Upconversion Emission Of Er3 Research Articles

Multicolor upconversion luminescence of dye-coordinated Er3+ at the interface of Er2O3 and CaF2 nanoparticles

ABSTRACT Multicolor upconversion luminescence of Er3+ was successfully enhanced by optimizing the interface in dye-coordinated nanoparticles with a core/shell structure. Red and green upconversion emissions of Er3+ were obtained at the interface of oxide nanoparticles via the intramolecular energy transfer from the coordinating squaraine dye with high light-absorption ability, which was more efficient than emissions through the energy transfer from metal ions such as Yb3+. Additionally, CaF2 nanoparticles as a core material minimized the energy loss with nonradiative downward relaxations in Er3+, resulting in the observation of unusual blue upconversion emissions from the upper energy level of Er3+ by nonlaser excitation using a continuous-wave (CW) Xe lamp at an excitation power of 1.2 mW/cm2.

Enhanced upconversion emissions in Er3+ doped perovskite BaTiO3 glass-ceramics via electric-stimulated polarization technique

In this work, Er3+ doped ferroelectric glass ceramics containing high-content BaTiO3 nanoperovskite have been prepared successfully. Optical behaviors with structural dependence indicate that the perturbation of ligand field by tunable thermal condition in glass-ceramics is beneficial to boost upconversion efficiency, that is, the emission intensity possesses multifold improvement in both green band (2H11/2, 4S3/2 → 4I15/2) and red band (4F9/2 → 4I15/2). And adding voltage to stimulate polarization reversal of ferroelectric domains has been investigated as a physical mode to broaden luminescence emissions in visible range. Compared with the unpolarized glass-ceramics, over 1.5 folds higher luminescence intensity can be obtained by polarizing the samples. The multiple mechanisms to achieve upconversion enhancement in ferroelectric materials will stimulate and expand the use of innovative optoelectronic devices.

Near-Infrared to Visible Upconversion Emission in Er3+ and Yb3+ Codoped BaHfO3

We report on the upconversion (UC) emission property of Er3+ and Yb3+ codoped BaHfO3 polycrystals. We observed the green (~ 540 nm) and the red (~ 660 nm) UC emissions in Er3+ in the host material BaHfO3 with 980-nm near-infrared excitation. These emissions exhibited strong temperature evolutions. Interestingly, the UC emissions in Er3+ were found to be controlled with the Yb3+ doping. In Er3+ and Yb3+ codoped BaHfO3, the intensity of the red UC emission increased dramatically while that of the green UC emission showed a non-monotonic temperature dependence. These results suggested that the UC emission process in the Er3+ ion in BaHfO3 should be temperature-sensitive.

Strong upconversion emissions in Er3+ doped Y2O3 nanocrystals prepared using a “PMMA-polymerization” route

A series of Er3+-doped Y2O3 nanocrystals were prepared by using a “polymethyl methacrylate (PMMA) polymerization” route. Under 975 nm excitation, upconversion emissions of the materials had been studied in details. The strong upconversion emissions have been observed in the Er3+-doped Y2O3 nanocrystals. The preparation method of luminescent nanocrystals will be helpful to the development of luminescent technology.

Enhanced upconversion emission of Er3+/Yb3+ and Er3+/Yb3+/Zn2+ doped calcium aluminate for use in optical thermometry and laser induced optical heating

There are two key factors to design an efficient green upconversion (UC) emission based optical sensor for temperature. The primary need is to develop a thermally stable and economical material, for a stable sensor, and the second essence is to get an efficient green UC emission, for high sensitivity of the sensor. The proof of this concept is demonstrated on a model system CaAl2O4: Er3+, co-doped with Yb3+ and Zn2+. UC emission of Er3+ ion is enhanced, primarily, through co-operative energy transfer from Yb3+ to Er3+ ions. Secondly, we prove that, incorporation of Zn2+ ions alters local crystal field environment around Er3+ ions which causes an enhancement in green UC emission. The variation in intensity ratio of 2H11/2 → 4I15/2 (green) and 4S3/2 → 4I15/2 (green) transitions with temperature is studied to report the sensing property. We show that, sensitivity becomes better with an increase in UC efficiency and the best sensitivity is attained for CaAl(0.793)2Er0.007Yb0.05Zn0.15O4 sample, ∼0.0154 K−1 at 308 K. The obtained result is compared with other works and implies its better suitability. Further, the laser induced optical heating is also observed. The laser induced optical heating has been observed experimentally at 400 K above 1 W laser power. This has been further verified by theoretical justification of heating at various pump powers.

