Er3+:Yb3+共掺固体激光器的谐振腔设计及实验研究

考虑激光棒的热透镜效应对有源平平腔、平凹腔进行了数值计算,分析了谐振腔内激光光斑及腔体的稳定性.实验中以Er3+:Yb3+共掺磷酸盐玻璃为工作介质,成功地实现了平凹腔在常温下连续输出TEM00模的1.54μm激光,最大输出功率为21.5mW,光光转换效率达到了0.7%.     

传输同步辐射X射线的锥形单毛细管的物理特性

根据北京同步辐射装置生物大分子实验站(2W1A)的条件和应用,从理论上研究了锥形单毛细管传输同步辐射X射线的物理特性.计算了锥管传输效率随锥管长度、X射线能量的变化规律;计算了锥管出口处的光强分布,强度增益随工作距离的变化规律.结果表明:与传输发散X射线相比,锥形单毛细管传输平行X射线的物理特性有明显的不同.     

Experiment on 60-GHz MMW transmission performance in an optical fiber and wireless system

We experimentally investigate the transmission performance of 60-GHz signals over standard single-mode fiber (SSMF) and wireless links at different bit rates. Experimental results show that in a transmission of over 10-km SSMF and 1.3-m wireless link, bit rate reaches up to 5 Gb/s and bit error rate (BER) is less than 10 4 . The main limiting factor in such radio-over-fiber (ROF) systems is intersymbol interferences caused by the so-called walk-off effect when BER is below 10 8 . In addition, a transmission of over 20-km SSMF without chromatic dispersion compensation is briefly investigated. For a BER of 10 8 , the optical penalty is 2 dB.     

Transmission-mode GaN photocathode based on graded Al_xGa_(1-x)N buffer layer

We create a GaN photocathode based on graded Alx Ga1-x N buffer layers to overcome the influence of buffer-emission layer interface on the photoemission of transmission-mode GaN photocathodes.A gateshaped spectral response with a 260-nm starting wavelength and a 375-nm cut-off wavelength is obtained.Average quantum efficiency is 15% and short wavelength responses are almost equivalent to long wavelength ones.The fitted interface recombination velocity is 5×104 cm/s,with negligible magnitude,proving that the design of the graded buffer layers is efficient in obtaining good interface quality between the buffer and the emission layer.     

160-Gb/s polarization-multiplexing optical NRZ-DQPSK transmission using differential detection

Using differential detection,we perform polarization-multiplexing 160-Gb/s optical non-return-to-zero(NRZ) differential quadrature phase shift keying(DQPSK) signal transmission over 100-km standard single mode fiber at a bit error rate(BER) of less than 10-9.The enabling technology includes clock recovery,fine dispersion compensation,and polarization tracking for de-multiplexing.Furthermore,a hybrid clock recovery scheme is proposed.The scheme is realized with ordinary devices using an optoelectrical modula...     

The wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges

In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power flow in the finite plate are calculated by the Mindlin plate theory (MPT) and classic plate theory (CPT).To satisfy the boundary conditions and continuous conditions at the coupled junction of the finite L-shaped plate,the near-field and far-field waves are entirely contained in the wave approach.The in-plane longitudinal and shear waves are also considered.The results indicate that the vibratory power flow based on the MPT is different from that based on the CPT not only at high frequencies but also at low and medium frequencies.The influence of the plate thickness on the vibrational power flow is investigated.From the results it is seen that the shear and rotary inertia correction of the MPT can influence the active and reactive power at the junction of the L-shaped plate not only at high frequencies but also at low and medium frequencies.Furthermore,the effects of structural damping on the active and reactive power flow at the junction are also analyzed.     

土体水分传输的温度效应试验系统设计与应用

自制了一套用于研究温度作用下土体水分传输机制的室内试验模拟系统.采用水浴加热替代电阻丝直接加热的方案,解决加热不均匀且不容易控制温度的难题.应用串行通讯接口技术把智能温度控制仪表和微机连接,实现了温度自动控制和采集的自动化.开展了7组试验耗时接近1年,试验结果表明,该系统性能稳定、部件之间兼容性较好,连续工作30天温度...     

锂离子电池多孔电极理论的回顾与新思考

本文总结了Newman多孔电极理论的基本内容,提出若干改进思路. 提出基于离子-空穴耦合传输机制描述浓电解质中的离子输运过程,在此基础上引入离子-电子耦合转移反应的思想处理电极材料中的离子传输问题,并通过计算嵌锂材料的离子扩散系数验证其合理性. 总结了描述多孔电极多尺度结构的相关理论和技术,表明均质化方法和基于结构重建的介观模拟方法均能给出比较合理的有效输运参数,从而提高多孔电极理论模拟结果的准确性.     

六取代三环喹唑啉电荷传输性质的理论研究

六取代三环喹唑啉分子可以作为液晶半导体材料。使用电子传输的半经典模型和密度泛函理论方法在B3LYP/6-31G**水平上对六取代三环喹唑啉分子的电荷传输性质进行理论研究。结果显示,该分子的正电荷传输速率为负电荷传输速率的30倍。与苯并菲和六氮杂苯并菲比较,该分子更有利于正电荷传输。     

太赫兹波在一维反铁磁/电介质准周期光子晶体的传输性质

本文利用传递矩阵方法研究了电磁波倾斜入射时,一维反铁磁/电介质准周期光子晶体的透射性质.反铁磁层和电介质层按Fibonacci数列排列构成准周期光子晶体.通过数值模拟发现光子禁带中有透射峰出现, 而且随着准周期光子晶体级数的增加透射峰的数目也在增加.此外,透射峰受电介质层的介电常数、入射角度和电磁波偏振影响明显. 关键词： 反铁磁层 准周期光子晶体 太赫兹波传输性质