Spectral and Lasing Properties of Er^(3+0/Yb^(3+) Co-Doped Phosphate Glasses Pumped by LD

Er^3 ＋/Yb^3 ＋ phosphate glasses were fabricated. According to McCumber theory, the stimulated emission cross-section of Er^3＋ ions at 1533 nm was calculated on the basis of absorption spectrum, and 0.84 × 10^-20 cm^2 is derived, the fluorescence lifetime of ^4I13/2 level is 8.5 ms. An Er^3＋/Yb^3＋ co-doped phosphate glass CW laser pumped by LD was demonstrated at room temperature. The maximum output power is 80 mW and slope efficiency is 16.5%.

Er^3+,Yb^3+:glass-Co^2+:MgAl2O4 diffusion bonded passively Q-switched laser

A Co^2＋：spinel passively Q-switched erbium-ytterbium-phosphate glass bonded laser pumped at 940 nm is reported.A pulse energy of 210 μJ, a peak power over 70 kW, and beam quality M-2 parameter of 1.2 are obtained under a pump power of 235 mW. An unbonded laser output experiment with the same dimension of the active material and the saturable absorber as the bonded laser output experiment is carried out. The reason why the output in the bonded laser is improved is determined.

Effect of Calcium Phosphate Glass on Dentinal Tubule Sealing after Irradiation with the Carbon Dioxide Laser

The aim of this study was to evaluate the dentinal tubule sealing and acid resistance of dentin specimens following the application of calcium phosphate glass powder prior to irradiation with a CO2(carbon dioxide)laser.Dentin models simulating open dentinal tubules were divided into two groups:experimental(calcium phosphate glass slurry applied to the dentin surface)and control(no slurry applied to the surface).All specimens in the experimental group and five specimens in the control group were irradiated with a CO2 laser.The defocused laser beams(0.5 and 1 W)were applied(spot size,5 mm in diameter)from a distance of 20 mm for 10 s.The surfaces and cross-sectional areas of the specimens were examined using an SEM(scanning electron microscope).In addition,the resistance to acid was evaluated in these specimens.The open dentinal tubules in the control groups were sealed following irradiation with the CO2 laser at 0.5 W and 1.0 W.Likewise,sealing of open dentinal tubules was observed in the experimental group after CO2 laser irradiation.The acid resistance of the dentin surface was improved after CO2 laser irradiation;specimens in the experimental group presented with significantly lower amounts of Ca ion release compared to those in the control group.These findings indicate that CO2 laser irradiation alone or after the application of calcium phosphate glass powder can effectively seal the dentinal tubules and alleviate dentin hypersensitivity.

Preparation and Spectra Properties of BaO-Al_2O_3-P_2O_5-Sm_2O_3 System Protection Glasses

The forming-regions of phosphate glasses doped with high Sm2O3 contents were studied by two step melting method. The relationship between absorption spectrum and rare earth contents was also discussed. The spectra of BASP glasses were measured by spectrophotometer. The results show that the forming regions will shrink with the increase of Al2O3 and it is difficult to form glass when [PO4]/[AlO4] < 2. The forming regions tend to be a closed elliptical, and the intensity of characteristic absorption peak increases gradually with the increase of Sm2O3, the absorption lines broadens non-uniformly and there is approximate linear relation between optical density at the 1064 nm wavelength and Sm2O3 content.

Effect of Network Modifiers on Spectroscopic Properties of Erbium-doped Phosphate Glasses

The integrated absorption cross section Σ abs, peak emis sion cross section σ emi, Judd-Ofeld intensity parameters Ω t(t=2,4,6), and spontaneous emission probability A R of Er 3+ ions were determined fo r Erbium doped alkali and alkaline earth phosphate glasses. It is found the comp ositional dependence of σ emi is almost similar to that of Σ abs, wh ich is determined by the sum of Ω t (3Ω 2+10Ω 4+21Ω 6). In addition, the compositional dependence of Ω t was studied in these glass systems. As a resu lt, compared with Ω 4 and Ω 6, the Ω 2 has a stronger compositional depend ence on the ionic radius and content of modifiers. The covalency of Er-O bonds in phosphate glass is weaker than that in silicate glass, germanate glass, alumi nate glass, and tellurate glass, since Ω 6 of phosphate glass is relatively la rge. A R is affected by the covalency of the Er 3+ ion sites and correspon ds to the Ω 6 value.

