Plasmonic Metasurfaces Enabled Ultra‐Compact Broadband Waveguide TM‐Pass Polarizer

Silicon waveguide polarizers offer a simple yet robust approach to address the polarization‐dependent issue of silicon‐based optical components, and hence have found numerous applications in silicon photonics. However, the available silicon waveguide polarizers suffer from the issue of large device footprint, high insertion loss (IL), and/or fabrication complexities. Here, a silicon waveguide transverse magnetic (TM)‐pass polarizer is constructed by coating a silicon waveguide with an ultra‐thin plasmonic metasurface structure that is capable of guiding slow surface wave (SW) mode. The transverse electric (TE) waveguide mode can be converted into SW mode with the involvement of metasurfaces, and hence is intrinsically absorbed and forbidden to pass, while the TM waveguide mode can be well guided due to little influence. A typical metasurface polarizer with an ultra‐short length of 2.4 µm enables the IL of 28.16 dB for the TE mode, and that of 0.53 dB for the TM mode at 1550 nm. Multiple‐band TM‐pass polarizers can be obtained by cascading two or more different metasurface‐coated silicon waveguides along the propagation direction, and a dual‐band TM‐pass polarizer is demonstrated with the IL being of 19.21 and 29.09 dB for the TE mode at 1310 and 1550 nm, respectively.     

1.5μm Ti:LiNbO_3光波导TE_0模偏振器

在1.523μm波长He-Ne激光,对于Z切Ti扩散LiNbO_3光波导及其带有金属包覆/介质缓冲层的偏振器结构,理论上计算了单模波导的工艺参数和基模的吸收损耗系数.文中用TM_0模的共振吸收效应,在1.5μm波长首次研制成Ti:LiNbO_3光波导TE_0模偏振器.当器件长度为2mm和9mm时,其消光比分别为20dB和25dB.     

High-power TE11 and TM11 circular polarizers in oversized waveguides at 70 GHz

Elliptical deformation of oversized, smooth-wall circular waveguides can produce choosable elliptical or circular polarization from a linearly polarized TE11 or TM11 mode used as intermediate linearly polarized modes in TEO1 to HE11 mode conversion sequences in electron cyclotron resonance heating (ECRH) of magnetically confined thermonuclear fusion plasmas with high-power gyrotrons. Mode coupling in elliptically distorted overmoded circular waveguides has been studied theoretically and experimentally in order to optimize TE11 (and TM11) polarizers (I.D.=27.79 mm) for the 1 MW/70 GHz long-pulse (3s) ECRH system on the Garching Stellarator W VII-AS. Coupling coefficients for ellipticity coupling of non-degenerate modes are given (coupled-mode differential equations formalism). The polarization converters essentially consist of smooth-wall circular waveguides which are gradually squeezed. A sine-squared function of the length coordinate is used to get an almost elliptical crosssection in the middle and circular cross sections at both ends. Arbitrary elliptical polarization states can be generated introducing an extremely low level (<<1%) of undesired spurious modes. Well defined differential phase characteristics have been achieved.     

Mid-infrared wire-grid polarizer with silicides

An infrared (IR) polarizer with tungsten silicide (WSi) wire grid was fabricated by two-beam interference exposure and reactive ion etching. To enhance TM transmittance, silicon monoxide was deposited between the WSi wire grid (400 nm period) and a Si substrate. The transmittance was over 80% in the 4-5 microm wavelength range. The ratio of TM and TE transmittances was over 100 (20 dB) in the 2.5-6 microm wavelength range. The fabricated polarizer has higher durability and better compatibility with microfabrication processes compared with conventional IR polarizers.     

高功率微波弯曲圆波导设计

 报道了可分别传输TM₀₁模和TE₀₁模的两种弯曲圆波导的设计方法和计算结果。研究表明：所设计的TM01模弯曲波导和TE₀₁模弯曲波导在中心频率上传输效率均超过99.5%,传输效率大于95%的带宽分别达到20.0%和14.4%;该两个弯曲波导也分别适用于传输TE₁₁模和TM₁₁模;水平极化TE₁₁模与TM₀₁模、垂直极化TM₁₁模与TE₀₁模在弯曲圆波导中传输时具有相似的传输效率和频带特性;而垂直极化TE₁₁模、水平极化TM₁₁模由于不易和其它模式耦合,在弯曲波导中传输时具有较高的传输效率。     

高功率微波TM0n混合模式转换方法

针对现有基于特定模式成分所设计的高功率mTM0n-TEM/TM01混合模式转换器的工作原理,提出了一种大过模比结构下高功率TM0n混合模式的转换方法,可以实现将状态相对稳定且成分已知的GW量级任意模式成分比例、任意相位差的高功率TM0n混合模式微波高效转换为单一的TEM模或TM01模。利用该设计原则对之前所设计的高功率TM0n混合模式转换器进行优化改进,在保留了原有器件功率容量和频带特性的同时,大幅简化器件设计结构。     