Fabrication, microstructure, and temperature sensing behavior based on upconversion luminescence of novel Er3+,Yb3+ co-doped YOF ceramic

Novel YOF:Er,Yb ceramic was successfully fabricated by vacuum hot-press sintering method for the first time, and its phase, microstructure and upconversion luminescence were investigated. It was found that the ceramic showed very dense microstructure with few pores. Under 980 nm excitation, strong green (526 nm and 546 nm) and red (668 nm) upconversion emissions of Er3+ ions in the ceramic were observed. The upconversion mechanism was proposed based on the power dependence of the upconverted emissions. In addition, the temperature sensing behavior of the YOF:Er,Yb ceramic was investigated from 293 K to 873 K by using the fluorescence intensity ratio technique, and the maximum absolute sensitivity is 0.00882 K−1 at 873 K and the maximum relative sensitivity is 1.35% K−1 at 293 K. These results indicate that the fabricated YOF:Er,Yb ceramic is promising host material for optical temperature sensors.

Optical thermometry based on green upconversion emission in Er3+/Yb3+ codoped BaGdF5 glass ceramics

Er3+/Yb3+ codoped BaGdF5 glass ceramics have been prepared and used to develop a portable all-fiber temperature sensor based on fluorescence intensity ratio technique. XRD and TEM results affirm the generation of BaGdF5 nanocrystals in the borosilicate glass. Eu3+ ions are used as spectral probe to investigate external environment around rare earth (RE) ions. Intense green upconversion emissions from Er3+ ions are detected in the BaGdF5 glass ceramics and their intensity are enhanced about three orders of magnitude after heat treatment, which is attributed to the enrichment of RE ions in the BaGdF5 phase. Based on green upconversion emission from Er3+ ions, the temperature sensing property of the portable all-fiber temperature sensor is studied. The maximum absolute sensitivity is 15.5 × 10−4 K−1 at 567 K and the relative sensitivity is 1.28% K−1 at 298 K, respectively.

A novel strategy for markedly enhancing the red upconversion emission in Er3+/Tm3+ cooperated nanoparticles

A novel core–shell structured nanocrystal with energy trapping centers of Tm3+ ions doped in the Er3+-hosted core zone and Yb3+ ions doped in the shell portion is innovated to achieve super-bright red upconversion emission upon low 980 nm laser excitation.

Improvement of thermal and spectroscopic behavior of Er3+/Ce3+ co-doped tellurite glass for lasing materials

Tellurite glasses (TeO2–ZnO–Nb2O5) mono-doped Er3+ and co-doped Er3+/Ce3+ have been prepared using the melt-quenching technique. To evaluate the effect of Ce3+ on the structural, thermal stability of glass hosts and fluorescence properties of Er3+, X-ray diffraction patterns, Ftir spectra, differential scanning calorimeter curves, absorption spectra, fluorescence emission spectra, fluorescence lifetimes, up-conversion emission spectra of glass samples were measured and investigated. Using Judd–Ofelt theory, we calculated intensity parameters (Ω2, Ω4 and Ω6), spontaneous emission probabilities, the radiative lifetime, luminescence branching factors and the quantum yield of luminescence for 4I13/2 → 4I15/2 transition. The co-doping with Ce3+ was effective on the suppression of up-conversion emission of Er3+ owing to the phonon-assisted energy transfer: Er3+:4I11/2 + Ce3+:2F5/2 → Er3+:4I13/2 + Ce3+:2F7/2 which contributed the effective enhancement of 1.53 µm fluorescence emission. The change in optical properties with the addition of Ce3+ ions have been discussed and compared with other glasses. Using the Mc Cumber method for the 4I13/2 → 4I15/2 transition, absorption cross-section, calculated emission cross-section, and gain cross-section values support that TZNEr1Ce1 glass is a potential material for developing broad-band and high-gain erbium-doped fiber amplifiers applied for 1.53 µm.

A Point Temperature Sensor Based on Upconversion Emission in Er3+/Yb3+ Codoped Tellurite-Zinc-Niobium Glass.

Er3+/Yb3+ codoped tellurite-zinc-niobium (TZNb) glass was prepared by the melt-quenching method and used for the construction of a point all-fiber temperature sensor. The glass thermal stability and network structural properties were studied by differential thermal analysis and Raman spectrum, respectively. High glass transition temperature is beneficial to widen the working temperature range. The dependence of fluorescence intensity ratio (FIR) of green upconversion emissions on the surrounding temperature from 276 to 363 K was experimentally investigated and the maximum temperature sensitivity is 95 × 10−4 K−1 at 363 K. Strong green upconversion emission, broad temperature measurement range and high sensitivity indicate this point temperature sensor is a promising optical device for application on optical temperature sensing.

