Codoped Tellurite Glasses Research Articles

Spectroscopic properties of tellurite glasses co-doped with Er3+ and Yb3+

Spectroscopic characterization of Er3+/Yb3+ co-doped tellurite glasses 70.8TeO2–5Al2O3–13K2O–(11−x)–BaO–0.2Er2O3–xYb2O3, where x=0, 0.4, 0.8, 1.2 and 2mol% has been carried out through X-ray diffraction, Raman, absorption and luminescence spectra. The Judd–Ofelt intensity parameters were calculated for 0.2mol% Er3+-doped glass and are used to evaluate radiative properties such as transition probabilities, branching ratios and radiative lifetime. The emission cross-section of the 4I13/2→4I15/2 transition has been calculated from the absorption data using McCumber׳s theory. The emission intensity of both, visible and infrared signals as a function of Yb2O3, have been studied under 980nm and 375nm laser excitation. The physical mechanisms responsible for both, visible and infrared signals in the tellurite samples have been explained in terms of the energy transfer and excited state absorption process. The FWHM of the 4I13/2→4I15/2 transition as a function of Yb2O3 mol% and distance (δ) between the laser focusing point and the end-face of the glass has been reported. It was observed both, experimentally and numerically, a change in the FWHM with variations of δ less than 8mm. The latter was attributed to the radiation trapping effect.

Intense visible upconversion and energy transfer in Ho3+/Yb3+ codoped tellurite glasses for potential fiber laser

New Ho3+/Yb3+ codoped tellurite glasses (TeO2–Bi2O3–ZnO–Na2O) prepared by melt-quenching technique were investigated to realize visible-band upconversion emissions applied for compact fiber lasers. The absorption spectra, upconversion emission spectra, differential scanning calorimetry (DSC) curves, X-ray diffraction (XRD) and Raman spectra were measured to characterize the spectroscopic properties of Ho3+, thermal stability and structural nature of glass hosts. Under the excitation of 980nm laser diode (LD), the intense green (∼543nm) and red (∼657nm) upconversion emissions corresponding to 5F4(5S2)→5I8 and 5F5→5I8 transitions of Ho3+ respectively are simultaneously observed. The power dependence study of upconversion intensities on excited pump power revealed that the Ho3+ population at 5F4(5S2) and 5F5 levels was originated from two-photon absorption process based on the energy transfer from Yb3+ to Ho3+. The energy transfer mechanism from Yb3+ to Ho3+ was investigated and relevant micro-parameters (energy transfer coefficient and critical radius) and phonon contribution ratio were presented. With the increase of Yb3+ doped concentration, both the green and red upconversion intensities enhanced greatly, meanwhile the thermal stability of glass hosts, characterized by the three characteristic temperatures, also got a slight improvement. Furthermore, the glass structure was briefly analyzed with the calculated Judd–Ofelt intensity parameters, the measured Raman spectra and XRD curves. The present results indicate that the new synthesized Ho3+/Yb3+ codoped tellurite glass with intense green and red upconversion emissions is a promising medium applied for the visible-band fiber lasers.

Luminescence Properties of Ce/Tb/Sm Co-Doped Tellurite Glass for White Leds Application

Luminescence Properties of Ce/Tb/Sm Co-Doped Tellurite Glass for White Leds Application

Enhanced 2 µm fluorescence and thermal stability in Ho3+/Tm3+ codoped WO3 modified tellurite glasses

A certain amount of WO3 oxide was introduced into the Ho3+/Tm3+ codoped tellurite glass, and the absorption spectra, fluorescence spectra, Raman spectra, X-ray diffraction patterns and differential scanning calorimeter curves were measured to illustrate the enhanced effects of WO3 on the 2µm fluorescence of Ho3+ and thermal stability of glass host. Under the excitation of 808nm LD, the 2µm fluorescence of Ho3+ increases obviously with the partial substitution of TeO2 by WO3 oxide, which is attributed to the enhanced energy transfer process from Tm3+:3F4 to Ho3+:5I7 level by providing a relatively large phonon energy. Meanwhile, the thermal stability of glass host increases accordingly, which is mainly attributed to the formation of thermal stability W=O bond. The intense 2µm fluorescence together with good thermal stability indicates that Ho3+/Tm3+ codoped WO3 modified tellurite glass is a potential laser glass for efficient 2µm emission.

