Effect of Ce2O3 on the 1.53 μm spectroscopic properties in Er3+-doped tellurite glasses

Er3+/Ce3+co-doped tellurite-based glasses with composition of TeO 2-Zn O-Na2O are prepared by high-temperature melt-quenching technique.Effects of Ce2O3 content on the 1.53μm band fluorescence spectra and fluorescence lifetime of Er3+are measured and investigated.It is found that the tellurite glass containing Ce2O3 with molar concentration of 0.25%exhibits an increment of 13%in 1.53μm fluorescence intensity and an increment of 15%in the 4I13/2 level lifetime.The results indicate that the prepared tellurite-based glass with a suitable Er3+/Ce3+codoping concentration is an excellent gain medium applied for broadband Er3+-doped fiber amplifier(EDFA)pumped with a980 nm laser diode.     

Effect of Ce2O3 on the 1.53 μm spectroscopic properties in Er3+-doped tellurite glasses

The crown-like zinc oxide(Zn O)samples,which are composed of a hexagonal cap and a tower-like shaft,are prepared by vapor transport method.The hexagonal cap,working as a whispering gallery mode(WGM)resonant cavity,demonstrates density-dependent ultraviolet(UV)lasing emission with a broadened and squared photoluminescence(PL)profile under UV excitation at 355 nm.Theoretical analyses based on Fermi golden rule show that the broadened spectrum profile results from the special optical mode density characteristics in a WGM micro-cavity,which is in agreement with the observed results.     

Structure and spectroscopic properties of Er3+/Ce3+ co-doped TeO2-Bi2O3-TiO2 glasses modified with various WO3 contents for 1.53 μm emission

The Er^3＋/Ce^3＋ co-doped tellurite-based glasses （TeO2-Bi2O3-TiO2） modified with various WO3 contents are prepared using conventional melt-quenching technique. The X-ray diffraction （XRD） patterns and Raman spectra of glass sam- ples are measured to investigate the structures. The absorption spectra, the up-conversion emission spectra, the 1.53 /am band fluorescence spectra and the lifetime of Er3＋：4113/2 level are measured, and the amplification quality factors of Er3＋ are calculated to evaluate the effect of WO3 contents on the 1.53 μm band spectroscopic properties. With the in- troduction of WO3, it is found that the prepared tellurite-based glasses maintain the amorphous structure, while the 1.53 μm band fluorescence intensity of Er3＋ is improved evidently, and the fluorescence full width at half maximum （FWHM） is broadened accordingly. In addition, the prepared tellurite-based glass samples have larger bandwidth qual- ity factor than silicate and germanate glasses. The results indicate that the prepared Er3＋/Ce3＋ co-doped tellurite-based glass with a certain amount of WO3 is an excellent gain medium applied for the 1.53 μm band Er3＋-doped fiber ampli- fier （EDFA）.     

Enhancement of fluorescence emission and signal gain at 1.53 µm in Er3+/Ce3+ co-doped tellurite glass fiber

Er3+/Ce3+ co-doped tellurite glasses with composition of TeO2-GeO2-Li2O-Nb2O5 were prepared using conventional melt-quenching technique for potential applications in Er3+-doped fiber amplifier (EDFA). The absorption spectra, up-conversion spectra and 1.53 µm band fluorescence spectra of glass samples were measured. It is shown that the 1.53 µm band fluorescence emission intensity of Er3+-doped tellurite glass fiber is improved obviously with the introduction of an appropriate amount of Ce3+, which is attributed to the energy transfer (ET) from Er3+ to Ce3+. Meanwhile, the 1.53 µm band optical signal amplification is simulated based on the rate and power propagation equations, and an increment in signal gain of about 2.4 dB at 1 532 nm in the Er3+/Ce3+ co-doped tellurite glass fiber is found. The maximum signal gain reaches 29.3 dB on a 50 cm-long fiber pumped at 980 nm with power of 100 mW. The results indicate that the prepared Er3+/Ce3+ co-doped tellurite glass is a good gain medium applied for 1.53 µm broadband and high-gain EDFA.     

