光脉冲在微环耦合谐振光波导中传输线性特性的数值仿真

利用传输矩阵法得到了微环耦合谐振光波导色散关系的一般表达式,并由色散关系出发讨论了光脉冲在微环耦合谐振光波导中传输时的线性特性,包括带宽、群速度、色散和线性相位变化,这些特性对微环耦合谐振光波导在光通信和光传感领域的应用有重要意义. 关键词： 微环光波导 光脉冲线性特性 传输矩阵法 数值仿真     

基于U型波导耦合单微环结构的高灵敏度湿度传感器

首次提出了一种基于U型波导耦合的新型单微环结构湿度传感器,该传感器以聚酰亚胺(polyimide,P1)作为感湿材料,当外界环境相对湿度变化时,引起感湿部位折射率的相应变化,导致传感器的输出光谱发生漂移。根据传输矩阵法推导U型波导耦合单微环结构的传递函数,重点讨论了不同感湿部位对输出光谱的影响,通过Matlab理论仿真,确定以U型波导耦合单微环结构整体作为最佳感湿部位。当U型波导的两个耦合点间的距离为微环周长的整数倍时,相比于传统的单微环结构,自由光谱范围(FSR)实现加倍。外界相对湿度从10%RH变化到100%RH时,传感器的输出光谱漂移量在0.027～0.191 μm之间变化,灵敏度高达0.001 8 μm/%RH,相比于具有高灵敏度的光纤光栅类湿度传感器,灵敏度提高了10~100倍,实现了在高灵敏度感湿的同时兼顾谐振峰两侧大范围的滤波选频。     

一种可调谐的单微环三耦合点的SOI微环滤波器

依据耦合模和传输矩阵理论,设计了一个新型单微环三耦合点的可调谐微环滤波器模型,并模拟仿真了输出端口的光谱特性。模型结构中,采用热光性质稳定的绝缘硅材料,通过改变反馈波导的长度和温度实现对输出光谱的分析与调制。仿真结果表明,当耦合系数k=0.018时,模型结构的自由光谱范围可近似认为达到43.8nm,品质因子可达1.25×105,作为滤波器保持了很窄的带宽,很高的品质因子和较大的自由光谱范围,得出通过改变反馈波导的温度或长度可实现特定谐振波长处滤波效果显著改善的结论,最后给出了相应的光谱曲线。     

耦合微环谐振腔光波导有限尺寸效应的优化

对耦合微环谐振腔光波导中的有限尺寸效应进行了研究.在CMROW两端引入抗反射结构,采用数值方法对抗反射中的三个交叉耦合系数进行了优化,消除了透射谱和群时延谱的有限尺寸效应.数值计算得到了弱耦合和强耦合情况下抗反射结构中优化交叉耦合系数的拟合公式,可以直接计算出消除有限尺寸效应时所需的优化参量.     

基于反谐振波导微环的光控波束延时网络设计

设计了面向Ka频段(30 GHz)相控阵天线的4阵元子阵集成波导光延时网络。该光延时网络采用相位调制方式将射频信号转换至光域,波导微环处于反谐振状态,以实现大带宽、连续可调延时;通过带通滤波仅对一个边带进行延时调控,基于差分平衡探测器还原出射频信号。优化设计了级联双波导微环的结构参数,使每条路径的延时量在0～24.9 ps范围内连续可调,延时带宽大于4 GHz,实现了最大扫描角为±30°的波束扫描。对光延时网络链路的增益和噪声系数进行了推导分析,评估了整个延时芯片系统在实际应用中的性能。     