Enhancement of upconversion emission in Er:LiNbO3 by codoping with HfO2 under 1550 nm excitation

An increased red upconversion emission produced under excitation at 1550 nm was observed in hafnium and erbium co-doped lithium niobate (Hf (8 mol%)/Er:LiNbO3), which can be used to increase the photovoltaic efficiency of solar cells. Three 1550 nm photons were required to arouse the green and red emissions in Hfx(x= 2, 4, 6 mol%)/Er:LiNbO3, while the red emitting 4F9/2 state was populated by a hybrid two- and three-photon process in Hf(8 mol%)/Er:LiNbO3. The formation of Er3+ cluster sites (ErLi2+-ErNb2−) lead to an efficient cross relaxation process 4I13/2 + 4I13/2 → 4I15/2 + 4I9/2 and enhanced red emission in Hf(8 mol%)/Er:LiNbO3.

Unraveling the correlation between oxide-ion motion and upconversion luminescence in β-La2Mo2O9:Yb3+,Er3+ derivatives

The upconversion emission of Er3+ in β-La2(Mo,W)2O9 can reveal the short-range thermally-driven jumps and long-range motion of oxide-ions.

Up-conversion emission of Er3+/Yb3+co-doped BaBi2Nb2O9 (BBN) phosphors

On this paper, polycrystalline samples of the tetragonal systems BaBi2Nb2O9 (BBN) and BBN co-doped with Er3+/Yb3+ (BBN: 0.04Er3+yYb3+, where y=0.02, 0.04, 0.06 and 0.08mol%) were synthesized by the solid state method. The crystalline structure and photoluminescent properties of the ceramic phosphors were investigated by powder X-ray diffraction (PXRD), Raman spectroscopy and spectral analysis of up-conversion (UC) emission. The results reveal that all compositions crystallize in the I4/mmm space group at room temperature, and show UC green emissions (centered at 525nm and 550nm) and red (around 660nm) coming from (2H11/2, 4S3/2→4I15/2) and (4F9/2→4I15/2) transitions, respectively, under excitation at 980nm. Increasing variations of the Yb3+ sensitizer concentration in the host BBN, lead to a significant intensity increase in both UC emissions due to the efficiency of the energy-transfer process. The BBN: 0.04mol%Er3+0.08mol%Yb3+ composition showed the higher intensity bands, thus establishing the BBN as an alternative host material for luminescent centers.

The effects of Ho3+ and Pr3+ ions on the spectroscopic properties of Er3+ doped SrGdGa3O7 crystals used in mid-infrared lasers

Ho3+ and Pr3+ ions were introduced into Er3+ : SrGdGa3O7 crystal, respectively, for enhanced 2.7 μm emissions. The effects of Ho3+ and Pr3+ on the spectroscopic properties and mutual energy transfer mechanisms were investigated. It is found that the introductions of Ho3+ and Pr3+ are helpful to achieve enhanced mid-infrared emissions and reduced near-infrared emissions. The up-conversion emission in Er3+/Ho3+ : SrGdGa3O7 crystal was stronger than that in Er3+ : SrGdGa3O7 crystal, while that in Er3+/Pr3+ : SrGdGa3O7 crystal was decreased. Introducing Ho3+ and Pr3+ depopulated the lower laser lever through energy transfer and thus reduced the fluorescence lifetime of Er3+ : 4I13/2 in Er3+/Ho3+ : SrGdGa3O7 and Er3+/Pr3+ : SrGdGa3O7 crystals to 1/2 and 1/10 of that in Er3+ : SrGdGa3O7 crystal without significantly affecting the fluorescence lifetime of the upper laser level Er3+ : 4I11/2, which greatly reduces the self-saturation problem. However, with reduced up-conversion emission and a weaker self-termination effect, Pr3+ is a more appropriate sensitizer than Ho3+ for Er3+ in this crystal. All the results imply that Er3+/Pr3+ : SrGdGa3O7 crystal could act as a potential gain media for an enhanced 2.7 μm MIR laser.

Infrared-to-visible upconversion emission of Er3+/Yb3+-codoped SrMoO4 phosphors as wide-range temperature sensor

Er3+/Yb3+-codoped SrMoO4 phosphors were prepared by a high-temperature solid-state reaction method. At room temperature, all the as-prepared samples exhibited strong upconversion properties and the emission intensity increased dramatically with the increase of Yb3+ ion concentration, reaching its maximum value when the concentration was 5 mol%. The dependence of emission intensity on the pump power suggested that the upconversion emission was a two-photon process. Furthermore, the optical temperature sensing properties based on green upconversion emissions of the SrMoO4:0.01Er3+/0.05Yb3+ phosphor were studied. It is found that the SrMoO4:0.01Er3+/0.05Yb3+ phosphor can be operated over a very wide temperature range of 93–773 K with a maximum sensitivity of ∼0.0128 K−1, indicating that low- and high-temperature thermometry can be simultaneously realized in this phosphor.

