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＋ .     

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.     

Tm^3＋-doped tellurite glass with Yb^3＋ energy sensitized for broadband amplifier at 1400-1700 nm bands

A kind of novel experiment was disclosed as it possessed two bands of fluorescence emission at 1.4 and 1.6 μm, which were perfectly complimentary to the current C band of optic communication. The fluorescence was based on energy transfer and up-conversion processes between Tm^3＋ and Yb^3＋ under direct pumping of 975 nm LD. The spectra and lifetimes of Tm^3＋ fluorescence in the tellurite glass were described. The corresponding fluorescence characteristics and energy migration process were analyzed by the method of lifetime and intensity comparison. The mechanism of the up-conversion based IR fluorescence was presented upon analyzing the multi-photon pumping process. The potential advantages of Tm^3＋/Yb^3＋ co-doped tellurite glass as amplifier material were concluded.     

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.     

Highly Er^3 ＋／Yb^3＋ Co-Doped Fluoroaluminate Glasses for Microchip Laser at 1.54μm

A series of highly Er^3 /Yb^3 co-doped fluoroaluminate glasses were investigated in order to develop a microchip laser at 1.54μm under 980nm 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 Er^3 concentrations below 10% (mol fraction), concentration quenching is low and the Er^3 /Yb^3 co-doped fluoroaluminate glasses gave stronger fluorescence of 1.54μm from the 4113/2→^4I15/2 transition than those of Er^3 singly-doped glasses. In the glass with Er^3 concentrations above 10%, concentration quenching of 1.54μm obviously occurs more than that of the Er^3 singly-doped samples because of the back energy-transfer from Er^3 to Yb^3 . To obtain the highest emission efficien-cy at 1.54μm, the optimum doping-concentration ratio of Er^3 /Yb^3 is found to be approximately 1 : 1 in mol fraction when the Er^3 concentration is less than 10%.     

Growth and Spectral Properties of Crystal Er^3＋ ：Y0.5Gd0.5VO4

Er^3＋ ：Y0.5Gd0.5VO4 crystal with good optical quality was grown by Czochraski method. The structure of the crystal was determined by X-ray powder diffraction method. The segregation coefficient of Er^3 ＋ ions in the crystal was measured by the ICP method. The absorption and emission spectra were also measured. On the basis of the spectra, the absorption cross-sections, emission spectrum FWHM and fluorescence lifetime of the crystal were calculated. From the properties mentioned above.     

Tm~(3 )-doped tellurite glass with Yb~(3 ) energy sensitized for broadband amplifier at 1400–1700 nm bands

A kind of novel experiment was disclosed as it possessed two bands of fluorescence emission at 1.4 and 1.6 μm, which were per-fectly complimentary to the current C band of optic communication. The fluorescence was based on energy transfer and up-conversion proc-esses between Tm3 and Yb3 under direct pumping of 975 nm LD. The spectra and lifetimes of Tm3 fluorescence in the tellurite glass were described. The corresponding fluorescence characteristics and energy migration process were analyzed by the method of lifetime and inten-sity comparison. The mechanism of the up-conversion based IR fluorescence was presented upon analyzing the multi-photon pumping proc-ess. The potential advantages of Tm3 /Yb3 co-doped tellurite glass as amplifier material were concluded.     

2 μm mid-infrared optical spectra of Tm3+-doped germanium gallate glasses

Glasses with the composition of 65GeO212Ga2O3-10BaO-8Li2O-5La2O3(molar ratio) doped with 1.526 wt.%, 3.006 wt.%, 5.836 wt.%, 11.028 wt.%, and 15.678 wt.% Tm2O3, respectively, were fabricated by conventional melting method. According to the absorption spectra and the Judd-Ofelt theory, the J-O strength parameters (Ω2,Ω4, Ω6) were calculated, with which the radiative transition probabilities,branching ratios and radiative lifetimes were obtained. The infrared emission spectra (with 808 nm LD excitation) at～1.47 and～1.8 μm of various concentrations of Tm3+-doped glasses were studied. The emission intensity at～1.8 μm reached to the maximum when the Tm2O3-doping concentration was near to be～3.006 wt.% (1.0 mol.%), and then decreased as doping concentration increased further. The mechanism of the fluorescence intensity change was explained with the cross-relaxation effect and the concentration quenching effect of Tm3+. Meanwhile, according to McCumber theory, the absorption and emission cross-sections corresponding to the 3F4→3H6 transitions of Tm3+ at 1.8 μm was obtained. For Tm3+-doped germanate glasses, the maximum emission cross-section reached a value higher than that re-ported for fluorozircoaluminate glasses. It is expected to be a favorable candidate host for～2.0 μm mid-inflated laser because the glass shows favorable optical spectra.     

