Energy Transfer Microparameters Research Articles

Periodic lattice microscopic rate equation model for upconversion dynamics and determination of energy transfer microparameters

Periodic lattice microscopic rate equation model for upconversion dynamics and determination of energy transfer microparameters

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.

Spectroscopic properties of gallium-rich germano-gallate glasses doped with Tm3+

A series of thulium-doped gallium-rich germano-gallate glasses are fabricated and thoroughly investigated. Their synthesis under an atmosphere-controlled glove box allows for a low hydroxyl concentration estimated at 14 wt ppm. From X-Ray diffraction spectroscopy and differential scanning calorimetry, the vitreous state of such gallium-rich BGG composition is confirmed. A structural analysis performed via Raman spectroscopy supports a three-dimensional interconnected glass network of gallium and germanium tetrahedra stabilized by Ba2+ ions as a charge compensator. From steady-state and time-resolved spectroscopies, Judd-Ofelt analysis is applied to determine the radiative transition rates, both absorption and emission cross-sections along with the resonant energy transfer microparameters. Through laser excitation at 808 nm, the intense 1.8 μm trivalent thulium emission is observed, while no concentration quenching is detected. Hence, the present work demonstrates gallium rich-BGG glasses doped with Tm3+ are suitable systems for IR photonic applications, notably for the development of high-power IR lasers.

Upconversion and near infrared emission in Yb–Tm mediated by ZnTe crystals in oxide glasses

This work presents a detailed investigation of the blue and near infrared (NIR) emission of Tm3+ and Yb3+ ions in ZnTe doped oxide glasses. Absorption, luminescence and lifetime measurements were performed in order to optimize the luminescent properties of Yb3+ and Tm3+. The influence of ZnTe and Yb3+ concentration on the enhancement and quenching of the emissions at 470 nm and 980 nm were determined. It was observed that the Yb3+ luminescence increases by a factor of 10, while the Tm3+ blue emission at 470 nm is quenched for both the presence of Yb3+ and ZnTe. The enhancement in the Yb3+ emission is attributed to the presence of ZnTe. Moreover, it is demonstrated that the glass can be pumped with additional wavelengths (325 nm and 532 nm) due to the absorption from the ZnTe semiconductor, allowing alternative pumping schemes. Calculations of the energy transfer microparameters from Yb3+-Yb3+ and Yb3+-Tm3+ were also performed, evaluating the influence of ZnTe in the process.

Efficient Yb3+ sensitized Er3+ emission of Bi2ZnOB2O6:Yb3+/Er3+ single crystal

Bi2ZnOB2O6 single crystals doped with Er3+and Yb3+ ions were grown by means of the Kyropoulos method. Bi2ZnOB2O6:Yb3+/Er3+ crystals were characterized by high values of nonlinear optical coefficients as well as efficient luminesce of Er3+ ions. The structure, vibrational and luminescent properties of Bi2ZnOB2O6:Yb3+/Er3+ crystals were investigated for the first time. The Raman investigation showed the low phonon energy of Bi2ZnOB2O6 host matrix associated to the vibrations of BO3, BO4, ZnO4 and BiO6 molecular groups, which allow effective phonon assisted energy transfer between Yb3+ and Er3+ ions. The 1532 nm emission of Bi2ZnOB2O6:Yb3+/Er3+ crystals, associated with the 4I13/2 → 4I15/2 transition of Er3+ ions, was excited at 380 (by Bi3+ ions), 488 (by Er3+ ions) and 980 nm (by Yb3+ ions) and efficient Yb3+ sensitization of Er3+ emission was observed. Moreover, the longest decay lifetime equal to 1.36 ms of Er3+ emission at 1532 nm was observed for Bi2ZnOB2O6:Yb3+/Er3+ crystals under 980 nm excitation. Additionally, using the Inokuti - Hirayama model, the kinetics of the fluorescence intensity was analyzed, besides, the energy transfer micro-parameter CDA and the energy transfer rate parameter WDA were determined for Bi2ZnOB2O6:Yb3+/Er3+ crystals. The results indicate a great potential of new multifunctional Bi2ZnOB2O6:Yb3+/Er3+ crystals for application in the integrated new-generation laser devices.

