Spectroscopic Properties of Er^3＋-Doped TeO2-WO3-ZnO-ZnF2 Glasses

The Er^3 -doped TeO2-WO3-ZnO-ZnF2(TWZOF) glasses were prepared. The absorption spectra, 1.5μm emission spectra and fluorescence lifetimes of Er^3 , excited at 970nm, were measured. The J-O parameters Ωt(t=2, 4, 6), absorption and emission cross-sections were calculated. The dependence of the 1.5μm emission intensity, fluorescence lifetime and bandwidth of the Er^3 emission upon the contents of ZnF2 in glass were investigated. In TWZOF glass, Er^3 ions had a broad emission profile around 1.5μm with the maximum FWHM of 83nm. With the increasing of the content of ZnF2, the emission intensity at peak wavelength and the fluorescence lifetime of Er^3 at 1.5μm increase.     

Optical Spectroscopy of Er^3＋ and Er^3＋/Yb^3＋ Co-doped Bi2O3-GeO2-B2O3-ZnO Glasses

The （60 - x）Bi2O3 - xGeO2-30B2O3-10ZnO （x = 5, 10, 20, 30 molar percent） glasses doped with Er^3＋ and Er^3＋/Yb^3＋ were fabricated using the melting method. The thermal stability of the glasses was studied with their DTA curves. The results show that the difference between the glass transition temperature and the crystallization onset temperature increases with the increase of GeO2 content, indicating that the thermal stability of the glass has become better. The absorption spectra were recorded and the stimulated emission cross sections were calculated using the McCumber theory. The Ω2, O4, and Ω6 parameters,the transition probability, the radiative lifetime, and the fluorescence branch ratio of Er^3＋ for optical transition were calculated from their absorption spectra in terms of reduced matrix U^（t）（λ = 2, 4, 6） character for optical transitions. The infrared emission of Er^3＋ was measured upon excitation with 970 nm light and the full width at half-maximum （FWHM） was estimated from the emission spectra. The pumping efficiency and the intensity of the emission at the 1.54 μm band of Er^3＋ were enhanced considerably by co-doping Yb^3＋ .     

Highly Er3+/Yb3+ Co-Doped Fluoroaluminate Glasses for Microchip Laser at 1.54 μm

A series of highly Er3 /Yb3 co-doped fluoroaluminate glasses were investigated in order to develop a microchip laser at 1.54 μm under 980 nm excitation. Measurements of absorption, emission and up-conversion spectra were performed to examine the effect of concentration quenching on spectroscopic properties. In the glasses with Er3 concentrations below 10% (mol fraction), concentration quenching is low and the Er3 /Yb3 co-doped fluoroaluminate glasses gave stronger fluorescence of 1.54 μm from the 4I13/2→ 4I15/2 transition than those of Er3 singly-doped glasses. In the glass with Er3 concentrations above 10%, concentration quenching of 1.54 μm obviously occurs more than that of the Er3 singly-doped samples because of the back energy-transfer from Er3 to Yb3 . To obtain the highest emission efficiency at 1.54 μm, the optimum in mol fraction when the Er3 concentration is less than 10%.     

Research on Up-Conversion Mechanism in Er3+/Yb3+-Codoped Oxyfluoride Glass

Er3 /Yb3 -codoped oxyfluoride crystallite glass was prepared with melting technique. The compositions and the melting temperature and the annealing temperature of the rare earth-doped crystallite glass were studied in detail. The emission spectra of samples were measured with the Hitachi F-4500 fluorescent photometer pumped by 980 nm wavelength laser. The up-conversion luminescence mechanism was illuminated on the view of the photophysics. By measuring the relationship between luminescent intensity and pump power, it is confirmed that the emission peaks at 550 nm belong to two-photon process, while that at 665 nm belongs to three-photon process. Moreover, the distributions of crystalline were determined by SEM.     