一种适用于湿度传感的表面等离子微环传感器

提出了一种适用于湿度传感的表面等离子微环传感器。该传感器纵向上采用表面等离子多层波导结构,横向上采用U型微环结构,以聚酰亚胺(polyimide,PI)为感湿材料。根据传输矩阵法推导表面等离子微环传感器结构的传递函数,外界环境的相对湿度变化引起聚酰亚胺的折射率变化,从而多层波导结构的有效折射率发生改变,导致传感器的输出光谱发生漂移。重点分析讨论了多层波导结构的传输特性以及感湿部位折射率的变化对输出光谱的影响。根据计算和仿真得出：当U型波导的两个耦合点间的距离为微环周长的整数倍时,传感器的输出光谱水平漂移量较大,自由光谱范围(FSR)加倍,达到128 nm,当外界环境相对湿度从10%RH变化到100%RH时,漂移量Δλ_m在0.005～0.038 μm之间变化,相比于其他湿度传感器,灵敏度提高了10～50倍,高达0.0005 μm/%RH,并且传输稳定。结果表明：设计的表面等离子微环传感器,灵敏度较好,性能稳定,可以应用于湿度测量,并且实现了在高灵敏度感湿的同时兼顾大范围的滤波选频,为微型光学器件的制备提供了理论基础。     

自由光谱范围加倍的单微环谐振滤波器

基于两点耦合和光波干涉控制相移思想提出U型波导耦合单微环的谐振滤波器结构。利用传输矩阵法推导了此结构的数学模型,采用Matlab模拟了输出端口谱线形状。当微环与U型波导的两个耦合点之间的距离为微环周长的整数倍时,此新型微环谐振滤波器比传统的双直波导耦合单微环滤波器的自由光谱范围增加1倍。针对该结构参数,同时讨论了耦合系数对输出谱线的影响,得出当耦合系数为0.018时,输出谱线具有最佳的消光比,同时保持窄的带宽和高的品质因子。     

光在近耦合波导结构中的传输性质分析

从理论上讨论了光在两根相互耦合的波导中传播的性质，通过束传播法从数值模拟上对光在两根及三根相互耦合的波导中传播的特性进行了分析。得出光在两种近耦合波导结构中传输具有的特性分析结果。     

一维光子晶体微腔的光放大和耦合腔的滤波特性研究

用传输矩阵法(TMM)研究了由SiO2和TiO2组成的一维光子晶体微腔的放大特性和耦合腔光子晶体的滤波特性.结果表明:在微腔光子晶体的缺陷层中掺杂一定浓度的Er+3,则对中心波长λ0=1.532μm,可以实现光放大;而二耦合腔或三耦合腔光子晶体可以作为二波长或三波长的滤波片.     

Optical soliton with group delay in microring coupled-resonator optical waveguides

This paper derives the dispersion relation of microring coupled-resonator optical waveguides (CROWs) without any approximation by using the transfer matrix method. Based on the established dispersion relation of CROWs it obtains the slow group velocity and dispersion coefficient. It finds that the effect of dispersion on optical pulses can be adjusted to balance the effect of nonlinearity by changing coupling coefficient or loss, so optical soliton with group delay can be obtained in microring CROWs. The optical soliton with group delay is of great significance for applications of microring CROWs in delay lines and optical buffers of future all-optical communication systems.     

Transmission and group delay of microring coupled-resonator optical waveguides

We measured the transmission and group delay of microring coupled-resonator optical waveguides (CROWs). The CROWs consisted of 12 weakly coupled, microring resonators fabricated in optical polymers (PMMA on Cytop). The intrinsic quality factor of the resonators was 18,000 and the interresonator coupling was 1%, resulting in a delay of 110-140 ps and a slowing factor of 23-29 over a 17 GHz bandwidth.     

Propagation in a directional coupler of parallel microring coupled-resonator optical waveguides

The fundamental concept of coupled-resonator optical waveguides (CROWs) is for the first time taken a step farther to propose the more complicated case of coupled-resonator directional couplers, by analyzing the phenomenon of propagation in two parallel chains of microring resonators. Using the method of transfer matrices it is shown that the infinite coupler supports even and odd supermodes that satisfy frequency-shifted replicas of the familiar CROW dispersion equation as well as modified periodic Floquet conditions. Depending on the relative coupling strengths between neighboring resonators in the same chain and between the two chains, the frequency bands of the supermodes can overlap or be completely separated, resulting, in the latter case, to a complete bandgap around the central resonance frequency of the microrings. Three frequency windows, corresponding to totally different properties of directional coupling, are defined through this band-overlap mechanism along the increased total bandwidth of the coupler. These predictions are fully confirmed in the response of the realistic finite-length version of the considered coupler which is also analyzed.     

