Wide-angle Ni-diffused LiNbO3 abrupt waveguide bend witha proton-exchanged microprism

A novel Ni-diffused abrupt waveguide bend on LiNbO₃ using proton-exchanged microprism is presented. With the phase delay caused by the microprism, the guided wavefront can be appropriately tilted such that most of the optical power can be kept within the waveguide after passing through the bend corner. The simulated normalized transmitted power of the proposed waveguide bend can be as high as 93.33% for a bend angle of 10°. The effects of microprism parameters are also discussed to facilitate the optimal design of the proposed waveguide bend. The experimental results show that the proton-exchanged microprism on LiNbO₃ does significantly enhance the transmitted power     

Linear phase tracking in a coherence modulation electrical sensorsystem using integrated LiNbO3 modulator/demodulator

We report an interferometric sensor system, based on coherence modulation of light and LiNbO₃ integrated optics technology. We describe a phase detection scheme designed to retrieve the absolute phase variations produced by a sensor system where the sensor signal is electronically applied to an electro-optic modulator. The system consists of an imbalanced LiNbO₃ Mach-Zehnder transducer fed by a self-powered charge generating sensor, and an optoelectronic central processing unit including a second electrooptic Mach-Zehnder working as an optical demodulator and featuring a matched path-imbalance. Electrical feedback is applied to this second interferometer in an active demodulation scheme, allowing a linear tracking of the signal phase up to 7-π radians     

Layout for polarization insensitive modulation in LiNbO3waveguides

We present in this paper a new waveguide-electrode layout for electrooptical devices integrated in a Z-cut X-propagating lithium niobate crystal. Polarization independent operation is achieved in this structure by a combination of several factors: simultaneous utilization of three electrooptic coefficients (r₃₃ r₃₁ r₂₂), electrode shift with respect to waveguides, and consideration of a necessary insertion of a buffer layer. Phase and amplitude modulation schemes are described based on this configuration. The layout has advantages, when compared to other polarization-insensitive schemes, in terms of lower voltage length and absence of polarization conversion     

Ferroelectric behaviors of sandwich structured PbZr0.52 Ti0.48O3/Pb(Mg1/3Ta2/3)0.7Ti0.3O3/PbZr0.52Ti0.48O3 thin film

Sandwich structured PbZr_0.52Ti_0.48O₃/Pb(Mg_1/3 Ta_2/3)_0.7Ti_0.3O₃/PbZr_0.52Ti_0.48O₃ (PZT/PMTT/PZT) thin films have been successfully synthesized via a combined route involving sol-gel and RF magnetron sputtering. Insertion of the PMTT interlayer effectively suppressed formation of the heterogeneous “rosette” structure of PZT thin film when deposited onto Pt/Ti/SiO₂/Si substrate. While both remanent polarization and coercive field were lowered for the sandwich structured films, the coercive field was reduced more significantly. Such sandwich structured films exhibit improved fatigue behavior and the relative permittivity can not be simply described as a series connection of individual components of perovskite layers.     

Co2O3掺杂WO3陶瓷的电学特性

采用常规的电子陶瓷工艺制备了Co0.04W0.96O3多晶陶瓷,并对样品进行了微观形貌、相结构及Ⅰ-Ⅴ特性测试分析,发现Co0.04W0.96O3多晶陶瓷存在着奇特的负微分电阻特性.微分电阻随电场变化的曲线图揭示了CoW缺陷有着与众不同的特点,正是这种缺陷的存在使得多晶陶瓷具有负微分电阻特性.主要讨论了Co0.04W0.96O3多晶陶瓷负微分电阻特性的产生机制,并提出了二次势垒模型.     

Modeling of passively Q-switched Er/sup 3+//Yb/sup 3+/-codoped clad-pumped fiber lasers

We present the modeling of passively Q-switched Er/sup 3+//Yb/sup 3+/-codoped double-clad fiber lasers (EYDFL). Both two-level and three-level saturable absorbers (SAs) are used. The model is based on detailed rate equations of SAs, Er/sup 3+/, and Yb/sup 3+/ populations in the fiber, and light propagation equations including spontaneous emissions due to both Er/sup 3+/ and Yb/sup 3+/. Laser output characteristics including pulse energy, width, peak power, repetition frequency (PRF), and average power are computed as functions pump power, fiber length, single-mode/multi-mode fibers, Er/sup 3+//Yb/sup 3+/ concentrations, out-coupling reflectivity, focus area on the SA, and SA doping and length. Several transition metal-doped crystal SAs and semiconductor SA mirrors (SESAM) are considered and compared.     