Investigation on Preparation and Fluorescence Properties of Oxy-Fluoride Glass Co-Doped with Er^3＋ and Yb^3＋

The glass sample based on the composition of 45PbF2-45GeO2-10WO3 co-doped with Yb^3 /Er^3 was prepared by the fusion method in two steps : melted at 950℃ for 20～25min then annealed at 380℃ for 4 h. Through the V-prism it is found that the refractive index of host glass and the sample are 1.517 and 1.65 respectively. The transmittance was observed by using the ultraviolet-visible-infrared spectrometer in the wavelength range from 0.35 to 2.5μm. The transmittance of the host glass is beyond 73%. That of the sample is beyond 50% and there are characteristic absorption peaks of rare-earth ions. The emission spectrum was measured by using the Hitachi F-4500 fluorescent spectrometer pumped by 980nm semiconductor laser. There are a strong emission peak at 530 nm and a weak peak at 650 nm.     

Broadband 1.53 μm emission in Er3+-doped Ga-Bi-Pb-Ge heavy metal oxide glasses

We investigated the thermal stability and spectroscopic properties of the 1.53 μm emission from 4I13/2→4I15/2 transition of Er3+ ions in Er3+/Yb3+-codoped Ga-Bi-Pb-Ge heavy metal oxide glass for use in broadband fiber amplifiers. It was noted that the addition of GeO2 ef-fectively enhanced the thermal stability of the heavy metal oxide glass studied. The emission peak located at approximately 1530 nm with a full width at half-maximum of approximately 58 nm. The measured lifetime and the calculated emission cross-section of this transition were ～3.2 ms and-10.3×10-21 cm2, respectively. As a result, Ga-Bi-Pb-Ge heavy metal oxide glasses were assumed to be potential host material for the 1.53 μm broadband optical fiber amplifiers.     

Preparation and Characterization of Er2O3 Nanocrystals by Schiff Base Salt Combustion Method

The nanocrystals Er2O3 were prepared by using a combustion method with Schiff base as a chelating agent. The Er(Ⅲ) coordanation compound of Schiff base, obtained from erbium nitrate and retinal Schiff base, underwent a combustion process and voluminous ashes formed when calcimining the complex in air. Pure cubic Er2O3 nanocrystals with a diameter of 13nm were produced. The nanocrystals were homogeneous and rigid coacervation was not observed. The photoluminescence emission spectrum of the erbium (Ⅲ) oxide nanocrystals shows that it has a characteristic peak at 1.54μm, and some other shoulder peaks appear on both sides of the main peak.     

Influence of B2O3 on Spectroscopic Properties of Er^3＋/Yb^3＋ Co-Doped Tungsten-Tellurite Glasses

A series of novel Er^3＋/Yb^3＋ co-doped （85- x ） TeO2-15WO3-xB2O3 （TWB;x=2%,5%,8%（mole fraction） ） glasses were prepared. Influence of B203 on the spectroscopic properties of Er^3＋/Yb^3＋ co-doped tungsten-tellurite glasses were investigated. It is found that the intensity of 1.5μm fluorescence, lifetime of the ^4I13/2 level and upconversion fluorescence all decrease with the increase of B2O3 content. The product of full width at half maximum （FWHM） and stimulated emission cross-section （σe^peak） of Er^3＋ ：^4I13/2→^4I15/2 transition has an optimum when B203 is 5% （mole fraction）. The emission spectra of Er^3＋ ： ^4I13/2→^4I15/2 transition was analyzed using peak-fit routine, and an equivalent four-level system was proposed to estimate the stark splitting for the 411512 and ^4I13/2 levels of Er^3＋ ions in TWB glasses at room temperature.     

Study on vacuum ultraviolet spectra of amorphous Er_2O_3 films on Si（001） substrates

Amorphous Er2O3 films have been fabricated on p-type Si(001) substrates using radio frequency magnetron sputtering technique. Vacuum ultraviolet spectra were employed to investigate the samples. An optical gap of 6.17 eV for Er2O3 films was obtained from the ab-sorption coefficient spectra. A possible reason was put forward to explain the inconsistent results about the band gap of Er2O3 in literatures. Emission spectra exhibited a strong emission band at 494 nm with the incident ultraviolet light of 249 nm. The observed high density of emission bands of Er2O3 films in the visible wavelength indicated that Er2O3 films could be used in Si solar cells for increasing conversion efficiency.     

Effect of alkali metal oxides R2O （R=Na, K） on 1.53 μm luminescence of Er3＋-doped Ga2O3-GeO2 glasses for optical amplification

This paper reported the thermal stability and spectroscopic properties of Ga2O3-GeO2-Na2O-K2O (GGNK) glasses doped with Er3+. The GGNK glasses were characterized by differential scanning calorimetry (D...     