New NIR emission from Sm3+ in Yb3+-Sm3+ co-doped tellurite glass

Yb3+, Sm3+ and Yb3+-Sm3+ doped tellurium oxide glasses were prepared. Their spectroscopic properties in the near-infrared region were studied. In the singly doped Sm3+ glass, excited by 403 nm, emission transitions occurred from the usual level 4G5/2 leading to strong fluorescence mainly in the visible range. In the co-doped Yb3+-Sm3+ glass Yb3+ donor ions were excited by 976 nm and transferred their energy by non-radiative processes to Sm3+ acceptor ions, promoting them to 6F11/2 and 6F9/2. Using an amplified spontaneous emission experiment, new emissions in Sm3+ from 6F11/2 and 6F9/2 were observed at 1080, 1240, 1435 and 1457 nm. These are the first reported emissions from these levels in Sm3+. The Yb3+ to Sm3+ energy transfer process was studied by measurement of the fluorescence decay curve of the Yb3+ donor. A diffusion model taking into account the migration of excitation amongst the Yb3+ donor ions was used to fit the decay curve and subsequently determine the donor-acceptor energy transfer microparameter CDA and the transfer parameter γ. The experimental values of these parameters were higher than those calculated by Dexter's model for resonant non-radiative transfer between donor and acceptor ions. These results demonstrate the importance of the non-resonant phonon-assisted Yb3+ to Sm3+ energy transfer processes in the tellurite glass. Energy transfer was efficient as evidenced by a large reduction in the Yb3+ lifetime in the Yb3+-Sm3+ glass compared to in the singly doped Yb3+ glass. The new emissions from Sm3+ were though of low fluorescent intensity. This was due to the high non-radiative decay rates of levels 6F11/2 and 6F9/2 by multi-phonon relaxation.

Cold white light emission in tellurite-zinc glasses doped with Er3+–Yb3+–Tm3+ under 980 nm

Tellurite-zinc glasses doped with Er3+, Yb3+ and Tm3+ were fabricated by conventional melt-quenching technique and characterised by absorption spectroscopy, refractive index, lifetime measurements, excitation, luminescence and up-conversion spectroscopy. Tunable blue to cold white light emission based on the colour mixing of red, green and blue light was obtained via up-conversion under 980 nm and by adjusting the laser excitation intensity. The balancing of the relative intensity of each colour is provided by the energy transfer process between the rare-earth ions. Moreover, luminescence spectroscopy was performed with a 405 nm laser to further understand the energy transfer mechanism that produce the white light. The Judd-Ofelt intensity parameters (Ω2, Ω4 and Ω6) were calculated for all samples and present the trend Ω2>Ω4>Ω6. The spectroscopic parameters were computed with the Judd-Ofelt theory as well as the energy transfer micro-parameters (critical radius of interaction and energy transfer coefficient). Such results shall be used to give a comprehensive explanation for the energy transfer process between these rare earth ions.

Enhanced broadband 3 μm emission in Yb3+/Dy3+:YAlO3 crystal under 979 nm excitation