Wide-range optical sensors based on a single ring resonator with polarization multiplexing

Wide-range optical sensors based on a single ring resonator are investigated theoretically and experimentally.The sensor worked at the TE and TM modes simultaneously. Because the sensitivities of the TE mode and TM mode are different, the TE mode is used for the large measurement range, and the TM mode is used for the high sensitivity measurement. The experimental results showed that the measurement range for the TE mode was almost three times larger than that of the TM mode. A sensitivity of 233 nm/RIU was achieved for the wavelength interrogation of the TM mode.     

基于Ti扩散铌酸锂偏振分束器的研制

对定向耦合型偏振分束器的原理进行了分析。设计了一种零间距定向耦合器,在空间上实现TE/TM模式分束;用BPM软件对所设计的器件进行仿真模拟,对于TE/TM模的消光比分别可以达到21.2dB和19.5dB;该器件在X切Y传的LiNbO3晶片上采用Ti扩散技术制作完成。实验样品消光比测试结果TE/TM模分别为11.5dB和19.1dB,对于消光比不够理想的原因进行了初步的分析。     

太赫兹量子级联激光器光束特性分析

用有限元法计算太赫兹量子级联激光器激光模式的阈值增益.结果表明:接触层厚度和掺杂浓度对阈值增益的影响远远大于波导宽度和激射波长;接触层厚度较小(大)和掺杂浓度较低(高)时,TM₁(TM₀)模的阈值增益较小.在此基础上,用矢量衍射理论分析岀射光束的远场特性,得到光束的远场光斑基本是椭圆;x方向的远场散射角随波导宽度或激射波长的增加分别线性减小或增加,尽管对应的接触层厚度和掺杂浓度不同,但TM₀和TM₁模x方向的远场散射角相同;另外,还得到y方向远场散射角不受波导宽度或少受激射波长的影响.在阈值增益和光束质量方面,TM₁模都优于TM₀模.     

TM020模式谐振腔束团长度监测器的设计与仿真（英）

提出了一种基于高次模式的谐振腔束团长度测量技术,新方法的谐振腔工作于高次本征模式TM0n0。这样的谐振腔拥有更大的腔体半径,从而移除了谐振腔半径必须大于束流管道半径这一原则带来的工作频率限制。为国家同步辐射实验室未来的正电子源设计了一台双腔束团长度监测器,讨论了谐振腔工作频率的选择并推导了束团长度的计算公式,监测器的谐振腔工作于TM020模式,其半径远大于使用TM010模式的传统方法,在CST软件中模拟的结果显示其束团长度测量精度好于7%。     

Theoretical study of polymeric metal clad optical waveguide polarizer

Planar optical waveguides consisting of thin dielectric films and buffer layers with metal cladding have been investigated theoretically. A computer program was written to calculate the exact zeroes of complex eigenvalue equation for TE and TM modes in multilayer metal clad waveguide polarizer. Numerical results and illustrations are given for Polycarbonate waveguide with other polymers as buffer and Al, Ag and Au as cladding metals at . It is also shown that, using thin (finite) films of metal produce more efficient polarizers as compared to semi-infinite metal films. Effect of low index buffer layer on attenuation of TM/TE modes is also investigated.     

TE, TM modes photorefractive surface waves and their coupling

The nonlinear equations of photorefractive surface waves (PR SWs) with diffusion mechanism are established and calculated numerically for both TE mode and TM mode and their coupling for the first time. The characteristics of TE mode and TM mode are analyzed, such as propagation constants, spatial distribution, penetration depths etc. For relative larger propagation constant, most of the surface wave energy is concentrated on the A_x component of TM mode, and the penetration depth of A_y of TE mode is always larger than that of A_x of TM mode because electro-optical coefficient r₁₃ is always smaller than r₃₃ in general PRC. As a result, the energy of the PR SW is better confined near the surface for TM mode than that for TE mode. When both TE and TM modes PR SWs are present, they will be coupled drastically and the A_x component of TM mode and A_y component of TE mode resonate in the volume of PR medium. As a result, the PR SWs cannot remain decay, and the light energy can not be confined near the surface steadily and the modes are destroyed. The results provide the theoretical instructions and are very significant to generate steady and high density PR SW in practice.     