掺Nd^(3+)激光材料的研究进展

介绍了掺Nd3+激光离子晶体、陶瓷、玻璃和微晶玻璃材料的研究现状,比较了各种掺Nd3+激光材料的性能,分析了不同的掺Nd3+激光材料的各自用途,评述了有代表性的掺Nd3+激光材料的光谱和激光特性,讨论了掺Nd3+激光材料研究和应用方面的发展趋势。

掺Nd^(3+)含磷氟铝酸盐玻璃光谱特性

本文报导了Nd^(3+)在含磷氟铝酸盐玻璃中的吸收和萤光光谱,并计算了Nd^(3+)的部分吸收光谱性质.根据吸收乐谱性质,应用J-O模型计算了Nd^(3+)离子的发光特性.指出在RF_2-AlF_3-YF_3系统氟化物玻璃中,引入一定量的Ba(PO_3)_2(<10mol%),对Nd^(3+)离子部分吸收中心波长,线宽影响不大,而吸收截面略有提高,对Nd^(3+)离子的发光性质可得到改善,更适合于作纤维激光器中光纤的基质玻璃.

掺Nd^(3+)硼硅酸盐玻璃的非线性光学特性

在调Q纳秒Nd:YAG强激光脉冲下,使用闭孔Z-扫描技术研究了硼硅酸盐基质玻璃及其掺Nd3+玻璃的三阶光学非线性特性。发现基质玻璃具有正的三阶非线性折射系数和非线性吸收系数,属于自聚焦反饱和吸收型的光学介质;而随着Nd3+的掺入,该硼硅酸盐玻璃的三阶非线性折射和吸收系数较基质玻璃有明显的增大,远高于一个量级。用开孔Z-扫描实验与光限幅实验进一步验证了掺Nd3+玻璃具有较高的三阶非线性吸收系数,表明Nd3+的掺入提高了硼硅酸盐玻璃在532 nm处的激光防护性能。

Effect of copper impurity on the optical loss and Nd^(3+) nonradiative energy loss of Nd-doped phosphate laser glass

N31-type phosphate laser glasses doped with different concentrations of Cu were prepared. Their optical loss coefficient at 1053 nm wavelength and nonradiative transition rate from the Nd3＋ 4F3/2 state were determined and analyzed in detail. The optical loss coefficient per unit of Cu2＋ （cm–1/ppmw） and the fluorescence decay rate （Hz/ppmw） caused by Cu2＋ and Nd3＋ interaction were 0.0024 and 7.9, respectively. Cu impurity affected both optical loss at 1053 nm and fluorescent emission of Nd3＋ 4F3/2 state seriously in N31 laser glass.

Nd^(3+)/Yb^(3+)共掺磷酸盐玻璃光纤的发光与激光特性研究

以970 nm和808 nm半导体激光器作为抽运源,从光纤长度和抽运功率两个方面,探讨了Nd^(3+)/Yb^(3+)摩尔浓度比约为4:1的共掺磷酸盐玻璃光纤的发光与激光特性.在970 nm抽运下,光纤光谱以Yb^(3+)离子的发光为主,但Yb^(3+)→Nd^(3+)能量传递会对光纤光谱(激光和受激放大自发辐射)产生调制作用,调制作用随970 nm抽运功率或光纤长度的增加而显著,甚至出现显著的双波长激光现象.尽管玻璃样品中Nd^(3+)→Yb^(3+)的能量传递效率ηNd→Yb高达64%,但在808 nm抽运下,激光峰始终在1053 nm附近产生,且与808 nm抽运功率大小和光纤长度无关.为解释这一现象,推导了考虑Nd^(3+)离子受激辐射的能量传递模型.从理论模型来看,Nd^(3+)→Yb^(3+)能量传递作用随Nd^(3+)离子受激辐射信号光强度的增加而迅速减弱,这与该光纤实际测试的荧光光谱随808 nm抽运功率的变化规律相符合.因此,当采用Nd^(3+)离子来敏化Yb^(3+)离子时,需要考虑Nd^(3+)离子的受激辐射对Nd^(3+)→Yb^(3+)能量传递的抑制作用.

飞秒激光在掺Nd^(3+)光热敏折变玻璃中写入光波导

利用中心波长1 028nm、重复频率50kHz、脉冲宽度220fs的超短脉冲激光在掺Nd^(3+)光热敏折变玻璃中刻写双线型和压低包层管状波导.研究了激光功率、波导双线间距、管状波导直径对近场模式的影响,得到了两组导光模式较优的波导.利用波导的近场模式强度分布重构了其折射率分布图,得到两类波导最大的折射率增加量分别为+7.0×10^(-4)和+5.5×10^(-4).利用散射法测得双线型波导的传输损耗为1.29dB/cm;通过测量插入损耗得到压低包层管状波导的传输损耗小于1.95dB/cm.利用飞秒激光在掺Nd^(3+)光热敏折变玻璃中直接写入光波导,在集成光学器件上具有广阔的应用前景.