A novel green-yellow emitting phosphor Ca1.5Y1.5Al3.5S1.5O12：Ce^3＋ and its luminescence properties

We described the synthesis and luminescence of Ca1.5Y1.5Al3.5Si1.5O12:Ce3+ phosphor for light emitting diode (LED). The crystal-linity, morphology, structure, and luminescence spectra were examined by X-ray diffraction, field emission-scanning electron microscopy and photoluminescence spectroscopy. The results showed that Ca1.5Y1.5Al3.5Si1.5O12:Ce3+ phase was a dominating phase with little impurity phase peaks of Y2O3 when the sintered temperature reached to 1400 oC. Field emission scanning electron microscopy (FE-SEM) images showed the particle size of the phosphor was about 3 μm. Meanwhile, the excitation and emission spectra indicated that the as-prepared phosphors could be effectively excited by blue (460 nm) light and the excitation spectrum showed a broad band extending from 400-500 nm, while emission spectrum showed a broad yellow band peaking at 534 nm. The decay curve at the emission peak consisted of fast and slow components. The Ca1.5Y1.5Al3.5Si1.5O12:Ce3+ should be a promising yellow phosphor for near blue-based white-light-emitting diodes (LEDs).     

Photoluminescence properties of M2ZnSi2O7:Eu2+（M=Sr,Ba）

The hardystonite phosphors of Eu2+ activated M2ZnSi2O7(M=Sr,Ba) were synthesized by combustion-assisted method.They were systematically characterized by photoluminescence excitation and emission spectra.The emission spectra of these two phosphors showed that the main emission peaks are at 475 and 503 nm due to 4f65d1→4f7 transition of Eu2+.Both phosphors could be efficiently excited in the wavelength range of 250-425 nm where the near ultraviolet light-emitting diode was well matched.The(x,y) color coordinates were determined with the emission values(x,y)=(0.41,0.21) and(0.16,0.45) for the M2ZnSi2O7:Eu2+(M=Sr,Ba) phosphors.     

Upconversion luminescence of Y2O3:Er3+, Yb3+ nanoparticles prepared by a homogeneous precipitation method

Y2O3: Er3 , Yb3 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:Er3 ,Yb3 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 Er3 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.     

A blue luminescence glass-ceramics of Eu^2＋ ions activated Li2O-BaO-B2O3

New blue luminescence glass-ceramic samples were prepared in air by annealing of the Eu^3＋-doped Li2O-BaO-B2O3 glass. The as-made glass samples only showed the sharp emission peaks assigned to the transitions of 5^D0-7^Fj （J=0, 1, 2, 3, 4） of Eu^3＋ ions. The glass-ceramic samples gave a strong and broad emission band peaking at about 382 nm ascribed to the 5d-4f transition of Eu^2＋ ions. The optical properties such as excitation and emission spectra, and the decay time of the Eu^2＋ ions were investigated in the glasses or the glass-ceramics samples. The X-ray diffraction pattern showed that LiBan9O15 might be demonstrated to be the crystallites in the glass-ceramic, which contributed to the blue luminescence. SEM micrograph was investigated on the glass-ceramic samples obtained by crystallization of the glass matrix resulting in a mixture of poly-crystals.     

Enhancement of 1.54 μm emission in Er：LiNbO_3 crystal by codoping with Zn~（2＋） ions

The enhanced intensity and lengthened lifetime of 1.54 μm emission were observed for Er:LiNbO3 crystal codoped with Zn2+ ions.The ZnO codoping led to the reduction of the green upconversion emission in Er:LiNbO3 crystals.The decay trace of the 4S3/2→4I15/2 was ob-viously nonexponential for Er:LiNbO3 codoped with 0 and 3 mol.% ZnO,but became exponential for one codoped with 6 mol.% ZnO.The OH-absorption spectra showed after codoping with Zn2+ ions,the OH-absorption peaking position shifted from ~3495 to 3484 cm-1,and the absorption cross section decreased.These spectroscopic characteristics suggested that the improvement of 1.54 μm emission was attributed to the reduction of Er3+ cluster sites.     

