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＋ .     

Spectral Properties and Upconversion Luminescence of Er^3＋, yb^3＋： BaWO4 Crystal

The optical quality of Er^3＋, yb^3＋： BaWO4 crystal was gown by Czochralski method. Absorption spectra were measured and energy levels were assigned. According to Judd-Ofelt theory, the spectral strength parameters of Er^3＋ ion were fitted to beΩ2 =0.3926 x 10^-20 cm^2, Ω4 =0.0721×10^-20 cm^2, Ω6 =0.0028 ×10.20 cm^2. Emission peaks centered at around 523,544 and 670 nm were observed under 334 nm He-Cd laser excitation and emission peaks centered at 1001 and 1534 nm were detected under 976 nm laser excitation. Strong green emission was also observed when the crystal was pumped with 808 nm and 976 nm laser. The mechanisms of frequency upconversion and sensitization were analyzed.     

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.     

Spectroscopic Properties and Effect of Radiation Trapping of a New Er^3＋/Yb^3＋ Co-Doped Tellurite-Silicate Glasses

A new serials of Er^3＋/Yb^3＋ co-doped tellurite-silicate glasses were prepared by the technique of high-temperature mehing. The thermal stability, absorption spectra, emission spectra and upconversion spectra were measured and investigated. It is found that these kinds of glasses have good thermal stability, broad FWHM and large stimulated emission cross-section. The three upconversion emission at 525, 546, 658 nm, corresponding to the ^2H11/2→^4Ⅰ15/2, ^4S3/2→4^Ⅰ15/2 and ^F9/2→^4Ⅰ15/2 transitions of Dr^3＋ ions,     

Co-Precipitation Synthesis and Spectral Characteristics of Long Afterglow Phosphor Y2O2 S： Sm^3＋, Mg^2＋ , Ti^4＋

Y2O2S：Sm^3＋, Mg^2＋, Ti^4＋ phosphor was synthesized by co-precipitation method. The crystalline structure of all synthesized phosphors was investigated by XRD. The result showed that all synthesized phosphors had a hexagonal crystal structure, which was the same as Y2O2S. The emission spectrum and excitation spectrum were measured, and the effect of Sm^3 ＋ molar ratio on the spectra was discussed. The emission spectra of the phosphors showed three emission peaks due to typical transitions of Sm^3 ＋ （4G5/2→6HJ ,J = 5/2, 7/2, 9/2）, and the emission peaks at 606 nm was stronger than others. With the increase of Sm^3 ＋ molar ratio, the emission intensity was strengthened. The excitation peaks were ascribed to the representative energy transition 4f→4f of Ti^4＋ phosphor prepared by co-precipitation method was Sm^3＋ ions. The results indicated that the Y2O2S ： Sm^3＋ , Mg^2＋ , an efficient long afterglow phosphor.     

Study on Growth and Spectra Properties of Nd: GGG Crystal

The laser crystal Nd GGG was grown by Cz method. The optimum processing parameter is that the pulling rate is 2~4mm·h-1, the rotation rate is 20~40 r·min-1 and the cooling rate is 20℃. The absorption and fluorescence spectra of Nd GGG were measured. The main absorption peak of Nd GGG is at 808 nm and the fluorescence emission peak is at 9430cm-1, corresponding to 4F3/2-4I11/2 emission band of Nd3 ions.     

Spectroscopic properties of ytterbium doped KLu（WO_4）_2

Monoclinic Yb3+-doped KLu(WO4)2 (Yb:KLuW) crystal with large sizes was grown by top-seeded solution growth (TSSG) method. Room-temperature absorption and fluorescence spectra were measured. The ground-state energy-level splitting was 562 cm-1. The absorption cross section, peak emission cross section as well as the minimum inversion fraction ?min and the minimum absorbed pump intensity Imin were calculated. The measured emission lifetime was 0.676 ms and the emission spectral bandwidth (FWHM) was up to 55 nm. In comparison with established laser crystals the results suggested that this crystal has potential application in efficient tunable and femtosecond laser operation.     

Effect of mixing process on the luminescent properties of SrAl_2O_4:Eu~(2+),Dy~(3+) long afterglow phosphors

A new mixing method was developed for solid-state reaction synthesis of SrAl2O4:Eu2+,Dy3+ long afterglow phosphors.The morphology and crystal structure of the phosphors were analyzed with scanning electron microscope(SEM) and X-ray diffractometer(XRD).The excitation and emission spectra of the long afterglow phosphors were measured,and the main emission band was around 514 nm.The decay time of the product was measured and compared with the phosphors prepared using dry-mixing method and wet-mixing method.It ...     

