2) and σemi × Δλeff product (21.25 × 10−26 cm3) indicate a good gain property as well as a good gain bandwidth. Eventually, the energy migration process and cross-relaxation process between thulium ions were analyzed. The micro-parameter of the CR process is 4.049 × 10−40 cm6/s. Hence, the results indicate that the prepared Tm3+ doped glass could be a potential candidate for ∼2 μm mid-infrared laser devices.

Investigation of broadband 1.8 μm luminescence in Tm3+ activated gallium tellurite glass with high quantum efficiency

Investigation of broadband 1.8 μm luminescence in Tm3+ activated gallium tellurite glass with high quantum efficiency

High-efficiency 3.5 [formula omitted] luminescence of heavily Er[formula omitted] doped multicomponent glasses

The ∼3.5μm mid-infrared laser based on a high concentration of Er3+-doped multicomponent glasses possesses unique advantages, but the existing traditional glass hosts, which are inherently flawed, lead to challenging research. In this paper, oxyhalide glasses with tellurite (TeO2-Na2O-ZnO as the main body) and chloride (ZnCl2 as the modifier) are obtained with a high doping concentration of Er3+. It is worth noting that the microstructure can be adjusted to obtain excellent luminescence properties, while ensuring the thermal properties of the matrix. Both the actual performance test and theoretical calculation show that the scheme of realizing ∼3.5μm luminescence by high Er3+ doping in the present oxyhalide glass matrix is reasonable and effective, which provides a new choice for Er3+-doped ∼3.5μm laser gain medium in the future.

Enhanced 3 μm luminescence in Ho3+/Yb3+ co-doped bismuth-tellurite glass by controlled structure network topology

Ho3+/Yb3+ co-doped bismuth-tellurite glasses (TeO2-Bi2O3-ZnO) have been investigated systematically according to the Raman, absorption, and mid-infrared luminescence spectra, contraposing 3 μm band. The evolution of luminescence and structure has been explored by modifying network topology based on the substitution of TeO2 with WO3 when the optimal concentration ratio of Ho3+/Yb3+ was determined in TBZ glass. The results show that WO3 entered the glass structure network as [WO4] and [WO6] units, contributing to the content of bridging oxygen and network connectivity increased, which can be enhanced effectively the luminescence properties. The gain cross-section is 1.51 × 10−20 cm2 (2884 nm) increasing by 11.85% compared with the glass without glass network modifiers. Moreover, the energy transfer micro-parameters have been calculated based on a spectral overlap method. The CD-A was augmented from 0.36 to 1.11 × 10−40 cm6/s. As mentioned above, the bismuth-tellurite glasses have the potential as the gain materials for mid-infrared fiber lasers.

Excellent luminescence performance of Ho3+ ions based on a new system of oxyhalide glass

Ho3+ ion has attracted attention owing to its rich energy level structures and ability to emit emissions covering from visible to mid-infrared region. However, finding a suitable host of solid luminescence matrix material for its luminescence is a huge challenge at present. In this paper, a new system of oxyhalide glass based on tellurite-germanate and modified with MgCl2 is investigated. It is worth mentioning that through the mixed structural design, the thermal properties of the matrix are further optimized, and the symmetries of the coordination structure near Ho3+ are broken, thus making a great contribution to improving Ho3+ 2–3 μm luminescence, with more than 4-fold increase in fluorescence intensities, and long fluorescence lifetime of 1.24 ms for Ho3+: 5I7 level. The combined experimental characterizations and theoretical calculations confirm that oxyhalide glass is a very advantageous matrix material, which provides more possibilities for the application of Ho3+ in MIR lasers.

Enhanced structural and spectroscopic properties of Er3+-doped TeO2-Ta2O5-ZnO glasses for 2.7 μm fiber lasers

Tellurite-based glass composed of TeO2-Ta2O5-ZnO (labeled as TTZ) is explored as the host material for a potential 2.7 μm fiber laser. It is found that the glass-forming region, structural and physical properties of TTZ glass undergo considerable changes when platinum crucible are adopted to prepare glass instead of alumina one. Especially, the Er3+-doped TTZ glass that melted in platinum crucible exhibits relatively larger absorption and emission cross-sections at 2.7 μm than that of alumina one. Further studies show that an enhanced 2.7 μm luminescence can be achieved from the heavily Er3+-doped TTZ glass, the absorption and emission cross-sections, figure of merit and maximum gain coefficient of Er3+-doped TTZ-Pt glasses at 2.7 μm are calculated to be 0.91 × 10−20 and 1.01 × 10−20 cm2, 3.18 × 10−24 cm2·s and 2.25 cm−1, respectively, indicating that the Er3+-doped TTZ glass may be a promising candidate host for mid-infrared fiber lasers.

High quantum efficiency of 1.8 μm luminescence in Tm3+ fluoride tellurite glass

In this paper, Tm3+ doped fluorotellurite glasses are synthesized by melt-quenching technique. The thermal and spectral properties of the glasses are characterized. The effect of the 1.8 μm emission properties for different Tm3+ concentrations are investigated. ΔT (153 ℃) of the glass indicates it has good thermal stability. Spectroscopic parameters of Tm3+ such as radiative transition probability, branching ratio, spectroscopic quality factor, integrated emission cross section and radiative lifetime are calculated on the basis of Judd-Ofelt analysis. The maximum half-height width corresponding to 1.8 µm broadens as Tm3+ increases and reaches a maximum of 216 nm, as well as the longer lifetime (5.68 ms). For 1.8 µm (3F4 → 3H6) emission band, the calculated Tm3+ doped fluorotellurite glass has a high quantum efficiency of 75.93%. Furthermore, the theoretical analysis of the energy transfer mechanism between Tm3+ ions were represented. Therefore, these results demonstrate that prepared Tm3+ doped fluorotellurite glass is an ideal laser material for 1.8 µm band solid-state laser applications.