Improvement of 1.53 μm emission and energy transfer of Yb3+/Er3+ co-doped tellurite glass and fiber

To improve the 1.53 μm band emission of Er³⁺, the trivalent Yb³⁺ ions were introduced into the Er³⁺ single-doped tellurite glass with composition of TeO₂–ZnO–La₂O₃, a potential gain medium for Er³⁺-doped fiber amplifier (EDFA). The improved effects were investigated from the measured 1.53 μm band and visible band spontaneous emission spectra together with the calculated 1.53 μm band stimulated emission (signal gain) spectra under the excitation of 975 nm laser diode (LD). It was found that Yb³⁺/Er³⁺ co-doping scheme can remarkably improve the visible band up-conversion and the 1.53 μm band fluorescence emission intensity, and meanwhile improves the 1.53 μm band signal gain to some extent, which were attributed to the result of the effective energy transfer of Yb³⁺:²F_5/2 + Er³⁺:⁴I_15/2 → Yb³⁺:²F_7/2 + Er³⁺:⁴I_11/2. The quantitative study of energy transfer mechanism was performed and microscopic energy transfer parameters between the doped rare-earth ions were determined. In addition, the spectroscopic properties of Er³⁺ were also investigated from the measured absorption spectrum according to the Judd–Ofelt theory, and the structure behavior and thermal stability of the prepared tellurite glass were analyzed based on the X-ray diffraction (XRD) and differential scanning calorimeter (DSC) measurements, respectively.     

Er3+/Yb3+共掺Bi2O3-GeO2-Na2O玻璃的上转换发光

研究了不同Er3 /Yb3 掺杂比46Bi2O3-44GeO2-10Na2O(B46G44N10)(摩尔分数)玻璃的吸收光谱、红外吸收谱和上转换光谱性质,分析了玻璃中Yb3 敏化Er3 的上转换发光机制。测试了Er3 离子在不同Yb3 浓度下玻璃中的上转换荧光强度,得到最佳的掺杂质量比Er3 ∶Yb3 =1∶6。计算了在980 nm激发下Er2O3质量分数为0.5%和Yb2O3质量分数为3.0%的Er3 /Yb3 共掺B46G44N10玻璃的绿光上转换效率为2.27×10-4。比较了不同基质材料玻璃的上转换效率,结果表明B46G44N10玻璃是一种良好的上转换基质材料。     

Er3 /Yb3 共掺TeO2-WO3-Bi2O3玻璃的光谱性质

用高温熔融法制备了Er3+/Yb3+共掺的TeO2-WO3-Bi2O3玻璃,研究了该玻璃的吸收和荧光光谱性质.应用Judd-Ofelt(JO)理论计算了Er3+的谱线强度、自发辐射跃迁几率、荧光分支比和辐射寿命等光谱参数,并拟合了相应的强度参数Ωt(t＝2,4,6).Er3+在该玻璃中4I13/2→4I15/2发射的荧光半高宽(FWHM)为77nm,应用McCumber理论计算的受激发射截面为1.03×10-20cm2.其带宽特性FWHM×σpeake乘积优于掺Er3+的硅酸盐、磷酸盐和铋酸盐玻璃,说明这是一种制备宽带光纤放大器的优良基质材料.Er3+在400～850nm波长范围存在着5个上转换发射峰,分别对应Er3+的激发态4I7/2、2H11/2、4S3/2、4F9/2和4I9/2到基态4I15/2的发射,分析了其可能存在的上转换过程.     

Enhancement of 2.0 µm fluorescence emission in new Ho3+/Tm3+/Yb3+ tri-doped tellurite glasses

For enhancing the 2.0 µm band fluorescence of Ho3+, a certain amount of WO3 oxide was introduced into Ho3+/Tm3+/Yb3+ tri-doped tellurite glass prepared using melt-quenching technique. The prepared tri-doped tellurite glass was characterized by the absorption spectra, fluorescence emission and Raman scattering spectra, together with the stimulated absorption, emission cross-sections and gain coefficient. The research results show that the introduction of WO3 oxide can further improve the 2.0 µm band fluorescence emission through the enhanced phonon-assisted energy transfers between Ho3+/Tm3+/Yb3+ ions under the excitation of 980 nm laser diode (LD). Meanwhile, the maximum gain coefficient of Ho3+ at 2.0 µm band reaches about 2.36 cm-1. An intense 2.0 µm fluorescence emission can be realized .     