Yb3+ ion was introduced as a sensitizer for commercial 980 nm pump source utilization in Yb3+/Dy3+ co-doped YAP crystal for the first time. An intense broadband 3 μm emission (Dy3+:6H13/2 → 6H15/2 transition) in Yb3+/Dy3+:YAP crystal was demonstrated. As compared with Dy3+ singly-doped YAP crystal under 802 nm OPO excitation, the larger emission cross-section (=4.25 × 10−21 cm2) and effective emission bandwidth (=316 nm) were obtained in Yb3+/Dy3+:YAP crystal under 979 nm OPO laser excitation, which make it favorable for tunable lasers. The energy transfer efficiency from Yb3+ to Dy3+ was obtained as high as 97.2%. The greatly reduced near-infrared emission of Yb3+:2F5/2 → 2F7/2 transition and largely shortened lifetime of Yb3+:2F5/2, also reveal the efficient energy transfer from Yb3+ to Dy3+. The energy transfer micro-parameters were calculated by spectral overlapping integral method, and the main energy transfer channel is determined. In addition, the energy dispersive X-ray spectroscopy, X-ray diffraction and Raman spectrum were measured in Yb3+/Dy3+:YAP crystal. Rietveld refinement was also employed to investigate the variation in lattice parameters in Yb3+/Dy3+:YAP crystal. It can be concluded that Yb3+/Dy3+:YAP is an excellent candidate for achieving mid-infrared laser.

Energy transfer and luminescent properties of Eu3+, Tb3+, Eu3+-Yb3+and Tb3+-Yb3+ doped α-NaYF4 nanophosphors prepared by coprecipitation route

Cubic α-NaYF4 nanometer-sized crystals doped with Eu3+, Tb3+, Yb3+-Eu3+ or Yb3+-Tb3+ were synthesized by an original coprecipitation route. The obtained nanoparticles exhibited primary particles showing cubic shape with sizes ranging between 35 and 65 nm. The singly- or co-doped nanophosphors exhibited strong red (Eu3+) or green (Tb3+) fluorescence upon ultraviolet (UV) or near infrared (NIR) excitation, which resulted respectively from down- or up-conversion processes occurring in their structure. Spectroscopic properties were investigated on the basis of emission spectra as well as luminescence decays. From the emission spectra of Eu3+ doped samples, the Ω2 and Ω4 Judd-Ofelt intensity parameters were calculated. The concentration quenching of the Eu3+ or Tb3+ ion emissions in singly-doped or Yb3+ co-doped α-NaYF4 were ascribed to resonant cross-relaxations. The main derived interaction between the active ions was evidenced as an electric dipole-dipole one through fitting the decays curves with the Inokuti-Hirayama model. The critical distances and energy transfer microparameters for the transfer processes were given showing very short range interaction. The dependence of integral up-conversion intensity on the NIR energy of the beam power was measured. The results indicated a two-photon process based on a cooperative energy transfer.

Ho3+ doped Na5Y9F32 single crystals doubly sensitized by Er3+ and Yb3+ for efficient 2.0 μm emission

The 2.0 μm spectral characteristics of the 980 nm LD pumped Er3+/Ho3+/Yb3+ tri-doped Na5Y9F32 single crystals grown by an improved Bridgman method were investigated with the help of their absorption spectra, emission spectra and decay curves. The introduction of Yb3+ and Er3+ greatly improves the 2.0 fluorescence intensity through joint energy transfer processes from Yb3+ to Er3+, and Er3+ to Ho3+. The doping concentrations of 0.5 mol% Er3+ and 1.0 mol% Yb3+ ions were optimized to obtain the maximum 2.0 μm fluorescence intensities for the fixed 0.8 mol% Ho3+/1 mol% Yb3+ and 0.8 mol% Ho3+/0.5 mol% Er3+ doped Na5Y9F32 single crystals. Besides, according to the absorption and fluorescence spectra of the crystals, the absorption and emission cross-sections were calculated, and excellent gain performance was also obtained. Meanwhile, the maximum 2.0 μm emission lifetime of Er3+/Ho3+/Yb3+ tri-doped Na5Y9F32 single crystal can reach ~21.82 ms. The energy transfer mechanisms among the three rare-earth ions were further investigated by calculating energy transfer micro-parameters (CDA) and efficiencies. The excellent properties in both intense emission at 2.0 μm and chemical stability obtained in the Er3+/Ho3+/Yb3+ tri-doped Na5Y9F32 single crystals make them promising candidate material for 2.0 μm laser.

