MIM表面等离子激元布拉格纳米微腔

构建了一种金属-绝缘体-金属(MIM)表面等离子体布拉格波导结构,绝缘层为一维布拉格光栅结构。在布拉格光栅结构中引入缺陷,形成布拉格纳米微腔。这种纳米微腔结构可以将光子能量很好地局域在微腔中,且在金属与绝缘层界面上光子能量最强。分析了MIM波导的色散特性,获得了谐振波长为1550 nm时微腔的结构参数。同时利用时域有限差分(FDTD)方法讨论了绝缘层布拉格光栅周期数、绝缘层厚度、微腔长度对微腔品质因子Q和模式体积V的影响。通过合理的选择这些参数可以提高微腔性能,使其具有极小的模式体积V和高的Q/V值,可实现光子局域化。     

波导耦合多层结构光学微球腔性能分析

利用时域有限差分(FDTD)法模拟了均匀结构、双层结构和三层结构光学微球腔,得到了各自的能量密度分布,通过对比发现多层结构具有更高的最大能量密度与存储能量和较小的模式体积。波导与多层微球腔之间存在一个最佳间隙,模拟结构的最佳间隙在60～120nm。改变高折射层的厚度和折射率,在特定波长的入射光下可以获得具有较高最大能量密度(大于360)或者较小模式体积的(小于0.03)的微球腔,确定了优化的厚度和折射率。分析高斯光激励的带有导出波导的微球腔,导出波导与微球腔中的光具有相似的激发频谱,表明多层微球腔可以对入射光实现选频并导出。结果显示,多层微球腔具有更好的性能,为光学微球腔后续的结构设计和实际应用提供了一个新的优化思路。     

聚合物光波导的模场特性分析

用时域有限差分法(Finite Difference Time-Domain,FDTD)对电光聚合物脊形波导进行了模拟分析,通过改变脊形波导的结构参数(脊高、脊宽、脊高比)来观察波导内的模场分布特性、对模式数量的影响.获得了通过调整脊宽和脊高比等参数,设计单模电光聚合物脊形波导的条件.同时验证了采用FDTD数值算法可以比较精确地模拟计算光波导器件性能.     

三维半导体GaAs量子阱微腔中的腔极化激元

半导体微腔中腔模和激子模耦合形成腔极化激元,三维微腔中由于横向限定腔模和激子模形成离散化的本征模式.本文计算了远离截止近似下,三维半导体微腔中空腔腔模的能量与微腔半径的关系;及腔模和激子模耦合后,三维半导体柱型微腔中具有相同角量子数和径向量子数的两个低阶腔模、重空穴激子模、轻空穴激子模耦合形成的腔极化激元能量随微腔半径变化的情况.结果表明随着微腔半径的减小腔模能量蓝移,腔模与相应的重空穴激子模、轻空穴激子模耦合形成的腔极化激元的三支随着微腔半径的减小存在明显的反交叉行为.随着微腔半径的变化,极化激元的三支所体现的模式的特性是变化的.     

红光GaInP/AlGaInP正方形微腔激光器

利用普通光刻和感应耦合等离子体(ICP)刻蚀技术制作了红光GaInP/AlGaInP正方形微腔激光器,光功率电流曲线表明,器件实现了200 K的低温激射。对边长为10μm、输出波导长为30μm的正方形微腔激光器,室温测量得到的纵模模式间距为1.3 nm,所对应的是由输出波导和正方形腔组成的F-P腔的F-P模式。采用二维时域有限差分法(FDTD),模拟研究了侧壁粗糙对正方形腔模式品质因子的影响。     

波导耦合回音壁模式光学微球腔结构耦合特性分析

提出了一种耦合微球和波导系统的有效方法,并在数值和实验上进行了论证.为了研究微球腔和波导系统的耦合特性,首先通过耦合模理论研究了这个系统的2D模型.通过有限时域差分法设计了一个数值仿真系统.在快速傅里叶变换(FFT)处理样本数据后,得到了波长范围从600 nm到1 000 nm的相对强度谱曲线和传输谱曲线.在实验中,采用熔融单模光纤顶端的方法制得了石英材料微球腔.采用热拉技术制得了锥形光纤,用来作为激发微球腔中回音壁模式的波导.测试了这个微球腔-锥形光纤耦合系统,通过优化微球腔与锥形光纤的相对位置得到其品质因数高达2.3×106,耦合效率高达92.5%.这些耦合特性可以很好地用理论结果解释.这些特性表明了其在实际微腔传感和微型激光器中极具潜力.     