Nd^(3+)掺杂磷酸盐激光玻璃猝灭浓度的计算与预测

通过研究稀土离子在玻璃中激发态布居数与掺杂浓度之间的关系,建立了一种半定量的激光玻璃发光猝灭浓度预测的研究方法。研究发现,在Nd^(3+)掺杂磷酸盐玻璃中,无辐射跃迁速率与浓度的线性相关性大于其与浓度的平方相关性,表明OH-对无辐射跃迁几率的影响大于稀土离子之间的能量传递过程。选择低浓度下的荧光寿命代替自发辐射跃迁寿命预测猝灭浓度,有效降低了多声子弛豫以及OH-的影响,预测发光猝灭浓度与实验值的绝对误差从0.82%降低到了0.16%。本文所提出的预测计算方法具有较高的准确性和普适性,这为理论预测激光玻璃的猝灭浓度提供了一定的指导意义,有助于新型激光玻璃的研究和探索。

Large aperture N31 neodymium phosphate laser glass for use in a high power laser facility

Large aperture Nd:phosphate laser glass is a key optical element for an inertial confinement fusion(ICF) facility. N31,one type of neodymium doped phosphate glasses, was developed for high peak power laser facility applications in China. The composition and main properties of N31 glass are given, together with those of LHG-8, LG-770, and KGSS-0180 Nd:phosphate laser glasses, from Hoya and Schott, and from Russia. The technologies of pot melting, continuous melting, and edge cladding of large size N31 phosphate laser glass are briefly described. The small signal gain profiles of N31 glass slabs from both pot melting and continuous melting at various values of the pumping energy of the xenon lamp are presented. N31 glass is characterized by a stimulated emission cross section of 3.8 × 10-20cm2 at 1053 nm,an absorption coefficient of 0.10–0.15% cm-1at laser wavelength, small residual stress around the interface between the cladding glass and the laser glass, optical homogeneity of ～2 × 10-6in a 400 mm aperture, and laser damage threshold larger than 42 J/cm2 for a 3 ns pulse width at 1064 nm wavelength.

Research and development of new neodymium laser glasses

This work presents a brief introduction on three kinds of newly developed Nd^(3+)-doped laser glasses in Shanghai Institute of Optics and Fine Mechanics(SIOM), China. Two Nd^(3+)-doped phosphate glasses with lower thermal expansion coefficient and thermal shock resistance 4 times higher than that of N31 glass are developed for laser processing.Nd:Silicate and Nd:Aluminate glasses with peak emission wavelength at 1061 and 1065 nm, effective emission bandwidth of 34 and 50 nm, respectively, are developed for Exawatt-class laser system application. Fluorophosphate glasses with low nonlinear refractive index(n_2=0.6–0.86) and long fluorescence lifetime(430–510 μs) are investigated for the purpose of decreasing B integral in high-power laser system. The properties of all these glasses are presented and compared with those of commercial neodymium laser glasses.

Thermodynamic study on elimination of platinum inclusions in phosphate laser glasses for inertial confinement fusion applications

A new method to calculate the formation enthalpies and free energies of compounds based on standard electromotive force of cation,φ0, and free energies of formation, ΔG2980, or formation enthalpies, ΔH2980, of chloride was proposed. A linear relationship between φ0 and ΔG2980, φ0 and ΔH2980, and ΔG2980 and ΔH2980 was found respectively. The parameters used for thermodynamic calculation were calculated. The calculated values of the formation enthalpies and the free energies of formation of platinum compounds, such as Pt3（PO4）2 and Pt （PO3）2,were given for the first time. The mechanism of eliminating platinum inclusions in phosphate laser glass by POCI3 gas bubbling was interpreted from thermodynamic aspect.