Relaxation dynamics of excited states of Tm3+ ions in TeO2-ZnO-Na2O-Y2O3 glasses

Tellurite glasses with the composition of xTm2O3-(6−x)Y2O3-3Na2O-25ZnO-66TeO2 (where 0 ≤ x ≤ 6) were obtained by the melt-quenching technique. Absorption (300 K), excitation (300 K) and fluorescence spectra (300 K) as well as fluorescence decay curves of Tm3+-doped title glasses are presented and discussed in details. The Judd–Ofelt analysis based on the room temperature absorption spectrum was applied for determination of fundamental fluorescence properties such as radiative transition probabilities (AT), branching ratios (βR), radiative lifetimes (τR) of the emitting levels of the Tm3+ ion and stimulated emission cross-sections (σem). Fluorescence spectra were recorded and analysed in the visible and near-infrared spectral range. The emission and effective cross-section were calculated for the 3F4→3H6 transition, showing that the investigated glasses are promising laser host materials, operating at 1.8 μm. The observed concentration quenching and non-exponential decay curves from the 1G4 and 3H4 states indicate nonradiative energy transfer between Tm3+ ions. The analysis of non-exponential fluorescence decay curves from the 1G4 and 3H4 levels was carried out in framework of the Inokuti-Hirayama and Yokota-Tanimoto models and energy transfer microparameters were determined. The self-quenching model was proposed for describing relaxation of the first excited state of the Tm3+ ion.

Enhanced luminescence at 2.88 and 2.04 μm from Ho3+/Yb3+ codoped low phonon energy TeO2–TiO2–La2O3 glass

The high phonon energy and short infrared cut-off wavelength of conventional oxide glass (or crystal) hosts are the limitations to achieve mid-infrared (MIR, λ≥2.5μm) luminescence. In present study, the luminescence performance of low phonon and non-conventional TeO2-TiO2-La2O3-based glass (TTL) host doped with Ho3+ and Ho3+/Yb3+ has been investigated, for visible to MIR range. The MIR emission band with peak at 2.88μm (Ho3+:5I6→5I7) and NIR band at 2.04μm (Ho3+:5I7→5I8) has been realized from Ho3+ singly doped TTL glass due to low phonon energy and extended transmission window of the host. Intensity of MIR and NIR emission bands have enhanced significantly in Ho3+/Yb3+: TTL glass under Yb3+ excitation, signifying an efficient Yb3+→Ho3+ energy transfer. The Judd-Ofelt analysis, on Ho3+ absorption characteristics reveals relatively better radiative transition probability (34.4s−1) and branching ratio (10.5%), which is associated to Ho3+:5I6→5I7 transition. The effective bandwidth of 2.88μm emission band is 180nm, with stimulated emission cross-section is 4.26×10-21cm2 and its gain bandwidth has been evaluated as 7.67×10-26cm3. For 2.04μm (Ho3+:5I7→5I8) emission band, the effective bandwidth of 160.5nm and gain bandwidth of 7.26×10-26cm3 have been accomplished. The non-resonant Förster-Dexter method has been applied to Ho3+/Yb3+: TTL glass on emission (donor, Yb3+) and absorption (acceptor, Ho3+) cross sections. The evaluated donor-donor (CDD) and donor-acceptor (CDA) energy transfer micro-parameters are 1.02×10-38 and 5.88×10-41cm6/s respectively while, maximum energy transfer efficiency has been 80%. In concise, Ho3+/Yb3+ codoped TeO2–TiO2–La2O3 glass host has revealed its potential for MIR to NIR photonic applications.