Photoluminescence study of Sm3+–Yb3+co-doped tellurite glass embedding silver nanoparticles

We report on the upconversion emission of Sm3+ ions doped tellurite glass in the presence of Yb3+ ions and silver nanoparticles. The enhancement of infrared-to-visible upconversion emissions is achieved under 980nm excitation wavelength and attributed to the high absorption cross section of Yb3+ ions and an efficient energy transfer to Sm3+ ions. Further enhancements are attributed to the plasmonic effect via metallic nanoparticles resulting in the large localized field around rare earth ions. However, under excitation at 406nm, the addition of Yb3+ content and heat-treated silver nanoparticles quench the luminescence of Sm3+ ions likely due to quantum cutting and plasmonic diluent effects, respectively.

On observation of the downconversion mechanism in Er3+/Yb3+ co-doped tellurite glass using thermal and optical parameters

In this work we report the observed downconversion (DC) mechanism in Er3+/Yb3+-codoped tellurite glasses (in mol%, 80TeO2–10Li2O–10TiO2). The samples were synthesized by the conventional melt-quenching method and then studied using optical spectroscopy and thermal lens spectroscopy (TLS). These characterizations enabled investigation of the radiative and nonradiative processes involved in energy transfer from erbium to ytterbium. The visible Er3+ fluorescence intensities decreased as a function of the Yb3+ concentration, and there was a corresponding increase in the ytterbium emission at around 980nm. Simultaneously, there was a reduction in the heat-generated due nonradiative decays (~21%) when ytterbium was added. This temperature change was measured by TLS measurements and the results corroborate with the indicated by spectroscopic interpretation.

Enhanced 2.7 μm mid-infrared emission and energy transfer mechanism in Er3+/Nd3+ codoped tellurite glass

Nd3+ was introduced into Er3+ doped tellurite glass with composition of TeO2Nb2O5ZnONa2O to improve the 2.7μm band fluorescence upon the excitation of 800nm LD. The DSC curve and Raman spectrum were measured to characterize the thermal stability and vibration nature of glass host. The absorption spectra, visible, near- and mid-infrared fluorescence emission spectra were measured to evaluate the effects of Nd3+ introduction on the spectroscopic properties especially the 2.7μm band fluorescence of Er3+. It is shown that the prepared tellurite glass exhibits a large glass transition temperature and no obvious crystallization peak is observed in the measured temperature range of 200–550°C. Moreover, the introduction of Nd3+ significantly improves the 2.7μm band fluorescence intensity through joint energy transfer processes between the relevant excited levels of Er3+ and Nd3+, and the energy transfer mechanisms are further investigated in detail by calculating energy transfer micro-parameters and efficiency. The excellent thermal stability and strong 2.7μm fluorescence emission aroused by adopting codoping scheme indicate that the prepared Er3+/Nd3+ codoped tellurite glass is a potential glass medium applied for the 2.7μm mid-infrared band lasers.

Control of the radiative properties via photon-plasmon interaction in Er3+ -Tm3+ -codoped tellurite glasses in the near infrared region.

The novelty of this paper is that it reports on the tuning of the spectral properties of Er3+ -Tm3+ ions in tellurite glasses in the near-infrared region through the incorporation of silver or gold nanoparticles. These noble metal nanoparticles can improve the emission intensity and expand the bandwidth of the luminescence spectrum centered at 1535 nm, covering practically all the optical telecommunication bands (S, C + L and U), and extended up to 2010 nm wavelength under excitation by a 976 nm laser diode. Both effects are obtained by the combined emission of Er3+ and Tm3+ ions due to efficient energy transfer processes promoted by the presence of silver or gold nanoparticles for the (Er3+)4I(11/2)→(Tm3+)3H5, (Er3+)4I(13/2)→(Tm3+)3H4 and (Er3+)4I(13/2)→(Tm3+)3F4 transitions. The interactions between the electronic transitions of Er3+ and Tm3+ ions that provide a tunable emission are associated with the dynamic coupling mechanism described by the variations generated by the Hamiltonian H DC in either the oscillator strength or the local crystal field, i.e. the line shape changes in the near-infrared emission band. The Hamiltonian is expressed as eigenmodes associated with the density of the conduction electron generated by the different nanoparticles through its collective free oscillations at each resonance frequency of the nanoparticle and their geometric dependence. A complete description of photon-plasmon interactions of noble metal nanoparticles with the Er3+ and Tm3+ ions is provided.

