铒镱共掺光纤制备及其激光性能研究

铒镱(Er~(3+)/Yb~(3+))共掺光纤是实现波长为1.5μm激光的重要增益介质之一。但是石英基Er~(3+)/Yb~(3+)共掺光纤很容易产生波长为1μm的放大的自发辐射(ASE)光,不仅降低1.5μm激光的泵浦转换效率,而且是限制1.5μm激光功率提升的"瓶颈"。研究结果表明,提升纤芯磷的掺杂量,能够增大纤芯基质的最大声子能量,有利于抑制Yb~(3+)的ASE光和Er~(3+)→Yb~(3+)的反向能量传递,从而提高Er~(3+)/Yb~(3+)共掺光纤的泵浦转换效率。通过改良的化学气相沉积制备工艺可以减少磷元素在高温条件下的挥发,从而成功制备出高掺磷的10/130μm双包层Er~(3+)/Yb~(3+)共掺光纤。测试光纤后向的1μm ASE光谱随泵浦功率的变化,并且搭建两级激光测试平台,测得Er~(3+)/Yb~(3+)共掺光纤激光的斜率效率为35.5%。     

铒离子在钨酸锌晶体中的光谱性质

本文测量并分析了ZnWO_4∶Er晶体的吸收光谱、激发光谱和荧光光谱,发现Er~(3+)离子与基质晶格之间存在能量传递效应。用Judd-Ofelt理论计算了Er~(3+)离子的强度参数Ω_λ以及吸收和辐射跃迁的振子强度,并由此计算出激光能级辐射跃迁几率、辐射寿命、积分发射截面及荧光分支比等光谱参数。讨论了ZnWO_4∶Er晶体几个主要通道实现激光输出的可能性。     

YAG∶Er~(3+),Ce~(3+)激光晶体的光谱特性

本文采用在YAG晶体中共掺铒铈离子,利用Ce~(3+)离子具有f—d宽带吸收跃迁,提高Er~(3+)离子对泵浦能量的吸收,以降低YAG:Er,Ce晶体的激光阈值。并测定了晶体在室温下的吸收光谱和荧光光谱。讨论了YAG:Er~(3+),Ce~(3+)晶体的光谱特性。用Judd—Ofelt理论计算了晶体中Er~(3+)离子振子强度,并与单掺铒离子YAG:Er~(3+)晶体中的数值进行了比较。     

掺Er~(3+)光纤放大器特性研究

本文综述我们用铁宝石可调谐激光,半导体激光,氩离子激光等不同波长光源泵浦掺Er~(3+)光纤放大器的输出特性,在比较不同光纤长度、不同信号波长(1.536μm,1.52μm)、不同温度(常温、液氮温度)等条件下,掺Er~(3+)光纤放大器的放大增益特性。给出掺Er~(3+)光纤放大器的理论模型,     

Er:YAG ~4I_(11/2)-~4I_(13/2)激光跃迁的动力学过程研究

Er:YAG中Er~(3+)离子的~41_(11/2)—~4I_(13/2)跃迁产生的受激辐射振荡能发射2.938μm激光,它能被生物细胞组织中的水有效地吸收,因而这种激光可发展成很理想的医用激光器。对Er~(3+)的~4I_(111/2)—~4I_(3/2)跃迁形成的激光振荡过程的动力学问题进行研究,将有助于提高Er:YAG晶体的生长技术和质量,改善Er:YAG激光器的性能。     

掺Er~(3+)、掺Nd~(3+)光纤的光谱及其最佳泵浦波长和光源

本文给出掺Er~(3+)、掺Nd~(3+)和普通单模光纤在3800A——18000A波段上的吸收谱,以及关于半导体激光器激发掺Nd~(3+)光纤荧光曲线的实验结果,并对它们的吸收谱进行相互比较,讨论光纤激光器、放大器的最佳泵浦波长,建议用NYAB自倍频激光器作为掺Er~(3+)和Nd~(3+)光纤泵浦光源。     