YBa2Cu3O7

Some background information on superconducting ceramics is given, and the history of yttrium barium copper oxide (YBCO) is discussed. The crystal structure of superconducting YBCO is described. The production and extraction methods of bulk samples of YBCO are detailed. Different theories of superconductivity in YBCO are addressed, and applications of YBCO superconductors are discussed     

1865140型(LiMn2O4+LiNi1/3Co1/3Mn1/3O2)/Li4Ti5O12电池的性能

使用锰酸锂(LiMn2O4)、镍钴锰酸锂(LiNi1/3 Co1/3Mn1/3O2)混合正极材料和钛酸锂(Li4 Ti5 O12)负极材料,制备了中倍率1865140型锂离子电池.制备的电池在12 min内可充满电池容量的80％以上,且电池表面温度不超过35℃;在室温下以2.00 C循环1 200次,容量保持率高于91％;在高温55℃下以1.00 C循环1 000次,容量保持率高于82％.FreedomCAR混合脉冲功率特性表明:在放电深度(DOD) 10％ ～ 70％内、10s脉冲充放电状态下,电池的阻抗都在9 mΩ以下;50％DOD时的10s放电比功率为372 W/kg,充电比功率为520 W/kg.     

合成温度对LiNi1/3Co1/3Mn1/33O2结构和电化学性能的影响

采用高温固相法合成了层状LiNi1/3Co1/3Mn1/3O2锂离子正极材料,研究了合成温度及合成时间对材料结构(包括Li-Ni阳离子混排)以及电化学性能的影响。实验结果表明975℃7 h合成的样品具有最好的电化学性能,在0.1 C时2.5～4.3 V间,其首次充放电比容量分别为173.7、149 mAh/g,前10周容量保持95%。精修结果表明所得材料存在Li-Ni阳离子混排,Li层中有5%的位置被Ni所占据。     

Li(Ni1/3Co1/3Mn1/3)O2正极材料的电化学性能

用共沉淀法制备出(Ni1/3Co1/3Mn1/3)(OH)2,与LiOH·H2O混合后,在900℃下焙烧12 h,得到锂离子电池正极材料Li(Ni1/3Co1/3Mn1/3)O2.在2.70～4.35 V,电流为40 mA/g时,循环性能稳定.当截止电压升高到4.60 V时,容量可达190 mAh/g.循环伏安实验表明,材料的结构在循环过程中保持稳定.     

LiNi1/3Co1/4Mn1/3M1/12O2(M=Al,Ti)的性能研究

采用共沉淀法在800℃下煅烧9 h,制备出了LiNi1/3Co1/4Mn1/3M1/12O2(M=Al,Ti).利用XRD、DSC和充放电分析方法对其进行了表征.实验结果表明LiNi1/3Co1/3Mn1/3O2中Al和Ti的加入,提高了材料LiNi1/3Co1/4Mn1/3M1/12O2(M=Al,Ti)在4.3 V下热分解反应的热稳定性.     

Room Temperature Magnetoresistance at Low Magnetic Fields in La0.7 Ba0.3 MnO3

This paper examines the possibility of enhancing the room temperature magnetoresistance at low applied magnetic fields in single layer La_0.7 Ba_0.3 MnO₃ thin films. The influence of lattice mismatch strain, as well as the effect of different frequency regimes, on the magnetoresistance is explored. The effects of lattice mismatch strain are studied by measuring the magnetoresistance as a function of the La_0.7 Ba_0.3 MnO₃ film thickness, oxygen annealing, and lattice matched buffer layers. We find that the release of the lattice mismatch strain improves the magnetoresistance at room temperature and at low magnetic fields. In fact, the highest magnetoresistance at room temperature (–1.7% at 500 Oe) has been found for the 1600 Å as-grown La_0.7 Ba_0.3 MnO₃ film, whereas the largest magnetoresistance (–1.9% at 500 Oe) is found at 309 K for the 1000 Å La_0.7 Ba_0.3 MnO₃ film annealed in flowing O₂ for 1 h at 900°C. Finally, we find that the microwave magnetoresistance is the same as the dc magnetoresistance when the cavity corrections are applied. In the single layer La_0.7 Ba_0.3 MnO₃ system, the low field magnetoresistance at room temperature is far from being technologically viable.     

