Yellow upconversion luminescence in Ho3＋/yb3＋ co-doped Gd2Mo3O9 phosphor

The strong yellow upconversion (UC) light emission was observed in Ho3+/Yb3+co-doped Gd2Mo3O9 phosphor under the excitation of 980 nm diode laser. The phosphors were synthesized by the traditional soli...     

White up-conversion luminescence and highly-sensitive optical temperature sensing in Na3La(VO4)2:Yb,Er,Tm,Ho phosphors

In this work,tunable white up-conversion luminescence was achieved in the Yb³⁺,Er³⁺,Tm³⁺,Ho³⁺ codoped Na₃La(VO₄)₂ phosphors under 980 nm excitation.The emissions of three primary colors are mainly attributed to the ²H_11/2/⁴S_3/2→⁴I_15/2 transitions of Er³⁺,¹G₄→³H₆ transition of Tm³⁺,and_5...     

Promising light converting BaMoO4:Er3+-Tm3+-Yb3+ phosphors for display and optical temperature sensing

Er³⁺-Tm³⁺-Yb³⁺ tri-doped BaMoO₄ phosphors were synthesized by co-precipitation technique and characterized by X-ray diffraction analysis, absorption study and field emission scanning electron microscopy analysis. Upconversion as well as downconversion luminescence studies were performed by using near infrared (980 nm) and ultraviolet (380 nm) excitations. Energy level diagram, pump power dependence and colour coordinate study were utilized to describe the multicolor upconversion emission properties. Under single 980 nm diode laser excitation the dual mode sensing behaviour is realized via Stark sublevels and thermally coupled energy levels of the Tm³⁺ and Er³⁺ ions in the prepared tri-doped phosphors. A comparative fluorescence intensity ratio analysis for integrated emission intensities arising from the Stark sublevels {¹G_4(a) and ¹G_4(b)} and thermally coupled energy levels {²H_11/2 and ⁴S_3/2} of the Tm³⁺ and Er³⁺ ions, respectively was carried out in the prepared tri-doped BaMoO₄ phosphors. The maximum sensitivity for thermally coupled energy levels of the Er³⁺ and Stark sublevels of the Tm³⁺ ion was reported. The developed phosphors could be useful in the display devices and optical thermometric applications.     

Up-conversion luminescence properties of Yb^3＋ and Ho^3＋ co-doped Bi3.84W0.16O6.24 powder synthesized by hydrothermal method

Using polyethylene glycol (PEG) as the surfactant, Bi3.84W0.16O6.24 up-conversion luminescence nano-crystal co-doped with Yb3+ and Ho3+ ions was synthesized by the hydrothermal method. The structure and properties of luminescence powder were studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). It was of cubic system when the sample was synthesized at a low temperature and the particle size was about 30 nm. The results showed that adding surfactants was useful to improve the powder agglomeration and the grain crystal was spherical. The green emission peak at 546 nm and red emission peak at 655 nm, corresponding to the ( 5F4, 5S2)→ 5 I 8 and the 5 F 5 → 5 I 8 transitions of Ho 3+ , respectively, were simultaneously observed at room temperature under excitation of 980 nm semiconductor laser. The up-conversion luminescence intensity was the strongest when the concentration ratio of Yb3+ /Ho3+ was 6:1 and the concentration of Ho 3+ ion was 1.5 mol.%. The up-conversion mechanism was also studied. The green and red emission peaks were the two-photon absorption according to the relationship between the pump power and the luminescence intensity.     

Optical,thermal and luminescence properties of La2O3–Ga2O3–ZrO2 glasses co-doped with Tm3+/Yb3+ prepared by containerless technique

