Archimedes 32,4,3,4结构光子晶体中与偏振无关的自准直分束器

通过等频图分析并结合时域有限差分法法模拟, 在Archimedes 3²,4,3,4结构排列的二维光子晶体中同一频率下同时实现了电磁波两种偏振态的自准直. 研究发现,在该结构光子晶体中引入缺陷,当线缺陷宽度改变时, TE和TM两种偏振态光束的分束效果将会随之变化.由此通过控制缺陷宽度,分别实现了两种偏振态光束的50% ∶50%分束以及90°大角度光折弯,分束和折弯的效率都较为理想,为未来设计基于光子晶体的新型光子学器件提供了一种新的思路.     

基于光子晶体自准直和带隙效应的马赫-曾德尔干涉仪设计

结合能带图和等频图分析,基于光子晶体自准直和光子带隙效应,设计了一种紧凑、高效的全光子晶体马赫-曾德尔(MZ)干涉仪.相应的光分束器和反射镜均由缺陷结构的光子晶体实现.讨论了干涉仪的输出机理,并与时域有限差分法(FDTD)模拟结果进行了比较.结果分析表明可以把MZ干涉仪作为一种气体、液体微型探测器.可在集成光学中起到重要的作用. 关键词： 光子晶体 自准直 MZ干涉仪     

Polarization-independent linear waveguides in 3D photonic crystals

Using a symmetry-based approach, we have designed polarization-independent waveguides in a 3D photonic crystal. A comprehensive series of numerical experiments, involving the propagation of pulsed signals through long straight waveguide sections and sharp bends, quantitatively evaluates the bend-transmission coefficient over the entire bandwidth of the corresponding guided modes. High (approximately 95%) polarization-independent bend transmission is achieved within a certain frequency range.     

Arbitrary angle waveguide bends in two-dimensional photonic crystals

Arbitrary angle waveguide bends in two-dimensional photonic crystals are studied with modeling and calculation. The lattice orientation restriction to bending angles can be avoided by incorporating an annular air groove into the bending corner. Theoretical analysis shows that the sharp bends transmit guided lightwaves with a very slight difference of propagation properties between straight waveguides and bend sections. A transmission of larger than 90% with a bandwidth of wider than 52 nm is obtained in the vicinity of 1.55 μm for the sharp bends with bending angles from 0° to 165°.     

Line defect splitters for self-collimated beams in photonic crystals

A one-to-two splitter for self-collimated beams in photonic crystal (PC) is designed by inserting one row of line defects. Finite-difference time-domain (FDTD) method is used to simulate the light propagation process. Our systematical studies show that the splitting ratio is a function of the airholes size of the line defect radius, and stays fairly constant as a function of frequency. Furthermore, it is shown the numerical results can be analyzed by coupled-mode theory.     

Polarization-independent beam splitting by a photonic crystal right prism

Splitting of light waves by a two-dimensional photonic crystal associated with source size and dispersion relation of photonic crystal at a wavelength of 1,550 nm without disturbing periodicity is numerically demonstrated via finite-difference time-domain simulations. Split branches in either polarization state make plus or minus 45° with the [11] direction and propagate in a self-collimated manner with equal amplitude and phase. Sixty-four percent of total transmittance is attained provided that the waves are coupled and collected through appropriate planar waveguides. Alternatively, approximately 50 % total transmittance for both polarizations can be obtained by application of an anti-reflection coating layer at the input face. Polarization-independent beam splitting occurs in a narrow range around the target wavelength, while its transverse-magnetically polarized sub-harmonic can also be split. The photonic crystal can also operate as a polarizing splitter at oblique incidence.     

Design and fabrication of high-efficiency photonic crystal power beam splitters

Efficient beam splitters in a planar photonic crystal waveguide with corrugated terminators were designed, fabricated, and characterized. Experimental results showed that these beam splitters have high splitting efficiency and power intensity in the propagation direction, an achievement made possible through a design method employing a genetic algorithm-based optimization method. High-efficiency power beam splitters are useful components in integrated optics, and the design implemented here is particularly suited for integration with other optical components.     

Polarization-independent rapidly tunable optical add-drop multiplexer utilizing non-polarizing beam splitters in Ti:LiNbO3

A polarization-independent four-port wavelength-tunable optical add drop multiplexer (OADM) that utilizes non-polarizing relaxed beam splitters has been analyzed and demonstrated in Ti:LiNbO₃ at the 1530 nm wavelength regime. The design utilizes an asymmetric interferometer configuration with strain induced index grating for polarization coupling along its arms that are shifted in position relative to each other. Experimental results of the filter response agree with theoretical predictions. Electrooptic tuning over a range of 15.7 nm at a rate of 0.08 nm/V has been measured. A temporal response < 46 ns to a 20 V step change in tuning voltage has been demonstrated. Fiber-to-fiber insertion loss is ~ 6.5 dB.     

含负折射率材料1维光子晶体的偏振无关非全向的缺陷模

运用光学传输矩阵理论,研究了含负折射率材料1维光子晶体缺陷模的偏振特性。结果显示,零均折射率带隙中缺陷模对入射角和偏振有较强的依赖。通过对缺陷层参数的优化设计,得到了一系列的偏振无关非全向缺陷模,这是传统1维光子晶体中不能出现的。应用这些缺陷模,设计了低通、高通、带通空间滤波器。与传统光子晶体空间滤波器相比,这些空间滤波器具有偏振无关的优点。     

Dispersion-based beam splitter in photonic crystals

A novel implementation of a dispersion-based beam splitter in a photonic crystal (PhC) is proposed. The beam splitter consists of two periodic structures: a nonchannel dispersion-guiding region and a splitting structure operating inside the photonic bandgap. The dispersion-guiding PhC structure is used to route the optical wave by exploiting the dispersion properties of the lattice. An arbitrary power ratio between the output beams can be achieved by varying the parameters of the splitting structure. Within the studied range of splitting structures, high output power was observed and verified experimentally.     

