Measurements of excess loss of the crossed waveguide using optical waveguide ring resonators

Crossed waveguide is widely used in optical devices, whose excess loss has a strong impact on multi-turn optical waveguide ring resonator and resonator integrated optic gyro. The resonance curve of the ring resonator is sharply dependent on the loss within the resonator. This paper presents how to get excess loss of the crossed waveguides nondestructively through the comparison of the resonance characteristics between one-turn and multi-turn optical waveguide ring resonators.     

On the orthogonality of the phase velocity and its feasibility for plane waves

Phase and group velocities of plane waves may have different directions in a linear and homogeneous medium. This difference may lead to interesting situations such as the phase reversal propagation and the orthogonal phase velocity. Although the former has been analyzed in depth and it has found many applications, the latter has been left as a hypothesis. Actually, due to our best knowledge there is no evidence of such media where the phase velocity is orthogonal to the group velocity. In this paper we discuss this situation thoroughly. We show that a plane wave with orthogonal phase velocity cannot possess linear momentum. Moreover, we show that a plane wave without the linear momentum cannot propagate at all, so the orthogonality of the phase velocity does not take place in reality for electromagnetic plane waves.     

强激光条件下5CB液晶中的激光诱导衍射环现象

强激光经5CB液晶传播时会产生非线性自相位调制现象,利用532 nm和1 064 nmCW激光研究了强激光条件下5CB液晶中的激光诱导衍射环现象,并对强激光在5CB液晶中产生自相位调制的现象和机理进行了讨论.当532 nm激光和1 064 nm激光功率密度分别大于10 kW/cm2和300W/cm2时,接收白屏上有较明...     

扶手椅型石墨烯介观环中的持续电流

在紧束缚近似下, 解析求解了扶手椅型边界石墨烯介观环的能量本征值问题, 计算和讨论了不同大小尺寸的介观环中持续电流随Aharonov-Bohm (A-B)磁通的变化, 并证明了能级和持续电流关于磁通变化的周期性和特殊对称性. 研究表明, 持续电流显著地依赖于介观环的几何结构; 零能量附近的能级可以承载较大的持续电流, 而远离零能量的其他能级对持续电流的贡献很小.     

带电细圆环与导体球壳系统的场分布

先依电象法,推导均匀带电圆环在金属导体球壳内的"象电荷";再在球坐标系下,根据电场强度的计算公式与Tay-lor展开式,计算出均匀带电细圆环在全空间的电场分布的级数形式解;进而结合唯一性定理和电场的叠加原理,获得带电细圆环与导体球壳系统的空间场分布.     

Coherence effect on decryption characteristics in message modulation type chaos secure communication systems using fiber-optic ring resonators

We numerically investigated the dependence of the decryption characteristics in a message modulation type chaos secure communication system using optical fiber ring resonators (OFRRs) on the coherence condition of carrier light. Since the output dynamics of OFRRs were formed on the basis of interference phenomenon among the circulated components in OFRRs, the coherence condition of input light affected inherently the OFRR output dynamics, resulting in the decryption characteristics. It was found that the decryption characteristics degraded as coherence length increased, i.e., as the spectral width of the input light decreased. The decryption characteristics also grew worse as the parameter differences between the transmitter and the receiver became larger.     

旋转调制捷联惯导激光陀螺仪误差自补偿新方法

基于旋转调制的自补偿技术是进一步提高激光陀螺仪捷联惯导系统导航精度的有效方法。研究了旋转调制捷联惯导系统中的激光陀螺仪误差补偿方法。建立旋转式捷联惯导系统激光陀螺仪的误差传播方程,分析激光陀螺仪旋转误差效应及误差传播特性,在此基础上建立了调制策略编排目标函数;研究了双轴交替旋转调制模式下的调制策略编排方案,提出了一种改进的16次序双轴交替旋转调制方法,建立了基于双轴转动角速度的动态误差方程,实现了转动过程中激光陀螺仪的常值项误差、标度因数误差、安装误差的有效补偿,进一步抑制速度误差积累所引起的位置误差。仿真结果验证了该方法的有效性,提高了捷联惯导系统导航精度,可为旋转调制光学捷联惯导系统设计提供理论参考。     

Origin of strain-induced resonances in flexible terahertz metamaterials

Two types of flexible terahertz metamaterials were fabricated on polyethylene naphthalate(PEN) substrates. The unit cell of one type consists of two identical split-ring resonators(SRRs) that are arranged face-to-face(i.e., Flex Meta F); the unit cell of the other type has nothing different but is arranged back-to-back(i.e., Flex Meta B). Flex Meta F and Flex Meta B illustrate the similar transmission dips under zero strain because the excitation of fundamental inductive–capacitive(LC)resonance is mainly dependent on the geometric structure of individual SRR. However, if a gradually variant strain is applied to bend Flex Meta F and Flex Meta B, the new resonant peaks appear: in the case of Flex Meta F, the peaks are located at the lower frequencies; in the case of Flex Meta B, the peaks appear at the frequencies adjacent to the LC resonance. The origin and evolution of strain-induced resonances are studied. The origin is ascribed to the detuning effect and the different responses to strain from Flex Meta F and Flex Meta B are associated with the coupling effect. These findings may improve the understanding on flexible terahertz metamaterials and benefit their applications in flexible or curved devices.     

δ势垒对多臂量子环中持续电流的影响

提出了含δ势垒的多臂量子环模型.研究发现总磁通为零时,持续电流随半导体环增大发生非周期性振荡,下臂因含δ势垒而获得最小的平均持续电流.AB磁通增强时,持续电流会发生周期性等幅振荡,并与电极的磁矩方向以及隧穿电子的自旋方向相关.两电极磁矩方向平行时,Rashba自旋轨道耦合具有改变持续电流相位和相位差的效应;两电极磁矩方向反平行时,Rashba自旋轨道耦合具有改变持续电流振幅的效应.各臂之间持续电流的不同与臂长和磁通分布的差异相关.在一定条件下,两种波函数所对应的持续电流是可分离的. 关键词： 多臂量子环 持续电流 δ势垒 Rashba自旋轨道耦合