Structural and optical studies of Yb^3＋, Er^3＋ and Er^3＋/Yb^3＋ co-doped phosphate glasses

Phosphate glass samples with various Yb2O3 and Er2O3 contents were synthesized by the conventional melt quenching technique and characterized by X-ray diffraction,IR absorption spectroscopy and Raman scattering spectroscopy.The absorption,emission spectra and fluorescence decay studies were carried out both at low and room temperatures.Results showed the existence of several sites occupied by the rare earth ions in the phosphate glass.Up-conversion and cooperative fluorescence were also discussed.     

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...     

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%.     

Luminescence of Er3+ Doped Titanium Barium Glass Microsphere under 514 nm Excitation

The titanium barium glass microspheres doped with Er2O3 were designed and prepared. The components of the glass sample were 25TiO2-27BaCO3-8Ba(NO3)2-5ZnO2-10CaCO3-5H3BO3-10SiO2-7water glass-3Er2O3 (%, mass fraction). The emission spectra of titanium barium glass matrix and the titanium barium glass microsphere under 514 nm excitation were measured with micro-Raman spectrometer. Whispering gallery modes in the emission spectra from a 31 μm glass microsphere were observed. Many regularly spaced, sharp peaks appeared in the emission spectra of the Er2O3-doped glass microsphere. The wavelength separation between the two adjacent peaks is 1.92 nm for the 31 μm microsphere. According to the Lorenz-Mie formula, the calculated value of the wavelength separation between the two adjacent peaks is 1.95 nm. The observed resonances could be assigned by using the well-known Lorenz-Mie formula.     

Polarized spectral analysis of Er3+ ions in Er3+/yb3+:LiLa(MoO4)2 crystal

Optical characteristics and upconversion dynamics of Er3+ in Er3+/Yb3+:LiLa(MoO4)2 crystals were investigated. The absorption spectra, fluorescence spectra and the fluorescence decay curves were analyzed at room temperature. The infrared emission at 1538 nm and visible emissions at 520–569 and 640–670 nm, corresponding to 2H11/2,4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+ ions, were simultaneously observed in Er3+/Yb3+:LiLa(MoO4)2 crystals under 976 nm excitation at room temperature. The maximal emission cross-section near 1530 nm for π-polarization was 0.63×10–20 cm2 and the measured lifetime of 4I13/2 was 4.88 ms. The upconversion process was involved in sequential two-phonon processes, either the energy transfer from Yb3+ ions or by the excited state absorption.     

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.     

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.     

3.1 μm mid-infrared luminescence in Er3+ doped ZnF2 modified aluminum fluoride glass

Herein, melt-quenching and Er³⁺ doping were used to synthesize fluoride glass specimens with low phonon energies (582 cm⁻¹). These glass specimens exhibit intense 3.1 μm mid-infrared band emission when they are excited by a 980 nm laser diode, achieving a full width at half maximum (FWHM) of about 166 nm. This 3.1 μm emission intensity is enhanced by the introduction of ZnF₂ to the AlF₃-based fluoride glass. Up-conversion emission, strong near-infrared emission, and fluorescence lifetime are enhanced to different degrees by increasing the ZnF₂ content. Moreover, the spectroscopic characteristics of the glass specimens and the highly efficient Er³⁺: ⁴S_3/2 → ⁴F_9/2 transition's energy transfer mechanism were investigated. The absorption spectra and emission spectra of these aluminum fluoride glass specimens were used to calculate their gain coefficients and maximum cross sections at 1.5 and 3.1 μm. Overall, the spectral properties of these prepared aluminum fluoride glass specimens demonstrate their high potential for use as infrared laser host materials.     

Tm3+-doped tellurite glass with Yb3+ energy sensitized for broadband amplifier at 1400-1700 nm bands

A kind of novel experiment was disclosed as it possessed two bands of fluorescence emission at 1.4 and 1.6 μm, which were per-fectly complimentary to the current C band of optic communication. The fluorescence was based on energy transfer and up-conversion proc-esses between Tm3+ and Yb3+ under direct pumping of 975 nm LD. The spectra and lifetimes of Tm3+ fluorescence in the tellurite glass were described. The corresponding fluorescence characteristics and energy migration process were analyzed by the method of lifetime and inten-sity comparison. The mechanism of the up-conversion based IR fluorescence was presented upon analyzing the multi-photon pumping proc-ess. The potential advantages of Tm3+/Yb3+ co-doped tellurite glass as amplifier material were concluded.