分布布拉格反射器(DBR)对半导体微腔一些特性的影响

从光学传输矩阵方法出发,研究了分布布拉格反射器(DBR)生长顺序的不同对半导体平面微腔中电场振幅极大值位置及整个微腔选频特性的影响;同时指出了DBR对于λ0/2和λ0腔不同情况的最佳生长模式.     

相位调制对高Q光学微球腔谐振特性的影响

光学微腔由于其极高的品质因数(Q)特性而具有广泛的应用前景。该文根据光学微球腔与锥形光纤的耦合原理对光学微球腔的谐振特性进行了实验研究。通过实验研究了相位调制参数对光学微球腔谐振深度的影响,并获得了相位调制电压和调制频率与光学微球腔谐振深度变化的关系。实验结果表明,相位调制参数的变化,对光学微球腔的谐振特性——谐振深度,有一定影响,在应用中根据需要选择合适的相位调制参数。     

相位调制对高Q光学微球腔谐振特性的影响

光学微腔由于其极高的品质因数(Q)特性而具有广泛的应用前景。该文根据光学微球腔与锥形光纤的耦合原理对光学微球腔的谐振特性进行了实验研究。通过实验研究了相位调制参数对光学微球腔谐振深度的影响,并获得了相位调制电压和调制频率与光学微球腔谐振深度变化的关系。实验结果表明,相位调制参数的变化,对光学微球腔的谐振特性——谐振深度,有一定影响,在应用中根据需要选择合适的相位调制参数。     

分布布拉格反射器(DBR)对半导体微腔一些特性的影响

从光学传输矩阵方法出发 ,研究了分布布拉格反射器 (DBR)生长顺序的不同对半导体平面微腔中电场振幅极大值位置及整个微腔选频特性的影响 ;同时指出了 DBR对于λ0 / 2和λ0 腔不同情况的最佳生长模式     

A study of the nonorthogonal FDTD method versus the conventionalFDTD technique for computing resonant frequencies of cylindricalcavities

The nonorthogonal finite-difference-time-domain (FDTD) technique is used to compute the resonant frequencies of dielectric-filled cylindrical cavities. Because the method is based on the nonorthogonal coordinate system, it is not restricted to specific geometries, e.g. rectangular or axially symmetric geometries, and is suitable for analyzing cavities of arbitrary shape. The advantages of this technique over the conventional FDTD algorithm with a staircase grid are shown in a convergence study, where the two methods are used to compute the dominant resonant frequency of a cylindrical cavity. The accuracy of the technique for calculating the resonant frequencies of the first few modes is demonstrated by comparing the results obtained with this technique with those derived by using two versions of the finite element method in the frequency domain     

Theoretical modeling of cavity-backed patch antennas using a hybridtechnique

A hybrid technique that combines the method of moments (MoM) and the finite element method (FEM) to analyze cavity-backed patch antennas is presented. This technique features the use of FEM in solving the electromagnetic field distribution in the cavity and the use of MoM in solving integral equations outside the cavity. The results of MoM and FEM are combined through the continuity conditions on the boundary of the cavity. Due to the flexibility of FEM, complex cavities filled with inhomogeneous media can be analyzed by this technique. The results obtained by this hybrid technique are compared to the finite difference time domain (FDTD) results and good agreement is found     

Analysis of modes in a free-standing nanowire cavity by FDTD simulation

The mode frequency and the quality factor of nanowire cavities are calculated for the intensity spectrum obtained by the finite-difference time-domain （FDTD） technique and the Pade approximation. In the free-standing nanowire cavity with the dielectric constant ε=6.0 and the length of 5μm, the quality factors of 130,159,and 151 are obtained for modes with frequency around 798 THz,at the cavity radius of 60 nm, 75 nm, and 90 nm, respectively. The obtained field distribution of the fundamental transverse mode shows that the mode field is confined very well by the nanowire cavity even when the radius of nanowire is much smaller than the mode wavelength.     

Analysis of mode characteristics for deformed square resonators by FDTD technique

The mode frequencies and quality factors (Q-factors) in two-dimensional (2-D) deformed square resonators are analyzed by finite-difference time-domain (FDTD) technique. The results show that the deformed square cavities with circular and cut corners have larger Q-factors than the perfect ones at certain conditions. For a square cavity with side length of 2 /spl mu/m and refractive index of 3.2, the mode Q-factor can increase 13 times as the perfect corners are replaced by a quarter of circle with radius of 0.3 /spl mu/m. Furthermore the blue shift with the increasing deformations is found as a result of the reduction in effective resonator area. In square cavities with periodic roughness at sidewalls which maintains the symmetry of the square, the Q-factors of the whispering gallery (WG)-like modes are still one order of magnitude larger that those of non-WG-like modes. However, the Q-factors of these two types of modes are of the same order in the square cavity with random roughness. We also find that the rectangular and rhombic deformation largely reduce the Q -factors with the increasing offset and cause the splitting of the doubly degenerate modes due to the breaking of certain symmetry properties.     