Enhanced 2-3 Μm Luminescence in Ho3+/Yb3+ Co-Doped Bismuth-Tellurite Glass by Controlled Network Structure Modification

Enhanced 2-3 Μm Luminescence in Ho3+/Yb3+ Co-Doped Bismuth-Tellurite Glass by Controlled Network Structure Modification

High-Efficiency 3.5 Μm Luminescence of Er3+ Based on High-Concentration Doping in Multicomponent Glasses

High-Efficiency 3.5 Μm Luminescence of Er3+ Based on High-Concentration Doping in Multicomponent Glasses

Luminescence Characteristics of Ho3+/Tm3+Co-Doped Bi2O3–GeO2–Ga2O3–Na2O Laser Glasses

The Ho3+/Tm3+co-doped 35Bi2O3–40GeO2–15Ga2O3–10Na2O laser glass was synthesized by high temperature melting method. The 2.0μm luminescence characteristics of system glass under central wavelength of 808 nm pumping light excitation were researched, and the fluorescence intensity changing with the doping concentration of Ho3+was analyzed at Tm3+content of 3-mol%. The results indicate that the 2.0μm luminescence of Ho3+is remarkably changed due to the doping ratio of Ho3+/Tm3+. The fluorescence intensity was achieved for the lase glass in the system when the sensitization ratio of Ho3+/Tm3+is 0.5:3 mol%. Its maximum emission cross-section at 2.05μm reaches 7.32 × 10−21cm2, while the gain characteristic ofσemi×τradvalue can get 35.50 × 10−21cm2· ms, and the gain coefficient achieves 2.30 cm−1. Furthermore, the Gaussian decomposition method was employed to fit the spectrum of host glass, maximum phonon energy is 812 cm−1. It indicates that the host gets small phonon energy which is benefit to the 2.0μm laser emission. In summary, results purport that Ho3+/Tm3+co-doped bismuth-germanate system laser glass is a good ~2μm laser gain glass material with good gain characteristics.

Effect of intrinsic point defects on the electronic and optical properties of Ho:BYF crystal

First-principles methods have been applied to explore the effect of intrinsic point defects on the electronic and optical properties of Ho:BYF crystal. Among the intrinsic point defects in Ho:BYF crystal, fluorine vacancies (VF1, VF2, VF3) and interstitial defects (BaIn, YIn, FIn) have lower formation energy and more stable structure. The calculated electronic properties manifest that the new defect states appear and the overall electronic density of states shifts to the lower energy region. The principal absorption at around 0.613 eV (2 μm) of fluorine vacancies (VF1) occurs in the near-infrared range owing to the electronic transitions from the occupied f-orbitals of the Ho atoms to empty f-orbitals of neighboring Ho atoms. Therefore, there may be a 2 μm luminescence in the Ho:BYF crystal because of the interaction of doping Ho atom and fluorine vacancies defects (VF1).

Improved 2.0 μm luminescence by doping Ce3+ ions in Yb3+, Ho3+:YAG transparent ceramics

A series of Yb3+, Ho3+, Ce3+:YAG ceramics have been sintered at 1780 °C by high temperature solid state reaction under oxygen atmosphere. The absorption spectra, fluorescence spectra and fluorescence decay curve were discussed. The Judd-Ofelt (J-O) theory was applied to obtain the values of Ω2 = 13.95 × 10−20 cm2, Ω4 = 3.94 × 10−20 cm2 and Ω6 = 0.87 × 10−20 cm2, respectively. After doping the Ce3+ ions, the σem of Yb3+, Ho3+, Ce3+:YAG ceramic at 2094 nm increased from 5.67 × 10−20 cm2 to 7.26 × 10−20 cm2. These results demonstrate that Yb3+, Ho3+, Ce3+:YAG ceramic could be promising for 2 μm region.

1.53 μm luminescent properties and energy transfer processes of Er3+/Yb3+ co-doped bismuth germanate glass laser material

In this work, Er3+/Yb3+ co-doped 40Bi2O3-30GeO2-15Ga2O3-15Na2O glass was papered by melt-quenching method. The thermal properties and spectroscopic were studied. The glass has good thermal stability and the maximum phonon energy is 750 cm−1, which is benefited for 1.53 μm emission. According to the J-O theory and absorption spectra, the J-O intensity parameters were calculated, the spectral quality factor χ = Ω4/Ω6 of BGGN4 glass is 2.236. Under 980 nm excitation, the 1.53 μm luminescence characteristics of these glasses were studied. When the Er3+/Yb3+ ions doping concentration ratio (mol%) reaches 0.5:1.0, the maximum fluorescence intensity can be obtained, and the maximum emission cross section is 6.4 × 10−21cm2. The maximum stimulated gain coefficient in the 1.53 μm band is 4.6 cm−1. Finally, the up-conversion emission and energy transition mechanism of Er3+/Yb3+ co-doped BGGN glass were studied. The results indicate the prepared Er3+/Yb3+ co-doped bismuth germanate glass have good gain performance and is an ideal 1.53 μm laser gain material.