掺Er~(3+)石英光纤中倍频效应的实验研究

采用一种新的光纤倍频两步激光预处理方法处理掺Er~(3+)石英光纤,并获得8.8％的峰值倍频转换效率。测定了掺Er~(3+)光纤的有效倍频长度,探讨了掺Er~(3+)光纤产生高转换效率倍频光的物理过程。倍频光的脉宽是基频光波的0.7倍和短光纤中倍频光峰值功率随泵浦激光峰值功率平方变化的实验结果表明,倍频光是通过二阶非线性过程产生的。     

光纤非线性问题的研究进展

本文对1987年国外出现的光纤放大器研究进行评述,比较了半导体光放大器、光纤受激喇曼散射和受激布渊里散射的光放大及掺Er~(3+)光纤放大器的行为和特点。对Er~(3+)光纤放大器的实验研究及     

Er~(3+)离子及ErP_5O_(14)晶体的光谱性质

根据ErP_5O_(14)的吸收和荧光光谱,用Judd—Ofelt理论计算了在此晶体中Er~(3+)的强度参数Ω_λ(或τ_λ),由此计算了激光能级辐射跃迁速率、辐射寿命、荧光分支比和积分发射截面等光谱参数。提出了在Peap与强度参数的总和之间存在直线关系的经验公式。讨论了ErP_5O_(14)作为激光材料的可能性。     

光学材料

0118296Er~(3+),Yb~(3+)掺杂氟氧化物微晶玻璃上转换发光的研究[刊]/林葵//光电子·激光.—2001,12(5).—484～487(E)测量了 Er~(3+)掺杂氟氧化物微晶玻璃、Er~(3+),Yb~(3+)掺杂氟氧化物微晶玻璃退火前后3种样品的吸收光谱、上转换发光光谱及其强度随泵浦光强的变化,对比讨论了其上转换发光特性。参80118297金属/介质型纳米复合变色膜[刊]/赖珍荃//功能材料与器件学报.—2001,17(2).—141～146(E)     

自旋对SiC半导体二维磁极化子基态能量的影响

应用线性组合算符和微扰法研究了电子自旋对SiC半导体性质的影响。基态能量E0^＋（对应于电子自旋量子数为正）和E0^-（对应于电子自旋量子数为负）都随磁场增加而线性减少：在0T时，E0^＋和E0^-都为-76．24meV；在25T时，E0^＋和E0^-分别为-68．50meV和71．39meV。自旋能量与E0^＋和E0^-之比P0^＋和P0^-都随磁场增加而快速增加：在0T时，P0^＋和P0^-都为0；在20T时，P0^＋为0．627；在25T时，P0^-为0．453。自旋能量与Landau基态能量之比P2始终为0．23。自旋能量与自能和声子之间相互作用能量之比P1和P3都随磁场增加而线性增加：在0T时，P1和P3都为0；在5T时，P3为0．628；在40T时，P1为0．306。这些数据和结果有助于设计和研制自旋场效应晶体管、自旋发光二极管和自旋共振隧道器件等。     

有机掺杂电致磷光器件中主客体间的能量转移几率

提出了有机掺杂电致磷光器件中主体(TPD)与客体(Ir(ppy)3)间的能量转移几率表达式,并对能量转移过程进行了讨论.结果表明:(1)三态激子能量转移率(KHG,KGH)随主客体分子间距离R指数增加,KHG随客体分子间距离RGG增加有一个快的减少,且KHG/KGH随R或RGG减少而增加;(2)当R为0.8～1.2nm时,能量转移几率接近线性降低,而当R＜1.1nm时,RGG的变化能够被忽略,对于1.1nm＜R＜1.2nm的情况,RGG(＜1.6nm)对η起着越来越重要的作用;(3)当Forster能量转移率增加或Gibb's能减小时,η将会增加.     