Bulk La₂O₃–Ga₂O₃–ZrO₂ (LGZ) glass and Tm³⁺/Yb³⁺ co-doped LGZ glasses were synthesized successfully using containerless technique. Raman spectra result reveals that the matrix sample possesses the low maximum phonon energy of ～642 cm^?1. The glasses show good compatibility between large Abbe numbers (>31) and high refractive indices (n_d > 1.93). Moreover, transmittance measurements reflect that the glasses have high infrared transmittance of ～81.9%, small OH^– absorption coefficient and long mid-infrared cut-off wavelengths (～7.5 μm). The surface morphology of host glass was characterized by scanning electron microscopy (SEM) micrograph and energy dispersive spectroscopy (EDS) tests reflect that the doped compositions are distributed into the matrix glass homogeneously. The results of thermal analysis show that the glasses have good thermal properties (T_g > 769 °C). Excited by 980 nm laser, an intense 1810 nm fluorescence is obtained originating from the transition: ³F₄ → ³H₆ of Tm³⁺ ion, accompanied by upconversion emission. It can be observed that 1810 nm fluorescence has the highest intensity at 1 mol% Yb₂O₃ and owns broad full width at half-maximum (>245 nm), the luminescence intensity of ³F₄ → ³H₆ transition increases with rising temperature from 300 to 550 K. Furthermore, the value of energy transfer efficiency shows that Yb³⁺ can transfer energy to Tm³⁺ effectively. By fitting the attenuation curves, the lifetimes of 1810 and 474 nm emission can be acquired.     

Energy transfer and cross-relaxation induced multicolor upconversion emissions in Er~(3+)/Tm~(3+)/Yb~(3+) doped double perovskite La_2ZnTiO_6 phosphors

Investigation on the bright and stable upconversion(UC) phosphors with multicolor emissions is fundamental and significant for the frontier applications of display and tempe rature probe.He re,dive rse emitting colors with blue,cyan and yellowish green,which are caused by the energy transfer and crossrelaxation processes,are obtained by altering Er~(3+),Tm~(3+)and Yb~(3+) concentrations in Er~(3+)singly,Er~(3+)-Tm~(3+)-Yb~(3+)co-and tri-doped double perovskite La_2 ZnTiO_6(LZT) phosphors synthesized by a simple solid-state reaction.In addition,excellent infrared emission at 801 nm located at "first biological windo w" is collected in Tm~(3+)-Yb~(3+)co-doped phosphors.Meanwhile,the temperature sensing properties based on the thermally coupled levels(~2 H_(11/2)/~4S_(3/2)) of Er~(3+) ions were analyzed from 298 to 573 K of LZT:0.15 Er~(3+)/0.10 Yb~(3+)phosphor,demonstrating that the maximal sensitivity value is about56×10-4 K~(1-) at 448 K.All these results imply that this kind of UC material has potential applications in display,bioimaging and optical device.     

Preparation and upconversion luminescence of monodisperse Gd2O3：Ho^3＋,Yb^3＋ nanocrystals

Gd2O3:Ho3+,Yb3+ nanocrystals were synthesized via solvothermal method.X-ray diffraction(XRD),transmission electron microscopy(TEM),absorption and upconversion spectra were employed to characterize the synthesized nanocrystals.The results of XRD and TEM showed that obtained Gd2O3:Ho3+,Yb3+ nanocrystals were cubic in crystal structure and uniform spherical in morphology.The average crystallite size was calculated to be 7.5 nm.Green and red up-conversion emissions corresponding to(5F4,5S2)→5I8 and 5F5 → 5I8 transition were observed upon 980 nm excitation at room temperature.The results indicated that both green and red luminescence were based on the two-photon processes.Laser power and doping concentration dependence of the upconverted emissions were studied to understand the upconversion mechanisms.Excited state absorption and energy-transfer processes were discussed as the possible mechanisms for the visible emissions.     

Gd3+ ion induced UV upconversion emission and temperature sensing in Tm3+/Yb3+:Y2O3 phosphor

Cubic phase Tm³⁺/Yb³⁺:Y₂O₃ and Tm³⁺/Yb³⁺/Gd³⁺:Y₂O₃ phosphors were prepared by low temperature combustion technique for upconversion emission in UV-visible range.The 980 nm excitation has generated UV emission at 314 nm in tridoped phosphor due to the energy transfer from Tm³⁺ to Gd³⁺ion.Characteristic emission bands from Tm³⁺ are also observed in both the phosphors....     