电大尺寸复杂结构腔体电磁散射的IPO/FEM混合法研究

该文将物理光学迭代法(IPO)的子域连接法与矢量有限元法(FEM)相结合,提出了一种新的混合方法用于分析计算电大尺寸复杂结构腔体目标的电磁散射特性。对于腔体内部适合用高频方法处理的部分采用IPO方法分析;对于具有复杂结构和材料特性的部分,采用矢量有限元法进行研究,利用交界面上的连续性条件实现这两种方法的耦合。为了验证理论模型的正确性,该文对某一矩形空腔及底部加载金属台阶的腔体进行了分析,计算结果与文献数据以及用时域有限差分法所得结果一致,并具有很好的收敛效果。在此基础上,对底部加载介质层的复杂结构腔体进行了分析计算,结果表明这种混合方法对于分析电大尺寸复杂结构腔体的散射特性是行之有效的。     

Computation of resonant frequencies and quality factors of cavitiesby FDTD technique and Pade approximation

The finite-difference time domain (FDTD) technique and the Pade approximation with Baker's algorithm are used to calculate the mode frequencies and quality factors of cavities. Comparing with the fast Fourier transformation/Pade method, we find that the Pade approximation and the Baker's algorithm can obtain exact resonant frequencies and quality factors based on a much shorter time record of the FDTD output     

Fast Calculation of Cavity-Mode Characteristics of Photonic Crystal Cavities

A fast approach based on effective index perturbation method is proposed to evaluate the intrinsic characteristics of photonic-crystal-slab-based microcavity with two-dimensional finite-difference time-domain (2-D FDTD) technique. For two widely used single defect structures, less than 2% computational error was obtained in calculating the defect mode frequencies. Accurate prediction of cavity modal properties and resonant peak frequencies is feasible based on 2-D FDTD simulation by adjusting the effective index to match the dielectric band edge for donor-like defect mode. The correlation between the modified effective index and the cavity (lasing) mode with the highest quality factor$Q$offers an efficient tool in the design of defect mode based photonic crystal microcavities.     

Analysis of mode quality factors and mode reflectivities for nanowire cavity by FDTD technique

The mode frequency and the quality factor of nanowire cavities are calculated from the intensity spectrum obtained by the finite-difference time-domain (FDTD) technique and the Pade/spl acute/ approximation. In a free-standing nanowire cavity with dielectric constant /spl epsiv/=6.0 and a length of 5 /spl mu/m, quality factors of 130, 159, and 151 are obtained for the HE/sub 11/ modes with a wavelength around 375 nm, at cavity radius of 60, 75, and 90 nm, respectively. The corresponding quality factors reduce to 78, 94, and 86 for a nanowire cavity standing on a sapphire substrate with a refractive index of 1.8. The mode quality factors are also calculated for the TE/sub 01/ and TM/sub 01/ modes, and the mode reflectivities are calculated from the mode quality factors.     

应用FDTD/MP方法计算波导加载谐振器的复谐振频率

应用FDTD结合MP的方法计算了波导加载谐振器的谐振频率和品质因数。与FDTD/DFT方法比较,这种方法减少了对FDTD运行时间的需求,并且提高了数值精度。与FDTD/Prony方法比较,其优点是计算效率高,对噪声的敏感小。文中以计算实例说明了算法的有效性。     

基于对称型齿波导和纳米盘的类EIT和慢光效应

设计了一种新型的基于金属表面等离子体激元（SPPs）的亚波长金属-绝缘体-金属（MIM）型类电磁诱导透明（EIT）系统,该系统由一个直波导及其两边对称的齿形腔和纳米盘耦合而成。利用耦合模式理论对结构进行分析,并通过时域有限差分方法（FDTD）进行数值模拟。当齿形腔和纳米盘的共振频率相近,可以获得类EIT效应,改变齿形腔的长度和纳米盘的半径可以调节透明窗的位置。该装置可以用作高性能的类EIT滤波器,透过率高达77.5%,半高宽低至35.5 nm,群指数高达65,为高度集成光网络提供了一种新的方法,可应用于波长选择器、超快开关、光存储等设备。