Optical and thermoluminescence properties of Lu2Si2O7：Pr single crystal

Single crystal of Lu2Si2O7:Pr was grown by Czochralski method. Transmittance, photoluminescence excitation (PLE) and photo-luminescence (PL) spectra, X-ray excited luminescence (XEL) and fluorescence decay time spectra of the sample were measured and discussed to investigate its optical characteristics. The crystal structure of the as grown Lu2Si2O7:Pr was confirmed to be C2/m. There was a broad absorption peaking at 245 nm in the region from 200-260 nm. The PL spectrum was dominated by fast 3PJ→3HJ band peaking at 524 nm. The XEL spectrum was dominated by the fast 5d14f1→4f2 emission peaking at 265 nm. The 2D (temperature-intensity) and 3D (temperature-wavelength-intensity) thermally stimulated luminescence (TSL) spectra were measured. The Pr3+ ion was found to be the recombination center during the TSL process. Three obvious traps were detected in LPS:Pr single crystal with energy depth at 1.06, 0.78 and 0.67 eV.     

Luminescence Properties of Tb^3＋ -Doped LuAG Films Prepared by Pechini Sol-Gel Method

Lu3Al5O12（LuAG） thin films with different Tb^3＋ concentration were prepared on carefully cleaned （111 ） silicon wafer by a Peehini process and dip-coating technique. Heat treatment was performed in the temperature range from 800 to 1100 ℃. The crystal structure was analyzed by XRD. The results show that LuAG film starts to crystallize at about 900 ℃, and the particle size increases with the sintering temperature. Excitation and emission spectra of Tb^3＋ doped LuAG films were measured. The effects of heat-treatment temperature and doping concentration of Th3 ＋ on the luminescent properties were also investigated. For a comparison study, Th^3＋-doped LuAG powders were also prepared by the same sol-gel method.     

Syntheses and Characterization of Binuclear Complexes Tb（1-x）Eux（TTA）3 Phen

Rare earth ternary complexes Tb1-xEux（TTA）3Phen（x=0,0.25,0.5,0.75,1.0）were synthesized and characterized by DTA-TG,XRD and infrared（IR）.The photophysical properties of these complexes were studied in detail using ultraviolet absorption spectra and fluorescent spectra.Ultraviolet absorption showed that the energy absorption of the complexes mostly came from ligands.Infrared spectra of Tb1-xEux（TTA）3Phen complexes were similar to the pure complexes.TG curves proved that the complexes were stable.Tb3＋ emission was almost quenched and the Eu3＋ emission was enhanced by codoping the complexes.The Tb3＋ ion acted as an energy transfer bridge that helped energy transfer from poly（N-vinylcar-bazole（PVK）to Eu3＋.In addition,their PL and EL properties were systematically studied.     

Spectral properties of Tm,Ho:LiYF4 laser crystal

The LiYF4 single crystal codoped with thulium and holmium ions was successfully grown by the Cz method. The optimal technical parameters obtained were as follows: the pulling rate was 0.16 mm/h; the rotation speed was 3 rpm; the cooling rate was 15 °C/h. The result of XRD curve showed that as-grown Tm,Ho:LiYF4 laser crystal belonged to the monoclinic system with scheelite-type structure and space group I41/a. The cell parameters calculated were: a=0.52160 nm, c=1.09841 nm and Z=4. Absorption and fluorescence spectra of Tm,Ho:LiYF4 laser crystal at room temperature were measured and analysed. The absorption cross section, FWHM and absorption coefficient at 779.3 nm calculated were 7.44×10-21 cm2, 8.7 nm and 2.23 cm-1, respectively. An intensive fluorescence emission peak appeared near 2045 nm. The emission cross section and fluorescence lifetime were 0.87×10-20 cm2 and 10.8 ms, respectively. The ratio of Tm-Ho transfer to its back-transfer process was 10.6.     

Growth and optical properties of Pr~(3+):La_2CaB_(10)O_(19) crystal

Pr3+ doped La2CaB10O19 crystal were grown by the top-seeded solution growth(TSSG) method.The absorption spectra,emission spectra and lifetime were measured at room temperature.The J-O parameters(Ωt,t=2,4,6),the radiative transition probabilities AJ,J',oscillator strengths PJ,J',radiative lifetime τ,fluorescence branch ratios βJ and the value of integrated emission cross section have also been calculated.Five main absorption bands,3H4 to 3P1+3P2,3P0,1D2,3F3 + 3F4 and 3F2,were observed in the absorption spect...     

Crystal growth,structure and laser performance of a new Yb~(3+):KBaY(MoO_4)_3 crystal

A Yb~(3+):KBaY(MoO_4)_3(Yb3+:KBYM) crystal with dimensions of 51 mm × 27 mm x 10 mm was successfully grown by the TSSG method.The characteristics of the crystal structure and probability of good optical properties were analyzed.The absorption and emission spectra of Yb3+:KBYM crystal exhibit broadened bands,with the maximum absorption cross-sections of 1.17 x 10~(-20),1.44 ×10~(-20) and 1.37 x 10-20 cm~2 at976 nm for X-,Y-and Z-polarizations,respectively.The corresponding absorption FWHMs are as wide as 77,46 and 55 nm.The well-known re-absorption effect of Yb3+in the crystal is discussed.Two methods,the Fiichtbauer-Ladenburg method(FL) and reciprocity method(RM) were adopted to compute the emission cross-sections and results show a certain discrepancy but the errors are allowable.The laser potentiality of the Yb3+:KBYM crystal was also evaluated by calculations of minimum inversion fraction β_(min),saturation pump intensity I_(sat),the minimum pump intensity I_(min) and gain cross-sections spectra.Laser experiment was carried out and Watt-level continuous wave laser has been realized.Results indicate that the Yb~(3+):KBYM crystal with a disordered structure may be a potential laser media that can be used to generate tunable and ultrashort pulse laser emissions with high quality beam.     