Yb:Er:Al2O3材料1.53μm光致发光特性数值分析

考虑两级合作上转换、激发态吸收和交叉弛豫等非线性效应,建立了镱铒共掺氧化铝材料体系的八个能级的速率方程,唯象地构造了合作上转换、激发态吸收、交叉弛豫等系数随镱铒掺杂浓度的变化函数,数值模拟了Yb:Er:Al2O3材料1.53μm光致发光强度与掺杂浓度、抽运功率的变化关系.计算结果表明:掺铒浓度、抽运功率一定时,存在一个最佳的镱掺杂浓度;掺铒浓度一定,最佳的镱铒浓度比值随抽运功率的增强而下降;抽运功率一定,优化的镱铒浓度比值随掺铒浓度的升高而下降.计算结果与实验测量结果相吻合.     

Performance of Er3+-doped chalcogenide glass MOF amplifier applied for 1.53 μm band

A model of Er3＋-doped chalcogenide glass （GasGe20Sb10S65） microstructured optical fiber （MOF） amplifier under the excitation of 980 nm is presented to demonstrate the feasibility of it applied for 1.53 μm band optical communications. By solving the Er3＋ population rate equations and light power propagation equations, the amplifying performance of 1.53 μm band signals for Er3＋-doped chalcogenide glass MOF amplifier is investigated theoretically. The results show that the Er6＋-doped chalcogenide glass MOF exhibits a high signal gain and broad gain spectrum, and its maximum gain for small-signal input （-40 dBm） exceeds 22 dB on the 300 cm MOF under the excitation of 200 mW pump power Moreover, the relations of 1.53 μm signal gain with fiber length, input signal power and pump power are analyzed. The results indicate that the Er3＋-doped Ga5Ge20Sb10S65 MOF is a promising gain medium which can be applied to broadband amplifiers operating in the third communication window.     

Enhanced emission at 2.85 μm of Ho3+/Pr3+ co-doped α-NaYF4 single crystal

The Ho³⁺/Pr³⁺ co-doped NaYF₄ single crystals with various Pr³⁺ concentrations and constant Ho³⁺ molar percentage of ~1% were grown by an improved Bridgman method. Compared with the Ho³⁺ single-doped NaYF₄ crystal, an obviously enhanced emission band at 2.85 μm is observed under 640 nm excitation. The Judd-Ofelt strength parameters (Ω ₂, Ω ₄ and Ω ₆) are calculated, the radiative transition probabilities (A), the fluorescence branching ratios (β) and the radiative lifetime (τ _rad) are obtained in the meantime. The energy transfer from Pr³⁺ to Ho³⁺ and the optimum fluorescence emission of Ho³⁺ ions around 2.85 μm are investigated. Moreover, the maximum emission cross section of above samples at 2.85 μm is calculated to be 0.72×10^-20 cm² for the NaYF4 single crystal with Ho³⁺ molar percentage of 1% and Pr³⁺ molar percentage of 0.5% according to the measured absorption spectrum. All results suggest that the Ho³⁺/Pr³⁺ co-doped NaYF₄ single crystal may have potential applications in mid-infrared lasers.     

Enhanced emission of 2.9 μm from Ho3+/Pr3+ co-doped LiYF4 crystal excited by 640 nm

The use of Pr3+co-doping for great enhancement of mid-infrared(mid-IR) emissions at 2.9 μm and 2.4 μm is investigated in the Ho3+/Pr3+co-doped LiYF4 crystals.With the introduction of Pr3+ions,the fluorescence lifetime of Ho3+:5I7 level is 2.15 ms for Ho3+/Pr3+co-doped crystal,and the lifetime for Ho3+singly doped crystal is 17.70 ms,while the lifetime of Ho3+:5I6 level decreases slightly from 2.11 ms for Ho3+:LiYF4 to 1.83 ms for Ho3+/Pr3+:LiYF4.It is also demonstrated that the introduction of Pr3+greatly increases the mid-infrared emission of Ho3+:5I6 →5I7 which depopulates the Ho3+:5I7 level,while it has little influence on the Ho3+:5I6 level,which is beneficial for greater population inversion and laser operation.The analysis on the decay curves of the 2.0 μm emissions in the framework of the Inokuti-Hirayama model indicates that the energy transfer from Ho3+to Pr3+is mainly from electric dipole-dipole interaction.The calculated efficiency of energy transfer from Ho3+:5I7 to Pr3+:3F2 level is 87.53% for Ho3+/Pr3+(1.02%/0.22%) co-doped sample.Our results suggest that the Ho3+/Pr3+co-doped LiYF4 single crystals may have potential applications in mid-IR lasers.     