Co-effects of Yb^3+ sensitization and Pr^3+ deactivation to enhance 27 μm mid-infrared emission of Er^3+ in CaLaGa_3O_7 crystal

Er3+/Yb3+/Pr3+: CaLaGa3O7 crystal was successfully grown by the Czochralski method. Detailed spectroscopic analyses of Er3+/Pr3+: CaLaGa3O7, Er3+/Yb3+: CaLaGa3O7 and Er3+/Yb3+/Pr3+: CaLaGa3O7 crystals were carried out. Compared with Er3+/Pr3+: CaLaGa3O7 and Er3+/Yb3+: CaLaGa3O7 crystals, Er3+/Yb3+/Pr3+: CaLaGa3O7 crystal not only shows a better absorption characteristic but also exhibits weaker up-conversion and near-infrared emissions, as well as superior mid-infrared emission. Furthermore, the self-termination effect for the 2.7 μm erbium laser is suppressed successfully since the fluorescence lifetime of the 4I13/2 lower level of Er3+ decreases markedly while that of the upper 4I11/2 level falls slightly in Er3+/Yb3+/Pr3+: CaLaGa3O7 crystal. Besides, the sensitization effect of Yb3+ and deactivation effect of Pr3+ ions as well as the energy transfer mechanism in Er3+/Yb3+/Pr3+: CaLaGa3O7 crystal were studied in this work. Moreover, energy transfer microparameters between Yb3+ and Er3+ were also calculated and analyzed based on Dexter's model. In conclusion, the introduction of Yb3+ and Pr3+ is favorable for achieving an enhanced 2.7 μm emission in Er3+/Yb3+/Pr3+: CaLaGa3O7 crystal which can act as a promising candidate for mid-infrared lasers.

Infrared fluorescence, energy transfer process and quantitative analysis of thulium-doped niobium silicate-germanate glass

Infrared fluorescence, energy transfer process, thermal stability and quantitative analysis of Tm3+ doped novel niobium silicate-germanate glasses have been investigated. The thermal stability changes indicate that the introduction of La2O3 to substitute for Nb2O5 can improve the anti-crystallization of present glass system. Intense 1.8μm fluorescence has been achieved and the value of emission cross section can reach as high as 12.2×10−21cm2. Besides, the microparameters of energy transfer were analyzed by the extended overlap integral method. Hence, the results indicate that the excellent spectroscopic characteristics of this kind of silicate-germanate glass together with the good thermal properties may become a promising matrix applied for 1.8μm band near-infrared laser.

Tm3+/Yb3+ co-doped tellurite glass with silver nanoparticles for 1.85 μm band laser material

Tm3+/Yb3+ co-doped tellurite glasses with different silver nanoparticles (Ag NPs) concentrations were prepared using the conventional melt-quenching technique and characterized by the UV/Vis/NIR absorption spectra, 1.85 μm band fluorescence emission spectra, transmission electron microscopy (TEM) images, differential scanning calorimeter (DSC) curves and X-ray diffraction (XRD) patterns to investigate the effects of Ag NPs on the 1.85 μm band spectroscopic properties of Tm3+ ions, thermal stability and structural nature of glass hosts. Under the excitation of 980 nm laser diode (LD), the 1.85 μm band fluorescence emission of Tm3+ ions enhances significantly in the presence of Ag NPs with average diameter of ∼8 nm and local surface Plasmon resonance (LSPR) band of ∼590 nm, which is mainly attributed to the increased local electric field induced by Ag NPs at the proximity of doped rare-earth ions on the basis of energy transfer from Yb3+ to Tm3+ ions. An improvement by about 110% of fluorescence intensity is observed in the Tm3+/Yb3+ co-doped tellurite glass containing 0.5 mol% amount of AgNO3 while the prepared glass samples possess good thermal stability and amorphous structural nature. Meanwhile, the Judd-Ofelt intensity parameters Ωt (t = 2,4,6), spontaneous radiative transition probabilities, fluorescence branching ratios and radiative lifetimes of relevant excited levels of Tm3+ ions were determined based on the Judd-Ofelt theory to reveal the enhanced effects of Ag NPs on the 1.85 μm band spectroscopic properties, and the energy transfer micro-parameters and phonon contribution ratios were calculated based on the non-resonant energy transfer theory to elucidate the energy transfer mechanism between Yb3+ and Tm3+ ions. The present results indicate that the prepared Tm3+/Yb3+ co-doped tellurite glass with an appropriate amount of Ag NPs is a promising lasing media applied for 1.85 μm band solid-state lasers and amplifiers.