Postbreakdown Conduction in Ultrathin La2 O3 Gate Dielectrics

The evolution of the conduction characteristics of ultrathin lanthanum oxide (La₂O₃) gate dielectrics that are subjected to constant and ramped electrical stresses was investigated. The samples were obtained by the electron-beam evaporation technique and annealed in situ in ultrahigh vacuum conditions to minimize the formation of an interfacial oxide layer. We have shown that the total current flowing through the device consists of two parallel contributions, where one is associated with direct and Fowler-Nordheim tunneling and the other one is associated with multiple breakdown (BD) path conduction. This latter component is sensitive to the applied stress and evolves from soft BD to diodelike conduction as the degradation proceeds. We analyzed the experimental data in terms of two well-known models for post-BD conduction. The importance of considering series and parallel resistances within these formulations is shown.     

锂离子电池正极材料Li(Ni1/3Co1/3Mn1/3)O2的研究进展

综述了锂离子电池正极材料Li(Ni1/3Co1/3Mn1/3)O2的研究现状.对该材料结构、合成方法、电化学性能及热力学稳定性的研究进展作了较为详细的介绍,并对它的发展进行了展望.     

CaTiO3-NdAlO3系微波介质陶瓷的研究进展

综述了具有中等介电常数的CaTiO3-NdAlO3微波介质陶瓷在晶体结构、制备及反应过程、介电性能等方面的研究进展,总结了该体系微波介质陶瓷研究中存在的问题及其发展趋势.     

NH3/CO2复叠式制冷循环的分析与优化

建立了NH3/CO2复叠式制冷循环的理论分析,结果表明:存在最优蒸发-冷凝器的中间温度使循环的性能系数达到最大,带膨胀机同时过冷NH3/CO2复叠式制冷循环的理论COP优于传统R22/R13复叠循环和NH3双级循环,回热器的换热效果直接影响系统性能.     

Ce3+:LiCaAlF6 crystal for high-gain orhigh-peak-power amplification of ultraviolet femtosecond pulses and newpotential ultraviolet gain medium: Ce3+:LiSr0.8Ca0.2AlF6

To develop high-peak-power ultrashort pulse laser systems in the ultraviolet region, a large Ce³⁺:LiCaAlF₆ (Ce:LiCAF) crystal, a tunable ultraviolet laser medium with large saturation fluence and broad gain spectrum width, was grown successfully with a diameter of more than 70 mm. To demonstrate high small signal gain, a four-pass confocal amplifier with 60 dB gain and 54 μJ output energy was constructed. Chirped pulse amplification (CPA) in the ultraviolet region was demonstrated using Ce:LiCAF for higher energy extraction. A modified bow-tie-style four-pass amplifier pumped by 100-mJ 266-nm 10-Hz pulses from a Q-switched Nd:YAG laser had 370-times gain and delivered 6-mJ 290-nm pulses. After dispersion compensation, the output pulses can be compressed down to 115 fs. This is the first ultraviolet, all-solid-state high-peak-power CPA laser system using ultraviolet gain media, and this demonstration shows further scalability of the Ce:LiCAF CPA system. Additionally, a new gain medium, Ce³⁺ :LiSr_0.8Ca_0.2AlF₆, with longer fluorescence lifetime and sufficient gain spectrum width over 18 nm was grown to upgrade this system as a candidate for a final power amplifier gain module     

Integrated optical, wavelength selective, acoustically tunable2×2 switches (add-drop multiplexers) in LiNbO3

Fully packaged, polarization independent, integrated acoustooptic 2×2 switches have been developed which can be also used as add/drop multiplexers. The devices have been fabricated in X-cut Y-propagating LiNbO₃ and can be operated at wavelengths around 1550 nm. They consist of passive polarization splitters and acoustooptic TE-TM converters with weighted coupling. A filter bandwidth of 2.0 nm and a tuning range of 130 nm have been obtained. The fiber-to-fiber insertion loss is <4.6 dB and a residual polarization dependence of 1.3 dB for bar-state and 0.1 dB for cross-state routing has been achieved     

正极材料LiNi1/3Co1/3Mn1/3O2的研究进展

介绍了LiNi1/3Co1/3Mn1/3O2的晶体结构和作为锂离子电池正极材料的电化学反应特征,总结了合成条件和制备方法对其物理性能和电化学性能的影响,以及不同掺杂元素(B,F,Mg,Fe,Al,Si等)对其的改性作用.