掺钕钇铝钙钛晶体激光结合两种再矿化制剂与早期釉质龋的再矿化

背景:近年来,多种激光被广泛应用于口腔医学相关的各种疾病,包括龋病的预防及治疗。目的:探讨掺钕铝酸钇晶体(neodymium-doped:yttrium aluminum perovskite,Nd:YAP)激光联合两种再矿化制剂对早期釉质龋再矿化的作用。方法:将60颗牙釉质块体外建立人工龋模型后,随机分为6组(n=10):A组不进行任何处理,行体外pH循环;B组进行护牙素(主要成分为酪蛋白磷酸钙复合体)再矿化处理,行体外pH循环;C组进行舒适达牙膏(主要成分为生物活性玻璃)再矿化处理,行体外pH循环;D组进行Nd:YAP激光照射,行体外pH循环;E组进行Nd:YAP激光照射,然后进行护牙素再矿化处理,行体外pH循环;F组进行Nd:YAP激光照射,然后舒适达牙膏再矿化处理,行体外pH循环;再矿化处理2次/d,实验周期20 d。G组为正常对照,未致龋,未进行再矿化处理,仅行体外pH循环。实验结束后,检测各组牙釉质表面的显微硬度、形貌与Ca/P比值。结果与结论:①B、C、D组牙釉质表面的硬度值高于A组(P<0.0001),E、F组牙釉质表面的硬度值明显高于B、C、D组(P<0.0001),F组牙釉质表面的硬度值明显高于E组(P<0.0001);②扫描电镜下可见,A组牙釉质表面存在大量的脱矿孔隙;B组牙釉质表面有矿物质沉积,沉积不均匀且较为疏松;C组牙釉质表面有大量矿物质沉积,且钙化团块间可见脱矿孔隙;D组牙釉质表面较为平整,脱矿孔隙较A组明显变小,釉柱间质有破坏;E组牙釉质表面矿物质沉积较厚,脱矿孔隙明显减少;F组牙釉质表面沉积的矿化物最为致密且均匀,脱矿孔隙细小;③B、C组牙釉质表面Ca/P比值明显高于A组(P<0.0001),E组牙釉质表面Ca/P比值明显高于B、C、D组(P<0.0001),F组牙釉质表面Ca/P比值高于E组(P<0.001);③结果显示,生物活性玻璃、酪蛋白磷酸钙复合体、Nd:YAP激光在牙釉质脱矿后均具有促进牙釉质表面再矿化的作用,Nd:YAP激光联合生物活性玻璃或酪蛋白磷酸钙复合体能进一步加强牙釉质龋的再矿化作用,其中Nd:YAP激光和生物活性玻璃的联合使用效果最佳。

Monolithic edge-cladding process for the elliptical disk of N31-type Nd-doped high-power laser glass

This paper investigates the monolithic edge-cladding process for the elliptical disk of N31-type Nd-doped phosphate laser glass,which will be utilized under liquid cooling conditions for high-power laser systems.The thermal stress,interface bubbles and residual refiectivity,which are due to high-temperature casting and bonding during the monolithic edge-cladding process,are simulated and determined.The applied mould is optimized to a rectangular cavity mould,and the casting temperature is optimized to 1000℃.The resulting lower bubble density makes the mean residual refiectivity as low as 6.75×10^(-5),which is enough to suppress the amplified spontaneous emission generated in the Nd-glass disk,and the resulting maximum optical retardation is converged to 10.2–13.3 nm/cm,which is a favourable base for fine annealing to achieve the stress specification of less than or equal to 5 nm/cm.After fine annealing at the optimized 520℃,the maximum optical retardation is as low as 4.8 nm/cm,and the minimum transmitted wavefront peak-to-valley value is 0.222 wavelength(632.8 nm).An N31 elliptical disk with the size of 194 mm×102 mm×40 mm can be successfully cladded by the optimized monolithic edge-cladding process,whose edge-cladded disk with the size of 200 mm×108 mm×40 mm can achieve laser gain one-third higher than that of an N21-type disk of the same size.

Properties of steady-state in Er^(3+)-Yb^(3+)co-doped phosphate glass for optical waveguide laser

Transitions of laser diode （LD） pumped Er^3＋-yb^3＋ co-doped glass laser are rather complicated. Considering energy transfer between Er^3＋ and Yb^3＋ ions, cross-relaxation, upconversion luminescence, and other transition processes, rate equations of quasi-three energy-level-system of the Er^3＋-yb^3＋ co-doped laser are presented. The output characteristics are also calculated and analyzed in detail. The results show that Er^3＋-yb^3＋ co-doped phosphate waveguide lasers with high slope efficiency and low threshold can be achieved.

Study on relaxation oscillation of Er^(3+)/Yb^(3+) co-doped phosphate glass optical waveguide laser

Based on the principle and fabrication of the optical waveguide laser,and through the configuration of the energy level of Er3+/Yb3+ co-doped system,the time-dependent rate equations are formed and then solved by Runge-Kutta algorithm.The dynamic characteristic of the waveguide laser pumped unidirec-tionally by 980 nm LD is analyzed.The curves of the relaxation oscillation are drawn,showing that the photon number and inverted population vary alternately.The attenuation characteristic of the peak power is studied.It is gained that time constant changes with pump power,length of waveguide and the reflectivity of output mirror.Furthermore,the impact of the above three parameters on the frequency and end-time of relaxation oscillation is discussed.The frequency of relaxation oscillation is propor-tional to the pump power.Under high reflectivity conditions,the length of waveguide has a weak impact on the frequency.The end-time decreases as the three parameters increase.These features and results provide a theoretical basis for designing the Er3+/Yb3+ co-doped phosphate optical waveguide laser.