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.     

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

Er-doped 12Ca0.7Al2O3 （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 Ca^2＋ 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 Er^3＋ ions. The intensive infrared emission at 1.54 μm was attributed to the transition from the fast 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 Er^3＋ ions were allowed in C12A7 owing to lack of the inversion symmetry in the Er^3＋ 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.     

Role of monovalent co-dopants on the PL emission properties of YAI3（BO3）4：Ce3＋ phosphor

The cerium （Ce3＋） doped yttrium aluminium borate （YAB） phosphor was synthesized by modified solid state reaction. The phosphor＇s phase purity and its emission properties were studied using powder X-ray diffraction pattern and photoluminescence spectroscopy. The synthesized YAB had rhomobohedral crystal structure. The phosphor had two different excitation and emission spectra. By 325 nm excitation, the phosphor had emission at 373 nm and with 363 nm excitation; the phosphor gave violet-blue emission at 418 nm. The UV emission of the phosphor originated due to Ce3＋ ions at the yttrium site and violet-blue emission owing to Ce3＋ ions at non-regular sites viz., A13＋ and interstitial sites. The emission intensity of the phosphor was enhanced when monovalent ions （K＋, Na＋, and F） were added as co-dopants. The crucial role of ionic radii of monovalent co-dopants on the emission enhancement of the YAB：Ce3＋ phosphor was reported. Thermogravimetric study showed that the YAB possessed high thermal stability at up to 900 ℃.     

Spectroscopic Properties and Judd-Ofelt Theory Analysis of Er^3＋-Doped Heavy Metal Oxyfluoride Silicate Glass

Er^3 -doped heavy metal oxyfluoride silicate glass was fabricated and characterized, and the absorption spectrum and fluorescence spectrum of the glass were studied. The Judd-Ofelt intensity parameters Ωt(t=2, 4, 6), spontaneous transition probability, fluorescence branching ratio and radiative lifetime of each energy levels for Er^3 were calculated by Judd-Ofelt theory, and stimulated emission cross-section of ^4I13/2→^4I15/2 transition was calculated by McCumber theory. The results show that fluorescence full width at half maximum and stimulated emission cross-section of Er^3 -doped heavy metal oxyfluoride silicate glass are broad and large, respectively. Compared with other host glasses, the gain bandwidth property of Er^3 -doped heavy metal oxyfluoride silicate glass is close to those of tellurite and bismuth glasses, and has advantage over those of silicate, phosphate and germante glasses.     

Kinetics of Fluorescence Decay in Er^3＋ ：YAG under 408.6 nm Excitation

The violet and green fluorescence spectra and the kinetics of fluorescence decay in Er^3＋ ：YAG crystal under 408.6 nm excitation were investigated by the time-resolved laser-induced fluorescence technique. The influence of multiphonon and energy transfer on the fluorescence decay of the ^4S3/2 rnultiplet were theoretically analyzed. A good agreement of the measured and the simulated decay curves was achieved. The continuous profile variety of the decay curves in the region from 548 to 561.2 nrn is found and it originates from the fluorescence overlap of ^2G9/2 and ^4S3/2 and the intensity ratio dominates the profile.     

Spectroscopic and fluorescence properties of Sm~(3+)-doped zincfluorophosphate glasses

Optical absorption and fluorescence spectra of Sm3＋-doped zincfluorophosphate glasses with molar composition of 44P2O5＋17K20＋9Al2O3＋（30-χ）ZnF2＋χSm2O3 （χ=0.01 mol.%, 0.05 mol.%, 0.1 mol.%, 0.5 mol.%, 1.0 mol.%, 2.0 and 3.0 mol.%） referred as PKAZFSm were prepared by melt quenching technique and were characterized through Raman, absorption, emission and decay curve analysis. From the absorption spectra, Judd-Ofelt intensity parameters were determined and were used to predict radiative properties such as transition probabilities （AR, radiative lifetimes （τR）, branching ratios （βR）, effective bandwidths （△λeff） and stimulated emission cross-section （σ（λp）） for the excited 4G5/2 luminescent level. The decay curve for the 4G5/2 level was single exponential for lower concentration and became non-exponential for higher concentrations. The non-exponential nature of the decay curves of the 4G5/2 level increased with increase in Sm3＋ ions concentration accompanied by decrease in lifetime due to energy transfer processes among the Sm3＋ ions. The non-exponential decay curves was well fitted to the generalized Inokuti-Hirayama model for S=6, indicating that the energy transfer among optically active ions was of dipole-dipole interaction. The cross-relaxation mechanism responsible for the quenching of lifetimes and the effect of variation of concentration on the spectroscopic properties were also discussed.