Guiding of a one-dimensional optical beam with nanometer diameter

The concept of a one-dimensional optical wave and its waveguides are proposed for what is to our knowledge the first time. The proposed waveguides are principally new and named for one-dimensional optical waveguides. One-dimensional optical waveguides make it possible to guide very thin optical beams in the visible or the near-infrared region with a diameter in the nanometer range. The propagation properties are analyzed theoretically. The applications of the waveguides to optical devices in the nanometer range are discussed.     

Packing density of conventional waveguides and photonic crystal waveguides

We compare coupling between parallel waveguides within one-dimensional photonic crystals and coupling between conventional waveguides. We consider the situation in which coupling between the waveguides is minimized, so that light in the waveguides propagates essentially independently. Subject to this condition, we compare the minimum mutual distance between conventional planar waveguides and waveguides in one-dimensional photonic crystals. We find that the packing densities of the conventional and periodic structures are comparable.     

Reducing crosstalk between nanowire-based hybrid plasmonic waveguides

Hybrid plasmonic waveguides based on a surface oxidized dielectric nanowire placed on a metal surface can facilitate simultaneously deep subwavelength mode confinement and large propagation length. Directional coupling based on such waveguides are theoretically investigated. Much lower crosstalk is noticed for such hybrid plasmonic waveguides compared to conventional waveguides based on bare dielectric nanowires. Some modifications, such as vertically placing the metal surfaces or using a metallic block between the nanowires, are studied which can further reduce the crosstalk between two waveguides. The proposed low crosstalk structures based on hybrid plasmonic waveguides can provide a simple platform for plasmonic integration which can at the same time easily interface with traditional photonic circuits.     

小尺寸低折射率差硅基二氧化硅阵列波导光栅

随着AWG型器件在光通信系统中的大规模应用,对低成本AWG芯片的需求越来越多。在各种降成本方案中,减小AWG芯片的尺寸是最有效的方法之一。本文介绍了一种新型小尺寸低折射率差硅基二氧化硅阵列波导光栅（AWG）的设计。在该AWG中,输入波导/输出波导与平板波导连接的部分制作成两侧为空气槽的高折射率差波导,所以在与输出平板波导连接处的相邻输出波导间距较小,这样可以在设计上缩短平板波导的长度、减少阵列波导的数量,实现较小的AWG芯片尺寸。该AWG的其它部分,如输入/输出波导与光纤耦合的部分、阵列波导光栅等均采用常规的低折射率波导工艺,所以就同时具有与常规的低折射率波导AWG相同的优点：如低耦合损耗、较好的串扰以及光学特性等。根据这个原理,设计了一种40通道100 GHz频率间隔的低折射率差硅基二氧化硅AWG,其芯片尺寸只有23.88 mm?10.5 mm,是传统相同材料制作的AWG尺寸的1/6。     

弯曲波导之间的耦合分析

采用极坐标下的光束传播法分析了两条平行变曲波导的中心间距、曲率半径等因素对模式耦合的影响,得到了耦合长度、耦合强度随中心间距、曲率半径的变化规律,并将直波导作为变曲波导的一种特殊情况进行了分析.     

Optical propagation of the HE11 mode and Gaussian beams in hollow circular waveguides

The propagation of the HE₁₁ mode and Gaussian beams in hollow oversized circular waveguides is analyzed using optical theories. Different types of waveguides are considered : hollow dielectric or conducting waveguides, dielectric-lined waveguides, corrugated waveguides. General formulas are derived which give the power transmission through these different guides. The best wall materials and structures are determined from a comparison of the waveguide transmissions, at the infrared and millimeter wavelengths. The question of the coupling between the HE₁₁ mode and Gaussian beams is discussed and from a review of coupling coefficients derived before, an optimum value is pointed out. The problem of matching a Gaussian beam into circular waveguides in order to achieve the maximum power transmission is analyzed. These results are of interest for infrared lasers or waveguide applications and for Electron Cyclotron Wave (ECW) systems at the millimeter wavelength.     