Enhanced green upconversion by controlled ceramization of Er3+–Yb3+ co-doped sodium niobium tellurite glass–ceramics for low temperature sensors

Tellurite based glasses are well-known for their upconversion properties besides having a disadvantage of low mechanical strength dragging them away from practical applications. The present work deals with preparation of sodium niobium tellurite (SNT) glasses using melt quenching method, in which small quantities of boron and silicon in the form of oxides are added to improve their mechanical properties. Controlled heat treatment is performed to ceramize the prepared glasses based on the thermal data given by DTA. XRD and SEM profiles of the glass–ceramics which confirmed the formation of crystalline monoclinic Sodium Tellurium Niobium Oxide (Na1.4Nb3Te4.9O18) phase (JCPDS card No. 04–011-7556). Upconversion measurements in the visible region were made for the prepared Er3+–Yb3+ co-doped glasses and glass–ceramics with 980nm laser excitation varying the laser power and concentration of Er3+ ions. Results showed that the upconversion luminescence intensity was enhanced by ten times in SNT glass–ceramics compared to that in the SNT glasses. Decay curves give evidence of high performance of glass–ceramics compared to glasses due to ceramization and structural changes. Temperature dependent visible upconversion was performed to test the ability of efficient SNT glass–ceramic at low temperatures and variation of upconversion intensities was studied.

Enhanced 1.8 μm emission in Yb3+/Tm3+ codoped tungsten tellurite glasses for a diode-pump 2.0 μm laser

Enhanced 1.8μm emission from Tm3+ by Yb3+ sensitization and bubbling in tungsten tellurite glasses has been demonstrated under the excitation of a 976nm laser diode. Radiative properties such as spontaneous emission probabilities, radiative lifetimes and fluorescence branching ratios along with absorption and emission cross sections have been calculated from the absorption spectra. The influences of Yb3+ concentration, Tm3+ concentration, and bubbling time on spectroscopic properties have been thoroughly investigated. It is found that with increasing the bubbling time to 35min, OH− content deceases sharply while 1.8μm emission intensity improves greatly and 3F4 level lifetime prolongs to 1.57ms close to radiative time. After 35min, they change very little due to almost reaching the dynamic balance. The strength of interaction between Tm3+ and OH− is determined. The energy transfer mechanism between Yb3+ and Tm3+ is proposed by photoemission spectroscopy and lifetime measurement. The energy transfer coefficients have been analyzed by the extended spectral overlap method and hopping model. Large ratio of the forward energy transfer from Yb3+ to Tm3+ to the backward one (223) and high energy transfer efficiency (97%) from Yb3+ to Tm3+ ensure efficient 1.8μm emission. Hence, Yb3+ sensitization and the reduction of OH− content could be expected to open up a possibility to achieve high efficient 2.0μm lasing from Tm3+ under a 976nm LD pump.

Multicolor upconversion emission and energy transfer mechanism in Er3+/Tm3+/Yb3+ codoped tellurite glasses

A novel Er3+, Tm3+ and Yb3+ codoped tellurite glasses with composition of TeO2–Bi2O3–ZnO–Na2O was prepared by conventional melt-quenching technique to realize the multicolor upconversion (UC) emissions. The absorption spectrum, UC emission spectrum, Raman spectrum, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) curves were measured to characterize the prepared glass samples. Under the excitation of 980nm laser diode (LD), bright multicolor luminescence composed of red, green and/or blue UC emissions corresponding to the transitions 4F9/2→4I15/2, 2H11/2(4S3/2)→4I15/2 of Er3+ and 1G4→3H6 of Tm3+ were observed in the Er3+/Yb3+, Tm3+/Yb3+ and Er3+/Tm3+/Yb3+ codoped glass samples, which were mainly attributed to the successive energy transfers from Yb3+ to Er3+ and Tm3+, respectively. The energy transfer mechanisms from the Yb3+:2F5/2 level to Er3+:4I11/2 and Tm3+:3H5 levels were further investigated by quantitatively calculating the energy transfer micro-parameters and phonon contribution ratios. Meanwhile, the difference (ΔT=Tx−Tg) between the glass crystallization onset temperature (Tx) and the transition temperature (Tg) which increase slightly with rare-earth (RE) doped concentration, was larger than 140°C for all glass samples. Furthermore, the amorphous nature of glass structure was demonstrated by the measured XRD curves. The excellent thermal stability and multicolor luminescent characteristic indicate that the present investigated Er3+/Tm3+/Yb3+ codoped tellurite glasses could be used in the fields of solid state multicolor displays and other luminescent devices.