含负折射率材料1维光子晶体的偏振无关非全向的缺陷模

运用光学传输矩阵理论,研究了含负折射率材料1维光子晶体缺陷模的偏振特性。结果显示,零均折射率带隙中缺陷模对入射角和偏振有较强的依赖。通过对缺陷层参数的优化设计,得到了一系列的偏振无关非全向缺陷模,这是传统1维光子晶体中不能出现的。应用这些缺陷模,设计了低通、高通、带通空间滤波器。与传统光子晶体空间滤波器相比,这些空间滤波器具有偏振无关的优点。     

Design of photonic crystal power beam splitters via corrugated and gratinglike surfaces

In this work, we use the finite-difference time-domain method in conjunction with a genetic algorithm to design photonic crystal power beam splitters based upon a typical planar photonic crystal waveguide with corrugated surfaces or gratinglike surfaces covered behind the termination. Considering a power detector placed at different locations in the output field, we have obtained several beam splitters designs with different splitting angles. These beam splitters have high splitting efficiency and power intensity in the propagation direction.     

Self-collimation and beam splitting in low-index photonic crystals

We study self-collimation and beam splitting in low-refractive-index photonic crystals created within chalcogenide glass. We propose a beam splitter structure that allows direct experimental verification of photonic-crystal effects at optical wavelengths in a straightforward and definitive manner. The beam splitter provides angular separation of 90° using a highly compact spatial footprint, thus delivering direct application in highly integrated photonic devices.     

Polarization beam splitters based on a two-dimensional photonic crystal of negative refraction

A two-dimensional metallo-dielectric photonic crystal of negative refraction was designed for the application of polarization beam splitters. To match the refractive index of air, the effective refractive index of the designed photonic crystal is -1 for TE polarization and +1 for TM polarization. Two types of polarization beam splitter are presented.     

光子晶体自准直光束偏振分束器

结合能带图和等频图分析,基于光子晶体自准直效应和光子带隙,设计了一种紧凑、高效的偏振分束器.时域有限差分法(FDTD)模拟表明,该设计可以在一个较大的频率范围f=0.268—0.278(c/a) 内实现TE模和TM模的高效(85%)、大角度(90°)分离.在光通讯波长λ=1.55 μm,该设计尺寸仅为9 μm×9 μm.这些特性使其在光通讯领域中具有重要的应用前景. 关键词： 光子晶体 偏振分束器 自准直     

All-optical analog-to-digital converters based on cascaded 3-dB power splitters in 2D photonic crystals

In this paper, a new design of a photonic crystal (PC) all-optical analog-to-digital converter (ADC), which is based on cascaded 3-dB power splitters, is presented. It has been shown that by choosing appropriate threshold values in the output ports of the 3-dB power splitters, a set of unique states corresponding to different power levels of input analog signal can be obtained. It has been demonstrated that based on the proposed approach, the design of 2 and 3-bit PC ADC can be achievable.     

Photonic crystal bends and power splitters based on ring resonators

In this paper, theoretical and numerical analysis of low-loss right angle waveguide bends and T-junctions based on ultra-compact photonic crystal ring resonators (PCRR) is presented. Desirable characteristics are obtained by designing the waveguide bends and T-junctions as low-Q resonant cavities with certain symmetries and small radiation loss. A simple analysis, based on coupled mode theory (CMT) in time, is used to explain the operation principles which agree qualitatively with the numerical results. These structures have high transmission efficiency over a large bandwidth in third communication window. Also effects of changing the ring size on power splitter transmission characteristics are discussed. The perfect transmission and zero reflection conditions are discussed by applying coupled mode theory. Results obtained by the finite difference time domain (FDTD) simulations are consistent with those from the coupled mode theory.     

Photonic crystal beam splitters

In this work, the beam splitter with two input ports and two output ports in two-dimensional photonic crystals is studied through the finite-difference time-domain method. The beam splitter consists of two orthogonally cross line defects. The diameter of the two diagonal air holes at the intersection of the two line defects was modified. The input light can be identically divided into the two output ports. The beam splitters can be applied in the photonic crystal Mach-Zehnder interferometers or photonic crystal optical switches.     

Detailed investigation of self-imaging in multimode photonic crystal waveguides for applications in power and polarization beam splitters

Properties of the self-imaging effect based on multimode interference (MMI) in multimode photonic crystal waveguides (PCWs) are investigated and analyzed in detail. By combining photonic band gap (PBG) and total internal reflection (TIR) effects in PCWs, self-imaging phenomena are achieved for both TE and TM polarizations. To observe the images reproduced by this self-imaging phenomenon, finite-difference time-domain (FDTD) simulations are performed on a multi-mode PCW. From these numerical simulations the reproduced images are identified and their positions along the propagation axis are described. We also, present the design and simulation of novel polarization-insensitive power splitter and polarization splitter. The simulation results show that the optimized devices have excellent transmission efficiencies as well as wide operating frequency bandwidths and small structure size. So, the proposed devices are promising and may play an important role in high-density photonic integrated circuits in the future.