Local microstructure and photoluminescence of Er-doped 12CaO·7Al2O3 powder

Er-doped 12CaO·7Al2O3 (C12A7:Er) powders were prepared using the sol-gel method followed by annealing inorganic precursors. X-ray diffraction (XRD), Raman and absorption spectra revealed that Er ions existed and substituted Ca2 lattice site in C12A7. The photoluminescence of C12A7:Er at room temperature was observed in the visible and infrared region using 488 nm (2.54 eV) Ar line as excitation source, respectively. The sharp and intense green emission bands with multi-peaks around 520 nm and 550 nm correspond to the transitions from the excited states 2H11/2 and 4S3/2 to the ground state 4I15/2, respectively. Furthermore, red emission band around 650 nm was also observed. It was attributed to the electronic transition from excited states 4F9/2 to the ground state 4I15/2 inside 4f-shell of Er3 ions. The intensive infrared emission at 1.54μm was attributed to the transition from the first excited states of 4I13/2 to the ground state (4I15/2). The temperature dependent photoluminescence of infrared emission showed that the integrated intensity reached a maximum value at near room temperature. The forbidden transitions of intra-4f shell electrons in free Er3 ions were allowed in C12A7 owing to lack of the inversion symmetry in the Er3 position in C12A7 crystal field. Our results suggested that C12A7:Er was a candidate for applications in Er-doped laser materials, and full color display.     

Fabrication and Luminescence Properties of Ca2Gd8(SiO4)6O2:Er3+ Phosphors via Sol-Gel Process

Ca2RE8(SiO4)6O2 (RE=Y, Gd, La) is a kind of ternary rare-earth-metal silicate with the oxyapatite structure, which was used as host materials for the luminescence of various rare earth and mercury-like ions. Ca2Gd8(SiO4)6O2:Er3 phosphors were prepared through the sol-gel process. X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicate that the phosphors crystallized completely at 1000 ℃. SEM study reveals that the average grain size is 400～1000 nm. In Ca2Gd8(SiO4)6O2:Er3 phosphors, the Er3 shows its characteristic green emission at 528 nm (2H11/2-4I15/2) and 548 nm(4S3/2-4I15/2) upon excitation into 382 nm, with an optimum doping concentration of 5% (mole fraction) of Gd3 in the host lattices.     

Sol-gel processed Ce^3＋, Tb^3＋ codoped white emitting phosphors in Sr2Al2SiO7

Sr2Al2SiO7：Ce^3＋, Tb^3＋ white emitting phosphors were fabricated using the sol-gel method. X-Ray Powder Diffraction （XRD） analysis confirmed the formation of Sr2Al2SiO7：Ce^3＋, Tb^3＋. Scanning Electron Microscopy （SEM） observation indicated that the microstructure of the phosphor consisted of regular fine grains with an average size of about 0.5-1 μm. Luminescence properties were analyzed by measuring the photoluminescence spectra. The Ce^3＋, Tb^3＋-codoped Sr2Al2SiO7 phosphors showed four main emission peaks： one at 414 nm for Ce^3＋ and three at 482, 543, and 588 nm for Tb^3＋. The emission spectra of the samples with different doping concentrations showed that the Tb^3＋ emission was dominant because of the persistent energy transfer from Ce^3＋. The decay characteristic was better than that prepared by the solid-state process in the comparable condition. The codoped phosphor displayed long persistent white phosphorescence.     

Shape-Controlled Synthesis and Upconversion Luminescence of Y2O3:Yb, Er Microstructures

The Y2O3: Yb3 , Er3 microstructures were fabricated by a hydrothermal method without surfactants.The microstructures structure was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM,KYKY 1000B).The up-conversion luminescence spectra were studied under 978 nm laser diode excitation.In Yb3 and Er3 codoped Y2 O3 microcrystals, the relative intensity of green emission became stronger as the morphology of sample changed from wires to films.     

Fabrication and gain performance of Er3+/Yb3+-codoped tellurite glass fiber

Er3+/Yb3+-codoped TeO2-ZnO-BaO-La2O3 tellurite glass fiber was fabricated by rotation and rod-in-tube technologies. The ther-mal stability and optical refractive index of the core and cladding glasses were determined by DTA and optical coupler, respectively. The av-erage 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 um bandwidth from 1535 to 1565 nm. The minimum noise figure was 4.8 dB at 1557 um.