四种非矩形截面传感波导中的TE波和TM波

用保角变换将非矩形截面传感波导变换成等效矩形截面波导．给出计算等效矩形截面波导的TE模和TM模、电磁场、临界频率、波导壁电流、功率传输和衰减的公式．并给出4种非矩形传感截面波导数值计算的例子．     

Modes of UV-written planar waveguides

The UV-induced refractive-index increase in photosensitive planar waveguides is modeled by an exponential profile. Closed-form field solutions are given and dispersion curves are calculated for TE and TM modes. Modes in air-covered waveguides can be less sensitive to the UV-written profile than modes in buried waveguides.     

硅基混合表面等离子体纳米光波导及集成器件

总结并展望了硅基混合表面等离子体纳米光波导及集成器件方面的理论和实验研究工作。首先介绍了几种硅基混合表面等离子体纳米光波导结构,其尺寸可小至100 nm以下,而传播长度达100μm量级;其次介绍了基于硅基混合表面等离子体纳米光波导的功分器、偏振分束器和谐振器等集成器件,其尺寸为亚微米量级;最后探讨了硅基混合表面等离子体纳米光波导与硅纳米线光波导的耦合及对其进行增益补偿。     

Small-bore fluorocarbon polymer-coated silver hollow glass waveguides for Er:YAG laser light

Several types of fluorocarbon polymer (FCP)-coated silver hollow glass waveguides have been fabricated for Er:YAG laser delivery by using the improved wet chemical technique and dynamic coating procedure. The straight losses of 2 m long 700 μmØ and 540 μmØ waveguides are 0.4 and 1.0 dB, respectively. The transmission losses of these waveguides are below 1.5 dB even when the waveguides are bent to 180° with the bending radius of either 20 or 15 cm. The waveguides with the small diameters of 320 and 200 μm have also been developed for clinical treatment, which exhibit low enough transmission losses for Er:YAG laser light.     

硅基脊型波导器件过渡区损耗及偏振效应

在绝缘层上的硅材料上制作了四种具有不同输入输出结构的星形耦合器并进行了测试,对脊形波导与平板波导相互过渡时过渡区的损耗问题进行了研究和讨论,计算得到在所使用的材料参量下利用锥形结构可以得到1dB左右的最小损耗,这一损耗是由于脊型波导与平板波导间的模式失配造成的。以文献中的实验数据为出发点,分析了脊形波导的偏振问题,并通过对脊型波导器件层厚度、脊高、脊宽进行优化设计,得到了不同偏振模式的有效折射率差仅为10^-5量级的单模脊型波导结构,这样的偏振效应在器件设计中可以忽略。     

Parameter optimization and structural design of polymer arrayed waveguide grating multiplexer

First some important parameters are optimized for the structural design of a polymer arrayed waveguide grating (AWG) multiplexer around the central wavelength of 1.55 μm with the wavelength spacing of 1.6 nm. These parameters include the thickness and width of the guide core, mode effective refractive indices and group refractive index, diffraction order, pitch of adjacent waveguides, length difference of adjacent arrayed waveguides, focal length of slab waveguides, free spectral range (FSR), the number of input/output (I/O) channels, and that of arrayed waveguides. Then the bent angles, radii and lengths of all the input/output channels and arrayed waveguides are determined. Finally, a schematic waveguide layout of this device is presented, which contains 2 slabs, 11 input channels, 11 output channels, and 91 arrayed waveguides.     

Semi-Analytical Simulation of Titanium-Indiffused Lithium Niobate-Integrated Optic Directional Couplers Consisting of Curved Waveguides

Integrated optic directional couplers consisting of curved waveguides are simulated analytically by solving the Riccati equation. The coupling coefficient between the curved waveguides with a parabolically varying gap and the condition of total power transfer between the waveguides are derived. In order to compute the overall coupling coefficient and hence the power distribution along the waveguides for Ti:LiNbO₃ curved waveguide directional couplers, the coupling coefficient for straight waveguide couplers is computed for different gaps using the effective-index-based matrix method (EIMM). Finally, the power distribution in the curved waveguides along the length is computed. The method is mostly analytical except the effective-index method and is computationally simple.     

PDL free plasma enhanced chemical vapor deposition SiC optical waveguides and devices

Planar silicon carbide (SiC) waveguides are proposed for fabrication on a silicon substrate with an oxide isolation layer. Using post deposition annealing it is possible to achieve low polarisation-dependent loss (PDL) within optical SiC waveguides fabricated using a low temperature deposition technique. The proposed waveguides are optically characterised and successfully used in power splitters and vibration sensors. Results before and after annealing cycles for those devices are discussed. The interesting optical characteristics of SiC waveguides as well as the first passive components presented open the way for photonic sensing in harsh environment where SiC is a very promising material.     