2 μm fluorescence of Ho3+:5I7 → 5I8 transition sensitized by Er3+ in tellurite germanate glasses

This paper investigated the mid-infrared luminescence properties of Er3+/Ho3+ co-doped tellurite germanate glass at 2μm pumped by 980nm. Thermal stability of the system, absorption spectra and fluorescence spectra of the Er3+/Ho3+ co-doped glass sample were measured. Besides, the absorption spectra of the Ho3+ singly doped sample was measured. According to the measured absorption spectra and the Judd–Ofelt theory, the Judd–Ofelt intensity parameters Ωt (t=2,4,6), spontaneous radiative transition probability, branching ratio and lifetime of Ho3+ were calculated. And the upconversion emission in Er3+ doped and Er3+/Ho3+ co-doped tellurite germanate glasses pumped by 980nm have been investigated. Then the spectroscopic properties and possible energy transfer mechanisms between Ho3+ and Er3+ ions were discussed in detail. Meanwhile, the FWHM (146nm), σepeak×FWHM (659.92cm3) and emission cross section (4.52×10−21cm2) of 5I8→5I7 transition of Ho3+ were obtained, respectively. The results indicate that Er3+/Ho3+ co-doped tellurite germanate glass is a promising host material for 2μm solid laser.

A temperature dependent investigation of upconversion emission in Er3+:PLZT transparent ceramic

The upconversion emission of Er3+:PLZT transparent ceramic was investigated at different temperatures from 10 to 300K. Emission bands around 540, 564 and 682nm corresponding to transitions from 2H11/2, 4S3/2, and 4F9/2 to 4I15/2 were observed. As the measurement temperature was increased, the intensities of the 564 and 682nm peaks decreased, while that of the 540nm peak increased. Based on the rate equation theory, a model for the dynamics of upconversion emission in Er3+:PLZT ceramic was proposed. Impressively, the calculations agree well with the experimental data in the whole temperature range. Additionally, the temperature dependent upconversion emission behavior in Er3+:PLZT ceramic was discussed in terms of the Boltzmann thermal distribution and nonradiative relaxation.

Multiple temperature effects on up-conversion fluorescences of Er3+-Y b3+-Mo6+ codoped TiO2 and high thermal sensitivity

We report multiple temperature effects on green and red up-conversion emissions in Er3+-Y b3+-Mo6+ codoped TiO2 phosphors. With increasing temperature, the decrease of the red emission from 4F9/2→4I15/2, the increase of green emission from 2H11/2→4I15/2 and another unchanged green emission from 4S3/2→4I15/2 were simultaneously observed, which are explained by steady-state rate equations analysis. Due to different evolution with temperature of the two green emissions, higher thermal sensitivity of optical thermal sensor was obtained based on the transitions with the largest fluorescence intensity ratio. Two parameters, maximum theoretical sensitivity (Smax) and optimum operating temperature (Tmax) are given to describe thermal sensing properties of the produced sensors. The intensity ratio and energy difference ΔE of a pair of energy levels are two main factors for the sensitivity and accuracy of sensors, which should be referred to design sensors with optimized sensing properties.

Enhanced upconversion emission of three dimensionally ordered macroporous films Bi2Ti2O7:Er3+, Yb3+ with silica shell

In this paper, a simple effective approach has been developed to enhance upconversion emission of three-dimensionally ordered macroporous materials, which is attributed to formation of silica shell around surface of three-dimensionally ordered macroporous materials. This approach involves the preparation of Bi2Ti2O7:Er3+, Yb3+ three-dimensionally ordered macroporous materials and the formation of amorphous SiO2 shell on the macroporous surfaces of three-dimensionally ordered macroporous materials. The influence of silica shell on the upconversion emission of Er3+ ions was investigated, and the enhanced upconversion emission was observed in the Bi2Ti2O7:Er3+, Yb3+ three-dimensionally ordered macroporous materials owing to the suppression of surface quenching effect caused by the formation of silica shells.

Concentration effects on the FIR technique for temperature sensing

Different concentrations of Er3+ doped Y2O3 ceramics are synthesized. Under the 966nm excitation, it is found that the ratios of red to green emissions are obviously enhanced with temperature for high doped sample, which is attributed to the combined temperature-dependent processes. Besides that, variations of fluorescence intensity ratio of green upconversion emissions in Er3+:Y2O3 ceramics have been studied as a function of temperature. A maximum sensitivity of less than 0.003K−1 is obtained in the high doped sample, whereas it is above 0.005K−1 in the low doped sample. Concentration effects on the temperature sensing behaviors are discussed. In addition, similar phenomenon is found in Er3+/Yb3+ codoped NaYF4 nanocrystals.