Design and analysis of spectral beam combining system for fiber lasers based on a concave grating

A novel fiber laser spectral beam combining scheme based on a concave grating is presented.The principle of the presented system is analyzed,and a concave grating with blazed structure for spectral beam combining is designed.The combining potential of the system is analyzed,and the results show that 39 Yb-doped fiber laser can be spectrally beam combined via the designed system.By using scalar diffraction theory,the combining effect of the system is analyzed.The results show that the diffraction efficiency of the designed concave grating is higher than 72% over the whole gain bandwidth,and the combining efficiency is 73.4%.With output power of 1 kW for individual fiber laser,combined power of 28.6 kW can be achieved.     

Generation of four-photon GHZ states based on interaction between a four-level atom and two bimodal cavities

A simple scheme is presented for generating four-photon Greenberger-Horne-Zeilinger (GHZ) states with interaction between a four-level atom and two bimodal cavities. In the proposed protocol, the quantum information is encoded on Fock states of the cavity fields. The detection of the atom can collapse the cavity to the desired state. The experimental feasibility of our proposal is also discussed.     

大功率CO_2激光器非平衡态合成WO_3/Al_2O_3新型陶瓷催化剂

用大功率 CO2 激光在高温、快速、非平衡态下合成 WO3/ Al2 O3烯烃歧化反应催化剂。利用 XRD、XPS、DTA TG等技术对催化剂的性质进行了研究。表明激光合成催化剂中存在非平衡态的 Alx WO3。低于六价的钨是烯烃歧化反应的活性中心 .同时还考查了催化剂组成、激光功率及熔炼时间与丙烯歧化反应活性之间的关系。     

温度气压对高分辨力光刻物镜像质影响研究

分析温度气压对物镜光学材料、透镜厚度间隔,以及空气折射率的影响,并用空气折射率对物镜像质影进行模拟计算。研究表明物镜焦面产生较大漂移,对僧率有一定影响,而对畸变影响较小,指出对物镜进行温度气压控制补偿是必要的。     

MBE生长的高质量AlGaAs/InGaAs双δ掺杂PHEMT结构的材料

用 MBE方法制备的 PHEMT微结构材料 ,其 2 DEG浓度随材料结构的不同在 2 .0— 4.0× 1 0 12 cm- 2 之间 ,室温霍耳迁移率在 50 0 0— 650 0 cm2 · V- 1· s- 1之间 .制备的 PHEMT器件 ,栅长为 0 .7μm的器件的直流特性 :Idss～ 2 80 m A/mm,Imax～ 52 0— 580 m A/mm,gm～ 32 0— 40 0 m S/mm,BVDS>1 5V( IDS=1 m A/mm) ,BVGS>1 0 V,微波特性 :P0 ～ 60 0— 90 0 m W/mm,G～ 6— 1 0 d B,ηadd～ 40— 60 % ;栅长为 0 .4μm的器件的直流特性 :Imax～ 80 0 m A/mm,gm>40 0 m S/mm.     

Research and Development of Electronic and Optoelectronic Materials in China

A review on the research and development of electronic and optoelectronic materials in China, including the main scientific activities in this field, is presented. The state\|of\|the\|arts and prospects of the electronic and optoelectronic materials in China are briefly introduced, such as those of silicon crystals, compound semiconductors, synthetic crystals,especially nonlinear optical crystals and rare\|earth permanent magnets materials, etc., with a greater emphasis on Chinese scientist's contributions...     

基于Web服务的电子支付系统研究与设计

目前电子支付系统的最大问题就是安全问题与共享问题.文中提出灵活的应用多种安全技术与Web服务的电子支付系统的概念.并用Web logic8.0实现一个BtoC模式的支付系统的原型.     

The Amplitude of Longitudinal Characteristic Modes in Dielectric Waveguide Array

It's not adequate to just obtain eigenvalue for solving eigenvalue problem. Since the eigenvalues associated with longitudinal characteristic modes in dielectric waveguide array (DWA) has been studied, the paper concentrates on the corresponding eigenvector, namely, the amplitude of these characteristic modes. Through numerical study of the amplitude of longitudinal guided TE and TM modes in DWA, space harmonic (SH) coupling and energy conversion effect have been discovered. The paper not only contribute to deep understand the mechanism of SH interaction, but also do good to analyze the resonance, radiation problem in DWA.     

基于脉冲调制的GSM语音信道数据传输方法

针对全球移动通信系统 (GSM) 的安全机制不能实现端到端安全通信问题,提出了一种低复杂度基于脉冲调制的数据传输方案及优化方法。分别设计了基于脉冲位置调制及脉位结合极性调制的类语音信号,给出了基于跳时脉冲的帧同步方法。搭建了基于脉冲调制的GSM语音信道数据传输仿真平台,分析比较了不同调制阶数和不同自适应多速率编码 (AMR) 码率下系统的性能。为了提高系统可靠性,引入卷积码进一步降低了系统误码率。仿真结果表明,4阶脉冲调制最适用于语音信道,所提脉冲调制方法与传统低复杂度频移键控 (FSK) 调制方式误码率近似,但传输速率高,且提出的脉位结合极性调制进一步提高了传输速率,总提高比例达到36%。     

Rational Engineering of Multilayered Co3O4/ZnO Nanocatalysts through Chemical Transformations from Matryoshka‐Type ZIFs

Hybrid metal oxides with multilayered structures exhibit unique physical and chemical properties, particularly important to heterogeneous catalysis. However, regulations of morphology, spatial location, and shell numbers of the hybrid metal oxides still remain a challenge. Herein, binary Co₃O₄/ZnO nanocages with multilayered structures (up to eight layers) are prepared via chemical transformation from diverse Matryoshka‐type zeolitic imidazolate frameworks (ZIFs) via a straightforward and scalable calcination method. More importantly, the obtained ZIF‐derived metal oxides (ZDMOs) with versatile layer numbers exhibit remarkable catalytic activity for both gas‐phase CO oxidation and CO₂ hydrogenation reactions, which are directly related to the sophisticated shell numbers (i.e., Co₃O₄‐terminated layers or ZnO‐terminated layers). Particularly, in situ reflectance infrared Fourier transform spectroscopy (DRIFTS) results indicate that the promotional effects of the multilayered structures indeed exist in CO₂ hydrogenation, wherein the key reaction intermediates are quite different for five‐layer and six‐layer ZDMOs. For instance, *HCOO is the predominant intermediate over the six‐layer ZDMO; on the contrary, *H₃CO is the crucial species over the five‐layer ZDMO. The ZnO/Co₃O₄ interface should be the active sites for CO₂ hydrogenation to *HCOO and *H₃CO species, which are ultimately converted to the products (CH₄ or methanol). Accordingly, the work here provides a convenient way to facilely engineer multilayered Co₃O₄/ZnO nanocomposites with precisely controlled shell numbers for heterogeneous catalysis applications.