Energy transfer and upconversion of Sm3+ ions in YAlO3

Sm3+ doped YAlO3 (YAP) single crystals were prepared by the micro-pulling down method. Emission spectra as well as luminescence decay curves for these crystals were recorded at temperatures ranging from 10 K to 300 K. Based on the low temperature spectra the energies of the Stark levels for several multiplets were determined. The fluorescence decay curves have been measured as a function of concentration and temperature and are found to exhibit single exponential nature at lowest concentration of 0.1 at.% but are strongly non-exponential at concentrations above 1 at.%. This concentration quenching of the Sm3+ ion emission was ascribed to resonant cross-relaxation. The non-exponential decay rates were successfully fitted to Inokuti-Hirayama model for s = 6 indicating that the nature of the energy transfer process among the Sm3+ ions is of electric dipole-dipole type. Cross-relaxation rates were experimentally determined as a function of activator concentration and used to evaluate and to model the decays. The critical distances and energy transfer microparameter for the transfer processes were given.After pulsed 925–975 nm infra-red excitation upconverted yellow-orange emission has been generated at room temperature in Sm3+:YAP crystals. Dynamics of the involved excited states have been analyzed and the responsible upconversion mechanism was proposed to be energy transfer.

The 1.85 μm spectroscopic properties of Er3+/Tm3+ co-doped tellurite glasses containing silver nanoparticles

The Er3+/Tm3+ co-doped tellurite glasses with and without silver nanoparticles (Ag NPs) have been synthesized by the conventional melt-quenching technique and characterized by the UV/Vis/NIR absorption spectra, 1.85 μm band fluorescence emission spectra, differential scanning calorimeter (DSC) curves, X-ray diffraction (XRD) curves and transmission electron microscopy (TEM) images to investigate the effects of Ag NPs on the 1.85 μm band spectroscopic properties of Tm3+ ions, thermal stability and structural nature of glass hosts. The TEM image reveals the presence of Ag NPs with average diameter of ∼14 nm in the prepared Er3+/Tm3+ co-doped tellurite glasses, and the presence of Ag NPs significantly enhance the 1.85 μm band fluorescence emission of Tm3+ ions under the excitation of 808 nm LD, which is mainly attributed to the intensified local electric field induced by Ag NPs scattered around the doped rare-earth ions, together with the energy transfer between Er3+ and Tm3+ ions. The energy transfer mechanisms between Er3+ and Tm3+ ions were further investigated by calculating energy transfer micro-parameters and phonon contribution ratios. Meanwhile, the Judd-Ofelt intensity parameters Ωt(t = 2,4,6), spontaneous radiative transition probabilities, fluorescence branching ratios and radiative lifetimes of relevant excited levels of Tm3+ ions were calculated based on the Judd-Ofelt theory to reveal the improved effects of Ag NPs on the 1.85 μm band spectroscopic properties. An improvement by about 75% of fluorescence intensity is found in the studied Er3+/Tm3+ co-doped tellurite glass containing 1.0 mol% amount of Ag NPs, and the thermal stability of glass host increases slightly with the Ag NPs while the glass structure maintains the amorphous nature. The above results indicate that the prepared Er3+/Tm3+ co-doped tellurite glass with an appropriate amount of Ag NPs is a promising host material applied for 1.85 μm band solid-state lasers and amplifiers.

Thermo-optical and spectroscopic properties of Nd:YAG fine grain ceramics: towards a better performance than the Nd:YAG laser crystals

In this work, we investigated the thermo-optical properties of highly Nd3+ doped YAG ceramics. The normalized lifetime thermal lens method was used to obtain the fluorescence quantum efficiency (η) versus Nd3+ concentration (Nt) and to study the energy transfer microparameters CDD and CDA. The Nt dependence of η was compared to the results of the previous literature. The CDA found is very similar to those of the previous literature, while the CDD is very different and higher than CDA, although the main dependence of η with Nt is assigned to CDA. The figure of merit (η.Nt versus Nt) indicated a maximum around 3.8 at.% Nd2O3, which in addition to the very low ds/dT value, evidences the YAG ceramic as an excellent material for an ultra-high-power microchip laser system and for devices requiring minimum pump-induced local heating generation.