Size dependence of up-conversion luminescence of NaYF4:Yb3+/Tm3+

Tm³⁺/Yb³⁺ codoped NaYF₄ microcrystals were synthesized using a hydrothermal method. The bright upconversion light was observed under 980 nm excitation. The upconversion luminescence was systematically investigated at different Yb³⁺ concentrations and different reaction temperatures and time. The sample with 60% Yb³⁺ concentration and reacting at 180 °C for 24 h possessed the highest luminescent efficiency. The higher luminescent efficiency was contributed to a large surface area. The large surface area induced the large vibration mode by absorbed H₂O and CO₂. The larger vibration mode could enhance the energy transfer efficiency from the excited Yb³⁺ to Tm³⁺ by the process of phonon assisted energy transfer.     

Spectroscopic investigations on Yb~(3+) doped and Pr~(3+)/Yb~(3+) codoped tellurite glasses for photonic applications

In this work we repo rt on structural and spect roscopic properties of Yb3+doped and Pr~(3+)/Yb~(3+)co-doped TeO_2-Bi_2 O_3-ZnO-Li_2 O-Nb_2 O_5(TBZLN) tellurite glasses.Bending and stretching modes of TeO_2 and Te-OH bond(strong and weak) were analysed from the deconvolution of observed Raman and FT-IR spectra.Based on the absorption measurements,the energy bands of Yb~(3+)and Pr~(3+)ions are assigned.The spectroscopic properties for the radiative transitions of Yb~(3+)and Pr~(3+)ions were reported using McCumber and Judd-Ofelt theories.Visible emission bands originating from ~3 P_1 and ~3 P_0 to lower lying levels of Pr~(3+)were registered under 447 nm excitation.The emission band around 1334 nm assigned to the Pr~3:~1 G_4→~3 H_5 was observed when excited at 980 nm.The stimulated emission cross-section(σ_(emi)(λ))and effective linewidth(Δλ_(eff)) for the ~3 P_1→~3 H_6,~3 P_1→~3 H_5,~3 P_0→~3 H_6,~3 P_0→~3 F_2,~3 P_1→~3 F_3,~3 P_1→~3 F_4,~3 P_0→~3 F_4 and ~1 G_4→~3 H_5 transitions of Pr~(3+)are reported.Upconversion luminescence in Pr~(3+)/Yb~(3+)codoped glass upon 980 nm excitation was measured.Possible resonant transfer processes between Yb~(3+)and Pr~(3+)ions are presented and discussed.The chromaticity co-ordinates were also evaluated from the visible emission spectra showing that Pr~(3+)/Yb~(3+)co-doped glass may be suitable for the development of yellow-orange(λ_(exc)=447 nm) and near white light(λ_(exc)=980 nm) emitting devices in photonics.     

Spectral properties and energy transfer of Tm^3＋/Ho^3＋-codoped Ga2O3-Bi2O3-GeO2-PbO glasses

The 2.0 μm emission originating from Ho^3＋：^5I7→^5I8 were investigated upon excitation with 808 nm laser diode （LD） transition in Ho^3＋/Tm^3＋-codoped gallate-bismuth-germanium-lead glasses Energy transfer （ET） process between Tm^3＋： ^3F4 level and Ho^3＋： ^5I7 level was also discussed. It was noted that the measured peak wavelength and stimulated emission cross-section of Ho^3＋-doped bismuth-germanium-lead glasses were -2.02 μm and 5.1×10^-21 cm^2, respectively. Intense emission of Ho^3＋ in Tm^3＋/Ho^3＋-codoped GBPG glass were observed, which resulted from the ET between Tm^3＋： ^3F4 and Ho^3＋： ^5I7 level upon excitation with 808 nm LD.     

Fabrication and gain performance of Er^3＋/Yb^3＋-codoped tellurite glass fiber

Er^3＋/Yb^3＋-codoped TeO2-ZnO-BaO-La2O3 tellurite glass fiber was fabricated by rotation and rod-in-tube technologies. The thermal stability and optical refractive index of the core and cladding glasses were determined by DTA and optical coupler, respectively. The average background loss of tellurite glass fiber was 1.8 dB/m at 1310 nm. Optical microscopy and field emission scanning electron microscope （FESEM） were used to study structural characteristics of preforms and optical fibers. The main loss of tellurite glass fiber could be attributed to scatter centre due to core-cladding interface defects. The amplifier performance of tellurite glass fiber was investigated by pumping with 980 nm laser diode （LD）. The gain coefficient and maximum signal gain were 0.21 dB/mW and 10 dB, respectively, for a pumping power of 120 mW. Gains exceeding 5 dB were obtained over 30 nm bandwidth from 1535 to 1565 nm. The minimum noise figure was 4.8 dB at 1557 nm.     