Energy‐efficient design of 3D UWSNs leveraging compressive sensing and principal component analysis: A communication techniques perspective

The design of energy‐efficient underwater wireless sensor networks (UWSNs) poses many challenges due to the intrinsic properties of propagation medium and limited battery power of sensor nodes. This paper proposes the concept of optimal clustering for three‐dimensional (3D) UWSNs leveraging compressive sensing (CS) and principal component analysis (PCA) technique of data compression. Optimal clustering reduces the energy consumption by selecting the optimal number of clusters whereas CS and PCA compression techniques reduce the energy consumption by considering a lesser number of samples and reduce the data redundancy at cluster heads (CHs) level, respectively. Moreover, three communication techniques like acoustic, electromagnetic (EM), and free‐space optical (FSO) wave are considered for communication in 3D UWSNs. We compared the energy efficiency for all three communication techniques by examining the three base station (BS) positions at the center, at the corner, and at the lateral midpoint of the 3D sensing area. Moreover, performance parameters (network lifetime, throughput, packet drop rate, and latency) are also evaluated for 3D UWSNs. It is observed that PCA outperforms the CS technique. The proposed technique is suitable for long‐term and densely deployed 3D UWSNs, in which saving energy is of crucial importance.     

硅纳米管结构和电子性质的第一性原理研究

基于密度泛函理论的第一性原理方法,在广义梯度近似下,研究了(5,0)和(5,5)硅纳米管结构和电子性质。计算结果表明:(5,0)管硅原子相邻键长波动范围为0.068 nm,大于(5,5)管的0.006 nm;通过对(5,0)管的分波态密度进行分析发现,其3s电子和2p电子能量分布在-13～3 eV,但2p电子集中分布在能量较高的-6～3 eV,出现了明显的sp3轨道杂化。同时对(5,0)和(5,5)硅纳米管最高占据轨道和最低未占据轨道的能隙进行了分析,发现两种管导电性能与结构的手性相关,锯齿型(5,0)管能带交叠具有明显的金属性,而扶手型(5,5)管能隙为0.151 eV是半导体纳米管。     

Smart Energy Bricks: Ti3C2@Polymer Electrochemical Energy Storage inside Bricks by 3D Printing

Three-dimensional (3D) printing technology has a pronounced impact on building construction and energy storage devices. Here, the concept of integrating 3D-printed electrochemical devices into insulation voids in construction bricks is demonstrated in order to create electrochemical energy storage as an integral part of home building. The low-cost 3D-printed supercapacitor (SC) electrodes are created using graphene/polylactic acid (PLA) filament in any desired shape such as 3D cylindrical- (3Dcy), disk- (3Ddc), and 3D rectangular- (3Drc) shaped electrodes. To obtain excellent capacitive performance, a Ti₃C₂@polypyrrole (PPy) hybrid is uniformly electroplated on the surface of 3D-printed electrodes. These Ti₃C₂@PPy-coated 3D-printed electrodes exhibit outstanding electrical conductivity, capacitive performance, cycle life, and power density. The bricks themselves act as an excellent scaffold for electrochemical energy devices as they are electrically insulating, fire-resistant, and contain substantial unused thermal insulation voids. A 3Drc Ti₃C₂@PPy SC is integrated into a real brick to showcase a smart house energy storage system that allows to reserve power in the bricks and use it as a power backup source in the event of a power outage in the elevator. This concept provides a platform for future truly smart buildings built from added value “smart brick” energy storage systems.     