Enhanced upconversion emissions in Ho3 +/Yb3 + codoped tellurite glasses containing silver NPs

Ho3+/Yb3+ codoped zinc-tellurite glasses containing silver nanoparticles (NPs) were prepared using the conventional melt-quenching technique. The detailed effect of silver NPs on the upconversion emission of Ho3+, thermal stability and structure behavior of glass hosts was investigated from the measured absorption spectra, upconversion emission spectra, differential scanning calorimeter (DSC) curves, X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images. Two frequency upconversion emission bands centered at 546nm (green) and 657nm (red) corresponding to Ho3+ transitions of 5F4(5S2)→5I8 and 5F5→5I8, respectively, are simultaneously observed under the 980nm excitation at room temperature. It is shown that the introduction of silver NPs can further improve the upconversion emissions of Ho3+and thermal stability of glass host, while the glass structure maintains the amorphous nature. The enhanced upconversion emission is mainly attributed to the increased local electric field around Ho3+induced by localized surface plasmon resonance (LSPR) effect of silver NPs. Furthermore, the energy transfer (ET) mechanism from Yb3+:2F5/2 level to Ho3+:5I6 level is quantitatively analyzed by calculating relevant micro- parameters and phonon contribution ratio.

Enhanced 1.8 μm emission in Yb3+/Tm3+ co-doped tellurite glass: Effects of Yb3+↔Tm3+ energy transfer and back transfer

The ~1.8μm emission characteristics of Tm3+ by a direct excitation and through an energy transfer process upon sensitization with Yb3+ ions in tellurite glass are reported. The spectroscopic properties of Tm3+ ions have been evaluated by applying Judd–Ofelt theory on the measured absorption spectrum. The obtained intensity parameters, Ω2=7.155×10−20cm2, Ω4=3.325×10−20cm2, Ω6=1.278×10−20cm2 are used to estimate the radiative properties of Tm3+ ions in the present glass host. A ~10 fold enhancement in the Tm3+ 1.8μm emission observed with 16 fold reduced emission of Yb3+ ions (1008nm) in co-doped sample on Yb3+ ions excitation illustrates the efficient energy transfer from Yb3+: 2F5/2→Tm3+: 3H5. The energy transfer process assisted by host phonon energy has been discussed by using relevant theoretical models and estimated the energy transfer micro-parameters. Effect of energy back transfer Tm3+→Yb3+ on NIR and upconversion emissions have been discussed. An efficient ~1.8μm with comparatively higher emission cross-section 1.115×10−20cm2 on account of reduced upconversion emissions has been achieved in the present tellurite glass.

Design and achieving of multicolor upconversion emission based on rare-earth doped tellurite

Yb3+/Tm3+ co-doped and Yb3+/Ho3+/Tm3+ tri-doped tellurite glasses were synthesized by fusing the mixture of TeO2, PbF2, AlF3, BaF2, Yb2O3, Tm2O3 and Ho2O3 in a corundum crucible at 850 °C for 20 min. The synthesized glasses were characterized by upconversion emission spectra under the excitation of 980 nm laser, and the emission colors were investigated according to the CIE-1931 standards. The results indicated that Yb3+/Tm3+ co-doped tellurite glass exhibited blue upconversion emission with favorable color coordinates of (0.20, 0.07). Yb3+, Ho3+ and Tm3+ tri-doped tellurite glasses presented white upconversion luminescence under a single 980 nm laser excitation. Moreover, a very wide range of emission colors could be tuned by altering Ho3+ concentration. Combining the contribution of adjusting Ho3+ concentration and pump power, near equal energy white light was obtained.

Tm3+/Ho3+/Yb3+ codoped tellurite glass for multicolor emission – Structure, thermal stability and spectroscopic properties

Tm3+, Ho3+ and Yb3+ codoped tellurite glasses (TeO2Bi2O3ZnONa2O) were prepared using conventional melt-quenching technique to realize the sensitized near-infrared to visible multicolor upconversion emission. The X-ray diffraction (XRD) curves, Raman spectra, differential scanning calorimeter (DSC) curves, absorption spectra and visible upconversion emission spectra were measured to characterize the structure nature, thermal stability and upconversion spectroscopic properties of rare earth (RE) codoped glass samples. Upon the excitation of 980nm laser diode (LD), the multicolor upconversion emissions were experimentally observed from the prepared glass samples owing to the intense blue (∼477nm) upconversion fluorescence of Tm3+ and green (∼544nm) and red (∼657nm) upconversion emissions of Ho3+, which have been attributed to the result of the multi-step energy transfer (ET) from Yb3+ to Tm3+ (and Ho3+) and excited state absorption (ESA). The ET mechanism between Yb3+:2F5/2 and Tm3+:3H5 (and Ho3+:5I6) levels were further investigated by calculating the micro-parameters (energy transfer coefficient CDA and critical radius RC). In addition, the glass transition temperature (Tg) increases with the RE doped concentration and the estimated difference (ΔT) between the onset crystallization temperature (Tx) and the glass transition temperature (Tg) for all glass samples is larger than 140°C, while the glass structure maintains the amorphous nature. The excellent thermal stability and multicolor emission characteristics with RE doped concentration indicate that the studied Tm3+/Ho3+/Yb3+ codoped tellurite glasses could be used in the fields of solid state multicolor displays and illumination devices.