Up-conversion luminescence of Er~（3＋）-doped and Yb~（3＋）/Er~（3＋） co-doped 12CaO·7Al_2O_3 poly-crystals

The optical properties of Er3+-doped and Yb3+/Er3+ co-doped 12CaO·7Al2O3 (C12A7) poly-crystals, synthesized by high temperature solid state method, were investigated in detail. For Er3+-doped and Yb3+/Er3+ co-doped C12A7 poly-crystals, two main emission bands centered around 530/550 nm (green) and 660 nm (red) were observed under 980 nm diode laser excitation via an up-conversion process. The intensity of green up-conversion emission had a strong increase in Er3+ (1.0 mol.%, 1.5 mol.%, 3.0 mol.%), and the intensity ratio of red to green up-conversion emission had an increase in Yb3+ (1.0 mol.%, 2.0 mol.%, 10. 0 mol.%)/Er3+ (fixed at 1.0 mol.%). This detailed study of the up-conversion processes allowed us to identify the dominant up-conversion mechanisms in Er3+-doped and Yb3+/Er3+ co-doped C12A7 poly-crystals.     

Structure,Upconversion and Fluorescence Properties of Er3+-Doped TeO2-TiO2-La2O3 Tellurite Glass

Tellurite glasses were generally applied in rare earth optical materials due to their excellent physical and chemical properties. In this study, novel tellurite glasses composed of TeO₂-TiO₂-La₂O₃ were prepared by conventional melting-quenching method. Some basic physical parameters such as density, refractive indices, transition temperature and crystalline temperature were measured. The structure was analyzed by Raman spectra. The absorption, upconversion and fluorescence spectra were measured by UV-Vis-NIR spectrophotometer and spectrofluorimeter. Under 980 nm laser excitation, upconversion luminescence centered at 531, 545 and 657 nm corresponding to the transition ⁴H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 respectively, were observed. The effects of TiO₂ concentration on structure and upconversion luminescence intensity were discussed. The result indicated that the upconversion intensity increased as the phonon concentration decreased. The fluorescence properties of Er³⁺ doped glass were also studied. The dominant peak centered at 1531 nm and full width at half maximum (FWHM) was 64 nm. The Er³⁺ stimulated emission cross-section was calculated on the basis of McCumber theory. The possible mechanism of upconvesion and fluorescence were proposed.     

Energy transfer and 2 μm emission in Tm~(3+)/Ho~(3+) co-doped(Y_(0.87)La_(0.1)Zr_(0.03))_2O_3 nanopowders

(Y_(0.87)La_(0.1)Zr_(0.03))_2O_3 nanopowders doped with various concentrations of Tm~(3+) and Ho~(3+) were prepared by the citrate method. The standard cubic Y_2O_3 phase can be matched in the Tm~(3+)/Ho~(3+) co-doped(Y_(0.87)La_(0.1)Zr_(0.03))_2 O_3 nanopowders. The nanopowders exhibit average particle sizes of 40,60, 80 and 100 nm after calcinated at 900,1000,1100 and 1200℃,respectively. The energy transfer from Tm~(3+) to Ho~(3+) and the optimum fluorescence emission around 2 μm were investigated. Results indicate that the emission bands at around 1.86 and 1.95 μm correspond to ~3 F_4→~3 H_6 transition of Tm~(3+) and ~5 I_7→~5 I_8 transition of Ho~(3+), respectively.Better spectral properties were achieved in Tm~(3+)/Ho~(3+) co-doped(Y_(0.87)La_(0.1)Zr_(0.03))_2O_3 nanopowders with the average size of 100 nm obtained at the conditions of the treatment of precursors calcinated at 1200 ℃ for 2 h doped with 1.5 mol% Tm~(3+) and 1 mol% Ho~(3+).     