The 1.53 μm spectroscopic properties of Er3+/Ce3+/Yb3+ tri-doped tellurite glasses containing silver nanoparticles

The metallic silver nanoparticles (NPs) was introduced into the Er3+/Ce3+/Yb3+ tri-doped tellurite glasses with composition TeO2–ZnO–La2O3 to improve the 1.53μm band fluorescence. The UV/Vis/NIR absorption spectra, 1.53μm band fluorescence spectra, fluorescence lifetimes, X-ray diffraction (XRD) curves, differential scanning calorimeter (DSC) curves and transmission electron microscopy (TEM) image of tri-doped tellurite glasses were measured, together with the Judd–Ofelt intensity parameters, emission cross-sections, absorption cross-sections and radiative quantum efficiencies were calculated to investigate the effects of silver NPs on the 1.53μm band spectroscopic properties of Er3+ ions, structural nature and thermal stability of glass hosts. It is shown that Er3+/Ce3+/Yb3+ tri-doped tellurite glasses can emit intense 1.53μm band fluorescence through the combined energy transfer (ET) processes from Yb3+ to Er3+ ions and Er3+ to Ce3+ ions under the 980nm excitation. At the same time, the introduction of an appropriate amount of silver NPs can further improve the 1.53μm band fluorescence owing to the enhanced local electric field effect induced by localized surface Plasmon resonance (LSPR) of silver NPs and the possible energy transfer from silver NPs to Er3+ ions, and an improvement by about 120% of fluorescence intensity is found in the studied Er3+/Ce3+/Yb3+ tri-doped tellurite glass containing 0.5mol% amount of silver NPs with average diameter of ∼15nm. The energy transfer mechanisms from Yb3+ to Er3+ ions and Er3+ to Ce3+ ions were also quantitatively investigated by calculating energy transfer microparameters and phonon contribution ratios. Furthermore, the thermal stability of glass host increases slightly with the introduction of silver NPs while the glass structure maintains the amorphous nature. The results indicate that the prepared Er3+/Ce3+/Yb3+ tri-doped tellurite glass with an appropriate amount of silver NPs is an excellent gain medium applied for 1.53μm band EDFA pumped with a 980nm laser diode (LD).

Quantitative Analysis of Energy Transfer and Origin of Quenching in Er(3+)/Ho(3+) Codoped Germanosilicate Glasses.

The energy transfer mechanism between Ho(3+) and Er(3+) ions has been investigated in germanosilicate glass excited by 980 nm laser diode. A rate equation model was developed to demonstrate the energy transfer from Er(3+) to Ho(3+) ions, quantitatively. Energy transfer efficiency from the Er(3+):(4)I13/2 to the Ho(3+):(5)I7 level can reach as high as 75%. Such a high efficiency was attributed to the excellent matching of the host phonon energy with the energy gap between Er(3+):(4)I13/2 and Ho(3+):(5)I7 levels. In addition, the energy transfer microparameter (CDA) from Er(3+):(4)I13/2 to Ho(3+):(5)I7 level was estimated to (4.16 ± 0.03) × 10(-40) cm(6)·s(-1) via the host-assisted spectral overlap function, coinciding with the CDA (2,88 ± 0.04) × 10(-40) cm(6)·s(-1) from decay analysis of the Er(3+):(4)I13/2 level which also indicated hopping migration-assisted energy transfer. Furthermore, the concentration quenching of Ho(3+):(5)I7 → (5)I8 transition was the dipole-dipole interaction in the diffusion-limited regime, and the quenching concentration of Ho(3+) reached 4.13 × 10(20) cm(-3).