Photonic band gap from periodic structures containing anisotropic nonmagnetic left-handed metamaterial

<正>We demonstrate a photonic band gap(PBG) from one-dimensional(1D) periodic structures created by a double-layer unit cell with an air layer and an anisotropic nonmagnetic left-handed metamaterial(LHM) layer whose permittivity elements are partially negative.The requirements imposed on the materials and structures to realize a PBG are derived when the frequency is above or below the cutoff frequency,and the transmission properties of the PBG are discussed by utilizing 4×4 transfer-matrix method with dispersive semiconductor metamaterial.     

Output characteristic of Yb~(3+)-doped fiber laser at different temperatures

The output characteristics of Yb3 -doped fiber laser at different temperatures are investigated. When temperature is increased from 13 to 95℃, the center wavelength of laser changes from 1084.9 to 1096.3 nm, the output laser power decreases from 0.95 to 0.58 W, and the slope efficiency drops from 30.7% to 25.5%.     

高功率双包层光纤激光器受激拉曼散射和热效应的理论研究

 受激拉曼散射和热效应会限制光纤激光器功率的提高。利用高功率光纤激光器的速率方程和热传导方程，理论研究了双端泵浦和分布泵浦下双包层光纤激光器的受激拉曼散射和热效应，得到了光纤中的泵浦光、激光和斯托克斯光的功率分布，光纤激光器的输出特性以及光纤中的温度分布。分析表明，当泵浦功率增大到一定值时，光纤激光器中出现SRS，一部分激光功率会转移给斯托克斯光，影响激光功率进一步提高;与双端泵浦方式相比，分布泵浦下光纤激光器的斜率效率和最大输出功率相差不大，但是，光纤中的温度分布被有效地降低，因此，分布泵浦方式更为有效。     

端面泵浦掺Yb3+双包层光纤激光器

从双包层光纤激光器的速率方程出发，得到了光纤中泵浦光与激光的功率分布、输出功率与泵浦功率的关系、腔镜反射率及光纤长度对输出功率的影响。研究结果表明：输出激光功率与光纤长度及后腔镜反射率有很强的依赖关系，存在一个输出功率最大的最佳光纤长度。后腔镜反射率越大，输出激光功率越小；当光纤长度较短时，在输出端放置反射镜使泵浦光高反射，可以提高输出功率和效率。通过对端面泵浦掺Yb3+双包层光纤激光器进行理论分析和实验研究，得到输出激光的中心波长为1088.3nm，斜率效率为33.7%，最大输出功率为1.75W。     

半导体超常媒质矩形谐振腔(英文)

设计并研究了两个有不同各向异性参数的半导体超常媒质矩形谐振腔,其中填充了部分右手半导体超常媒质和部分左手半导体超常媒质。通过作图法研究了充满非色散的右手半导体超常媒质和色散的左手半导体超常媒质的谐振腔中谐振模式的解。结果显示,谐振腔的谐振模式取决于半导体超常媒质的色散关系。讨论了每种谐振腔中包含的六种情况,分别表示两个区域的传播常数为实数和虚数的不同的组合,并且揭示了构建具有无相差特性的谐振腔的几何参数要求。     

单点侧向泵浦掺Yb3＋双包层光纤激光器理论研究

 从速率方程出发，建立了单点侧向泵浦掺Yb³⁺双包层光纤激光器的理论模型并进行了数值分析，得到了泵浦光方向分别为正向、反向、双向时,光纤内泵浦光和激光功率的分布特性及输出功率与泵浦点位置的变化关系。结果表明，相对于泵浦光正向或反向传输，当泵浦光双向传输时，光纤中的激光功率分布和输出激光功率受泵浦点的位置影响较小，对于侧向泵浦的双包层光纤激光器是较好的选择。     

伺服加速度计用于倾角测量的抗振动实验研究

针对伺服加速度计在振动状态下倾角传感测量出现偏差的问题，采用了两种减振方案来减少这个测量偏差。实验研究表明，使用软性发泡材料减振是一种行之有效的方法。     

Integrated optical electric field sensor with telescopic dipole

An integrated optical electric field sensor based on a Mach-Zehnder interferometer with the telescopic dipole is designed and fabricated, and its electrodes are segmented and connected with a telescopic dipole. The measured results show that when the frequency response is from 10 kHz to 6 GHz with the antenna length of 55 mm, the minimum detectable electric field of 20 mV/m can be obtained, and the linear dynamics range can reach 90 dB at 250 MHz.     

Optical E-field probe using LiNbO_3 M-Z waveguides in the electromagnetic compatibility measurements

An integrated optical E-field probe with the segmented electrode using LiNbO3 Mach-Zehnder (M-Z) waveguides is proposed and an equivalent circuit of the segmented electrode is given. According to the circuit theory, the electrode structure of the probe is designed. The unpackaged size of the fabricated probe is as small as 60×6×0.5 (mm). The measured results show that the half wavelength voltage is 7.7 V, the±5 dB baseband range is 3 GHz, and the minimum detectable field is lower than 90 dB·μV/m (bandwidth 100 Hz). Therefore it can be used in the electromagnetic compatibility (EMC) measurements.     

Bend effect of the electrode for travelling wave integrated electro-optic modulators

In this paper, we have studied electrode bend effects on electrical characteristics of the modulator in the three aspects, which are arc length, characteristic impedance, and loss, applying the model in Ref. [1] and the finite element method (FEM). The results have shown that the effect only caused by the characteristic impedance is necessarily considered while its deviation is large, but others are negligible as we design a practical device. Finally, some transmission characteristics of coplanar line with different arc length of the bend have been tested, and the measured results are in good agreement with the theoretical analyses.