Upconversion luminescence of Y2O3：Er^3＋ ,Yb^3＋ nanoparticles prepared by a homogeneous precipitation method

Y2O3： Er^3＋, Yb^3＋ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980 nm laser excitation. The results of XRD showed that the obtained Y2O3：Er^3＋,Yb^3＋ nanoparticles were of a cubic structure. The average crystallite sizes calculated were in the range of 28-40 nm. Green and red upconversion emission were observed, and attributed to ^2H11/2,^4S3/2→^4I15/2 and ^4F9/2→^4I15/2 transitions of the ion, respectively. The ratio of the intensity of green emission to that of red emission drastically changed with a change in the EDTA 2Na concentration. In the sample synthesized without EDTA, the relative intensity of the green emission was weaker than that of the red emission. The relative intensities of green emission increased with the increased amount of EDTA 2Na used. The possible upconversion luminescence mechanisms were discussed.     

Effect of BaF2 addition on luminescence properties of Er3+/Yb3+ co-doped phosphate glasses

Er~(3+)/Yb~(3+) co-doped phosphate glasses(P_2O_5-Al_2O_3-BaO-BaF_2-K_2O-Er_2O_3-Yb_2O_3) with varying BaF_2 content,were prepared by a conventional melt quenching technique and their spectroscopic properties were examined through the Raman, absorption, emission and decay measurements. Raman spectra(350-1400 cm~(-1)) of the Er~(3+)/Yb~(3+) co-doped phosphate glasses with varying BaF_2 content, were recorded upon laser excitation at 785 nm. Near infrared luminescence spectra were measured in the1400-1600 nm region under 970 nm diode laser excitation and characteristic band was observed at1533 nm corresponding to ~4Ⅰ_(13/2)→~4Ⅰ_(15/2) transition of Er~(3+) ion. The decay curves for the ~4Ⅰ_(13/2) level of Er~(3+)ion, were measured and the lifetime is found to decrease from 7.94 to 7.70 ms when BaF_2 content increases from 0 to 8 mol% and then increases up to 7.83 ms with further increase in BaF_2 content(12 mol%). The emission cross-section.lifetime and figure of merit for the ~4Ⅰ_(13/2)→~4Ⅰ_(15/2) transition of Er~(3+) ion were evaluated and compared to the other host matrices. The upconversion luminescence was measured and intense red emission was observed for all the studied samples.     

Preparation and luminescence properties of BaWO4：yb3＋/Tm3＋ nano-crystal

This research investigated the effect of different contents of Tm3+and different concentration ratios of Yb/Tm on the lumi-nescent properties of BaWO4:Yb3+/Tm3+nano-crystal synthesized by the hydrother...     

Preparation and Characterization Upconversion Luminescence Material of Yttrium Aluminate Doped with Rare Earth

Low phonon energy yttrium aluminate was adopted as matrix and the upconversion materials yttrium aluminate co-doped with Yb³⁺ and Er³⁺ was synthesized by solid-state reaction method. The X-ray diffraction spectra and the upconversion emission spectra of various samples were measured and the effect of Er³⁺ concentration, sensitization, fluxing agent and calcining temperature on the luminescence properties was studied. Research results showed that the sample could emit green light at 543 and 570 nm when excited 980 nm laser; the optimum concentration of Er³⁺ should be 1.0%; sensitization of Yb³⁺ could enhance luminescent effects of Er³⁺ obviously; the optimum content of F₃BO₃ fluxing agent should be 8% and the optimum calcining temperature should be 1500 °C.     

Down-and up-conversion processes in Nd3+/Yb3+ co-doped sodium calcium silicate glasses with concomitant Yb2+ assessment

Novel Nd³⁺/Yb³⁺ co-doped sodium calcium silicate glasses were prepared by melting quenching method:Spectroscopic study was carried out as a function of doping content by fixing sensitizer(Nd³⁺) concentration to 0.2 mol% and adjusting activator(Yb³⁺) from 0 to 1.0 mol%.The energy transfer(ET)mechanisms between Nd³⁺and Yb³⁺ are discussed based on their energy levels and excitation powerdependence emission intensity.Results show that...