Silver nanoparticles enhanced 1.53 µm band fluorescence of Er3+/Yb3+ codoped tellurite glasses

The silver nanoparticles (NPs) was introduced into the Er3+/Yb3+ codoped tellurite glasses with composition of TeO2–ZnO to improve the 1.53µm band fluorescence of Er3+ and the thermal stability of glass host. The UV–Vis–NIR absorption spectra, 1.53µm band fluorescence spectra and fluorescence decaying curves, the differential scanning calorimeter (DSC) curves, X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images of glass samples were characterized to investigate the effect of silver NPs on the fluorescence properties of Er3+, thermal stability and structure behavior of glass host. It is shown that the Er3+/Yb3+ codoped tellurite glass emits intense 1.53µm band fluorescence with peak wavelength located at about 1532nm under the 980nm excitation. The introduction of silver NPs further improves the fluorescence intensity of Er3+ which is attributed 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+. An improvement by about 62% of 1.53µm band fluorescence intensity was found in the studied Er3+/Yb3+ codoped tellurite glass containing 0.5mol% amount of AgNO3. In addition, the thermal stability of glass host increases with the introduction of silver NPs while the glass structure maintains the amorphous nature. The present results indicate that the prepared Er3+/Yb3+ codoped tellurite glass with an appropriate amount of silver NPs has good prospect as a gain medium applied for 1.53µm band broad and high-gain erbium-doped fiber amplifiers (EDFAs).

Influence of temperature on upconversion luminescence in tellurite glass co-doped with Yb3+/Er3+ and Yb3+/Tm3+

The fluorescence intensity ratio (FIR) of the green upconversion in Yb3+/Er3+ and blue upconversion in the Yb3+/Tm3+ co-doped tellurite glass as a function of temperature in the range of 20–220°C was investigated. The influence of temperature on FIR upconversion emission spectra of the thermally coupled Er3+: 2H11/2 and 4S3/2 levels enabled to achieve maximum sensitivity of 0.0036°C−1 at 225°C. Despite the lack of thermally coupled levels Yb3+/Tm3+ co-doped tellurite glass is proposed for construction of a temperature sensor. The maximum sensitivity of 0.0044°C−1 at 240°C was obtained using the FIR technique of the upconversion emission at 651nm (Tm3+: 1G4→3F4) and 698nm (Tm3+: 3F3→3H6).

Tm3+-Yb3+ Codoped Lithium-Titanate Tellurite Glasses

The optical behaviour of Tm3+-Yb3+ codoped tellurite glass in presence of Li2CO3 and TiO2 modifiers, prepared by conventional melt and quench technique has been investigated with the help of NIR-Visible UC study. The generation of the visible UC bands around ∼ 476nm, ∼702nm, ∼795nm and a weak peak around ∼ 653nm, due to the 1G4→ 3H6, 3F2→ 3H6, 3H4→ 3H6 and 1G4→ 3F4, transitions respectively under 980 nm excitation have been discussed in detail with the help of energy level diagram.

氟化物对Er3+/Yb3+共掺的碲酸盐玻璃上转换和红外发光性能的影响

Er3+/Yb3+ 共掺的碲酸盐玻璃由于其良好的上转换发光性能而得到广泛的研究。本文将氟化物引入碲酸盐玻璃中, 通过熔融法制备了量比为70TeO2-(30-x)ZnO-xZnF2-0.15Er2O3-1.5Yb2O3(x=0,5,10,15,20)的碲酸盐氧氟玻璃样品, 并测试其热稳定性、拉曼光谱以及受激发射光谱。实验结果表明, 随着氟化物含量的提高, Er3+离子的410,555,670 nm上转换发光和2~3 μm波段中红外发光得到增强, 并且红光提高强度比绿光和蓝光更明显。在分析了氟离子引入后对上转换与近中红外波段发光的内在影响机制发现: 碲酸盐玻璃系统中的氟化物一方面促进能量传递过程中Er3+离子的双光子吸收, 促进粒子跃迁至相应的高能级; 另一方面, 引入氟化物后的碲酸盐玻璃的最大能量声子态密度下降也是降低无辐射跃迁概率、提高上转换和中红外发射强度的重要原因。

Er3+单掺与Er3+/Pr3+共掺碲酸盐玻璃的2.7 μm光谱性质及能量转移过程

Er³⁺单掺与Er³⁺/Pr³⁺共掺碲酸盐玻璃的2.7 μm光谱性质及能量转移过程