Waveguide discrete modes in slab and cylindrical FIR laser

The characteristic equation is solved for oversized slab and cylindrical hollow waveguides. The outter medium is a dielectric or a metal for cylindrical waveguides, and a dielectric for slab waveguides. The results are applied to consider the resonance conditions for a FIR laser cavity.     

Surface plasmon polariton waveguides with subwavelength confinement

Surface plasmon polaritons(SPPs) are evanescent waves propagating along metal-dielectric interfaces, which provide an effective way to realize optical wave guiding with subwavelength confinement. Metallic nanostructures supporting SPPs,that is, plasmonic waveguides, are considered as required components to construct nanophotonic devices and circuits with a high degree of miniaturization and integration. In this paper, various types of plasmonic waveguides operating in the visible, infrared, and terahertz regions are reviewed, and the status of the research on their fundamentals, fabrications,and applications is provided as well. First, we discuss the mechanisms of SPPs beyond the diffraction limit, and their launching methods. Then, the characteristics of SPPs on various plasmonic waveguides are reviewed, including top-down and bottom-up fabricated types. Considering applications, certain prototypes of plasmonic devices and circuits constructed by plasmonic waveguides for bio/chemo sensing, router, and light modulation are demonstrated. Finally, a summary and future outlook of plasmonic waveguides are given.     

New method for calculating the spectra and radiation losses of leaky waves in multilayer optical waveguides

The efficiency of a new method for calculating the spectrum and attenuation coefficient of leaky electromagnetic modes is demonstrated with multilayer planar optical waveguides the guiding properties of which are determined by antiresonant reflection from the multilayer cladding (antiresonant reflecting optical waveguides) rather than by total internal reflection from the core-cladding interface as in standard optical waveguides. The new method applies to calculation of both electromagnetic modes in dielectric waveguides and electron quantum states in multibarrier semiconductor heterostructures. The characteristics of multilayer waveguides calculated by the new method are compared with published data obtained from a complex dispersion relation by the transfer matrix method. As an example, the wavelength dependence of the radiation losses for the first TE mode of a planar optical waveguide containing 52 pairs of layers is calculated.     

Dispersion parameters and nonlinear optical properties of silicon nitride rib waveguides

Silicon nitride rib waveguides are numerically studied by use of a full-vectorial mode solver program based on finite difference method. Dispersion parameters, up to the third-order, are computed for waveguides of heights 0.8 μm, 0.9 μm, and 1 μm. Like silicon-on-insulator waveguides, silicon nitride rib waveguides allow us to tailor dispersion parameters at telecom wavelengths. Deeply-etched silicon nitride rib waveguides of height up to 1.5 μm are investigated for correct geometries to achieve polarization independence. The computations lead to a minimum etch depth which can be written as linear function of the waveguide height. Etch-depth and waveguide height dependencies of the nonlinear refractive index coefficient of the silicon nitride are studied. It is shown that third-order optical nonlinearities in silicon nitride rib waveguides can be enhanced by suitable choices of waveguide parameters.     

Temperature distribution along oversized hollow-core waveguides for CO2 laser radiation

Temperature distributions along various hollow waveguides are fully analysed experimentally when the waveguides are excited by CO₂ laser light. It is shown that the temperature decreases in an oscillatory manner along the waveguides due to the interference effect of guided modes. The distributors are well explained by a theory developed previously.     

Grey screening-photovoltaic soliton-induced waveguides

This paper shows that waveguides induced by grey screening-photovoltaic solitons are always single mode for all intensity ratios, which are the ratio between the peak intensity of the soliton and the dark irradiance. It finds that the confined energy near the centre of the grey soliton and the propagation constant of the guided mode increase monotonically with increasing intensity ratio. On the other hand, when the soliton greyness increases, the confined energy near the centre of the grey soliton and the propagation constant of the guided mode reduce monotonically. When the bulk photovoltaic effect is neglected for short circuits, these waveguides become waveguides induced by grey screening solitons. When the external bias field is absent, these waveguides become waveguides induced by grey photovoltaic solitons.[第一段]