Tm:Yb:KY(WO4)2晶体蓝光上转换

利用顶部籽晶提拉(TSSG)法生长了Yb3 ,Tm3 共掺KY(WO4)2晶体,在室温下测量了290～1200nm内晶体的吸收光谱。根据上转换模型研究了晶体中Yb3 向Tm3 进行能量传递的机制并对晶体中跃迁能级进行了指认,建立了简单的速率方程。计算得出Yb3 离子向Tm3 离子的能量传递效率接近于1。在974nm激光二极管抽运下观察到Tm3 离子的波长为476nm蓝色上转换发光。利用Fadenbrug-luechtbauer方法计算了1G4到3H6能级跃迁的发射截面积,其最大发射截面积约为1.51×10-20cm2。     

复合钙钛矿弛豫铁电体中极化微区尺寸的确定

通过分析极化微区形成过程中自由能的变化，确定极化微区的尺寸。以相变过程中的潜热做为均匀铁电体顺电态转变为铁电态自由能变化的近似值。随着温度降低，某些区域铁电态自由能密度降低；当铁电态自由能密度低于顺电态自由能密度时导致该区域出现极化，而晶格畸变在微区表面产生的弹性势能随着极化微区长大而逐渐增大，成为阻碍微区长大的主要原因。通过自由能极值分析，所得Pb（Mg1/3 Nb2/3）O3-PbTiO3微区尺寸与实验结果相近。     

Hot electron energy relaxation via acoustic phonon emission in GaAs/Al0.24Ga0.76As single and multiple quantum wells

The energy relaxation associated with acoustic phonons has been investigated in a series of modulation doped GaAs/AlGaAs single and multiple quantum wells grown by molecular beam epitaxy, using the hot electron Shubnikov — de Haas effect. The power loss is shown to be proportional to (T_e² − T_L²) for electron temperatures 2.2K < T_e < 8K and proportional to (T_e³ − T_L³) for 8K < T_e < 20K. The energy loss rates due to acoustic phonon scattering via both deformation potential coupling and piezoelectric coupling have been calculated. The total energy loss rate as a function of electron temperature is compared with the experimental results. Good agreement is obtained for 2.2K < T_e < 8K. Above 8K the energy loss rate is seen to rise above the predicted values, indicating the onset of an extra energy relaxation mechanism. The application of a high electric field (E = 3kV/cm) at low lattice temperatures is shown to induce persistent parallel conduction and a subsequent reduction of the low field well mobility.     

High‐Temperature BiScO3‐PbTiO3 Piezoelectric Vibration Energy Harvester

Conventionally, effective mechanical vibration energy harvesting is based on (Pb,Zr)TiO₃ (PZT) ceramics, poly(vinylidene fluoride) (PVDF) polymers or PVDF/PZT or other piezoelectric composite materials, and their working temperature is normally limited to room temperature (R‐T) or below 150 °C. Here, bismuth scandium lead titanate (BiScO₃‐PbTiO₃, abbreviated as BSPT) ceramic is reported which has a high Curie temperature point around 450 °C and its application for high‐temperature (H‐T) vibration energy harvesting. Experimental results show that it exhibits an excellent H‐T piezoelectricity, converting mechanical vibration energy into electric power effectively in a wide temperature range from R‐T till 250 °C. This research shows the BSPT piezoelectric energy harvester having the potential application for self‐power source of wireless sensor network system in high temperature circumstance.     

XPS Investigation on Surface and Interface Electronic States of Alq3／ITO

The surface and interface electronic states of tris-(8-hydroxyquinoline)aluminum(Alq3)/indium-tin oxid(ITO)were measured and analyzed by X-ray photoelectron spectroscopy(XPS).The results indicated that, in Alq3 molecule,the binding energy(Eb)of Al atoms is 70.7eV and 75.1eV,corresponding to Al(O)and Al(Ⅲ）,respectively;The binding energy of C is 285.8eV,286.3eV,and 286.8eV,corresponding to C of C-C group,C-O,and C-N bond,respectively,N is the main peak locating at 401.0eV, corresponding to Natom of C-N=C.Oatoms mainly bond o H atom,with the binding energy of 533.2 eV.As the sputtering time of Ar^ ion bearn increases,Al2p,C1s,N1s,O1s,Ind3d5/2 and Sn3d5/2 peaks slightly shift towards lower binding energy,and Al2p,C1s and N1s peaks get weaker,which contributed to diffusing the oxygen,indium and tin in ITO into Alq3 layr.