质子交换的新型集成光学TM通偏振器的研究

提出了用扩钛和质子交换相结合的方法在x-切,y-传的LiNbO3 衬底上制成TM 通集成光波导偏振器的新方案, 即在扩钛波导两侧的适当位置引入锯齿形的质子交换区。用二维BPM法分析了这类新型偏振器的消光特性, 给出了质子交换区几何形状以及质子交换区与扩钛波导之间的间隙对TE波消光比的影响, 给出了数值分析结果, 并得到了优于23 dB的实验结果     

紧凑型菱形缝隙V波段过模圆波导选模耦合器

设计了一种用于测量V波段过模高功率毫米波源在线功率的选模耦合器。利用小孔耦合理论和微元法对菱形耦合缝隙进行了理论分析，采用两组相同的菱形耦合缝隙实现选模功能，缩短了耦合器长度，增加了工作带宽。采用数值模拟的方法对耦合器结构进行优化设计，模拟结果表明:在60 GHz频点处，TM01模耦合度约为50 dB，TM02模耦合度仅为75 dB，对TM02模的抑制度为25 dB；在500 MHz带宽内对TM02模的抑制度大于15 dB，1 GHz带宽内的抑制度大于10 dB，可满足工作于TM01模的V波段高功率毫米波测试需求。同时针对工作于高次模TM0n（n=2,3,4,）的器件设计了可抑制TM01模的耦合器，为高次模工作的高功率毫米波器件的在线功率测量和模式诊断提供了技术方案。     

Fabrication of a mid-IR wire-grid polarizer by direct imprinting on chalcogenide glass

A mid-IR wire-grid polarizer with a 500 nm pitch was fabricated on a low toxic chalcogenide glass (Sb-Ge-Sn-S system) by the thermal imprinting of periodic grating followed by the thermal evaporation of Al metal. After imprinting, deposition of Al on the grating at an oblique angle produced a wire-grid polarizer. The fabricated polarizer showed polarization with TM transmittance greater than 60% at 5-9 μm wavelengths and an extinction ratio greater than 20 dB at 3.5-11 μm wavelengths. This polarizer with a high extinction ratio can be fabricated more simply and less expensively than conventional IR polarizers.     

THE CASIMIR FORCE BETWEEN POLARIZERS

The Casimir force between two parallel lincar polarizers oriented at an arbitrary angle is calculated. We compare two approaches, one by solving the field mode function in three-dimensional space with highly anisotropic dielectric slabs, the other by calculating the interaction between dipolcs induced by vacuum fluctuations in these slabs.     

Finite Element Analysis of the Field Patterns in Elliptical Waveguide

In this paper, finite element method is first used to discuss the field patterns in a hollow perfectly conducting pipe with elliptical cross section. The electrical field lines of the dominant TE mode as well as the magnetic field lines of the lowest TM mode are presented. The results are the same with literatures, and also give a correction to the field pattern of the lowest TM mode in elliptical waveguide.     

InGaAs/InAlAs多量子阱脊形波导及定向耦合器光波特性准矢量分析

提出了一种基于级数展开的三维准矢量束传播法(SE-QV-BPM)用以分析由InGaAs/InAlAs多量子阱构成的脊形光波导及定向耦合器.结果表明，刻蚀深度相同时，TM模比TE模在水平方向限制强，且TM模的模场在波导角上出现畸变；波导间距相同时，定向耦合器TM波的耦合长度大于TE波的耦合长度，对偏振态敏感.分析获得了浅/深刻脊形光波导承载的准矢量TE/TM基模、定向耦合器承载的TE/TM偶/奇模的模场分布及其有效折射率，模拟了光场在定向耦合器中的传输演变情况.另外，SE-QV-BPM导出矩阵小，计算效率高 关键词： 级数展开 准矢量束传播法 多量子阱 InGaAs/InAlAs     

用转移矩阵法研究LNN型非线性平面光波导

用转移矩阵法数值分析了芯区和衬底为非线性介质、覆盖层为线性介质结构平面光波导的传播特性,包括TM的模场分布和功率与有效折射率之间关系的分析.解析地表达了模式本征方程和功率分布,对非线性介质中电场强度与介质非线性系数的关系进行了研究.计算结果表明,TM的模场分布和功率与有效折射率及介质的非线性系数有关.     

The Casimir interaction of a massive vector field between concentric spherical bodies

The Casimir interaction energy due to the vacuum fluctuations of a massive vector field between two perfectly conducting concentric spherical bodies is computed. The TE contribution to the Casimir interaction energy is a direct generalization of the massless case but the TM contribution is much more complicated. Each TM mode is a linear combination of a transverse mode which is the generalization of a TM mode in the massless case and a longitudinal mode that does not appear in the massless case. In contrast to the case of two parallel perfectly conducting plates, there are no TM discrete modes that vanish identically in the perfectly conducting spherical bodies. Numerical simulations show that the Casimir interaction force between the two bodies is always attractive.