Calculation of cutoff frequency of arbitrary weak guidance optical waveguides by extended boundary condition method

The extended boundary condition method is applied to both circular and elliptical regions for calculating cutoff frequencies V_c of weakly guiding optical waveguides, which consist of a uniform cladding and a core with arbitrary shape and index profile. The frequency shift formula method is explained by means of the extended boundary condition method on circular regions. Comparing the method with analytic and other rigorous methods, we show that it is indeed a powerful tool. Numerical results confirm that the mode designation and arrangement order in elliptical and rectangular waveguides are, in general, dependent on the aspect ratio.     

光子晶体耦合腔波导的色散特性

理论研究表明，在基于光子晶体的耦合腔波导中，杂质带的色散性质取决于相邻缺陷间局域电磁场的特性，而非缺陷间距离的大小.在第一布里渊区中出现的杂质带的反常色散实际上是能带折叠的结果.通过计算结构的有效折射率，证实了杂质带色散是正常色散. 关键词： 光子晶体 反常色散 耦合腔 杂质带     

硅基槽式微环谐振腔型偏振解复用器全矢量分析

提出一种紧凑型偏振解复用器, 其中两条常规硅基波导作为输入/输出信号通道, 居于其中的槽式微环谐振腔用于偏振态/波长选择组件. 采用全矢量频域有限差分法详细分析了硅基常规及槽波导的模式特性, 结果发现其横磁模的模场布及其有效折射率相似, 而其横电模相应的特性则差异明显, 结果输入横磁模能够在谐振工作波长下从下路端口输出, 而输入横电模与微环耦合可以忽略, 直接从直通端口输出, 从而实现两偏振态的高效分离. 采用全矢量时域有限差分法详细分析了该偏振解复用器的光波传输特性, 结果表明, 当微环半径为3.489 μm时, 在1.55 μm工作波长下, 横磁模与横电模的消光比与插入损耗分别为 ～ 26.12 (36.67) dB与 ～ 0.49 (0.09) dB. 另外, 论文详细讨论了器件关键结构参数的制作容差, 并给出了输入模场在器件中的传输演变情况.     

金属包层渐变折射率介质光波导的传输特性与损耗

用金属包层介质光波导损耗的微扰理论及藉助多层近似法用递推公式分析渐变折射率波导传播常数的方法,对几种类型的金属包层渐变折射率介质光波导的传输特性与损耗进行分析和讨论,得到了与精确数值计算结果相吻合的结果.     

Rigorous analysis of optical forces between two dielectric planar waveguides immersed in dielectric fluid media

This work presents a rigorous analysis of optical forces between planar waveguides immersed in an arbitrary background medium. This approach exploits the Minkowski stress tensor formulation, which is compared with a normalized version of the dispersion relation method, showing excellent results agreement for different dielectric fluid media. Due to slot‐waveguide effect, optical forces from TM modes are more sensitive to changes in the fluid refractive index than the TE counterparts. Furthermore, the repulsive optical force from the antisymmetric TM1 mode becomes stronger for higher refractive indexes, whereas the attractive force of the symmetric TM0 mode becomes weaker. The methodology and results presented in this work provide a rigorous analysis of nano‐optomechanical devices actuated by optical forces in a broad range of materials and applications. Therefore, this study may impact areas of light‐induced interactions presenting novel optofluidic and optomechanical functionalities, thus finding applications in nanoscale transport, sensing and manipulation.

     

光波导等参元分析

本文提出一套用于分析任意介质光波导的等参元算法,它基于严格的E_z-H_z变分公式,采用八节点曲边四边形单元。这种类型的等参元分析法尤其适用于研究各种具有曲边边界的复杂光波导和光波导器件。作为例子,文中把这一方法用于分析阶跃型光纤,渐变型光纤、各向同性以及各向异性光纤耦合器。