Influence of film growth conditions on the transport properties of YBa2Cu3O7−δ step-edge junctions

In order to investigate the influence of film growth conditions on the transport properties of step-edge junctions, YBa₂Cu₃O_7−δ films were deposited on high-quality substrate steps by DC-sputtering at two different substrate temperatures and by off-axis laser ablation. RSJ-like junction properties and a low (1σ)-spread of the critical current density J_c (4.2 K) of 17% along one step were obtained for laserablated junctions. The transport properties of the differently prepared junctions correlated with the microstructure of the step region. This, in turn, might result from the large differences in surface diffusion during film growth.     

Effect of strontium nitride on the properties of Sr2Si5N8∶Eu2+ red phosphor

The nitride phosphor Sr2Si5Ng:Eu2+ was synthesized by the high temperature solid-state method. The properties of Sr2Si5N8:Eu2+ were discussed by X-ray diffraction (XRD) scanning electron microscope (SEM) and spectra analysis. The XRD pattern shows that the single phase produces when strontium nitride is a bit excessive. The SEM photo implies that the excessive strontium nitride works as a flux in the reaction system. The position of emission peak is also located at about 612 nm as strontium nitride is excessive. The luminescent intensity of the phosphor adding excessive strontium nitride is higher than that of the phosphor introducing stoichiometric strontium nitride. The optimized content of nitride strontium was 2.05 mol/mol for the obtained phosphor with excellent properties.     

Effect of Ag doping on the electrical properties of thermally deposited CdS–La2O3 TFTs

This paper describes a new approach for repairing memories. Repair is implemented by deletion of either rows and/or columns on which faulty cells lie. These devices are commonly referred to as redundant memories, because redundant columns and rows are added. A new repair technique and an algorithm are proposed. The algorithm is based on a fault-counting technique and on a reduced-covering approach. The innovative feature is that reduced covering permits an heuristic, but efficient, criterion to be included in the selection of the rows and/or columns to be deleted. This retains independence of the repair process on the distribution of faulty cells in memory, while allowing a good repairability/ unrepairability detection. The main benefits that result by using the proposed repair algorithm are a reduction in execution time to determine the repair-solution for the device under test and its suitability for implementation in a defect analysis system. Illustrative examples and theoretical results are provided to substantiate the validity of the proposed repair technique     

320 × 240 CMOS array for the spectral range of 3–5 μm based on PtSi photodiodes

The results of research and development of a 320 × 240 platinum silicide focal plane array (FPA) for the spectral range of 3–5 μm are presented. The development is based entirely on CMOS technology. It is shown that the FPA makes it possible to adjust the photosignal accumulation time at a fixed frame rate and subtract the background constant component in the output device.     

Investigation of Stimulated Emission from HgTe/CdHgTe Quantum-Well Heterostructures in the 3–5 μm Atmospheric Transparency Window

Semiconductors - Stimulated emission based on interband transitions depending on the pumping wavelength is studied for heterostructures with Hg(Cd)Te/CdHgTe quantum wells in the wavelength region...     

Influence of the surface roughness of the bottom electrode on the resistive-switching characteristics of Al/Al2O3/Al and Al/Al2O3/W structures fabricated on glass at 300 °C

Resistive-switching devices based on Metal–Insulator–Metal (MIM) structures have shown promising memory performance characteristics while enabling higher density of integration. Usually, these MIM devices are fabricated using different processing conditions including high temperature thermal treatments that could lead to undesirable chemical reactions in the insulator material and at its interface with the metals involved. In this work, we compare the electrical characteristics of MIM devices (fabricated on glass at 300 °C) that use aluminum or tungsten as bottom electrode (BE) in order to study the influence of a highly reactive (aluminum) or inert (tungsten) metal electrode on the memory characteristics. We found that the switching characteristics of Al₂O₃ (from a high-resistance state HRS to a low-resistance state LRS and vice versa), are highly dependent on the surface roughness of the BE, the thickness of Al₂O₃ and the current compliance (CC) which limits the electron density flowing through both top/bottom electrodes.