双层金属纳米光栅的TE偏振光异常透射特性

根据在亚波长金属光栅表面添加电介质会引起TE偏振光的透射异常性, 应用严格耦合波理论和时域有限差分方法, 研究了双层金属纳米光栅在TE偏振光入射时产生的异常透射现象. 利用等效折射率方法建立了双层金属光栅的等效模型, 得到了TE偏振光透射率与聚合物的折射率、厚度以及金属层厚度的变化关系. 确认了结构中聚合物是透射异常出现的必要条件, TE偏振光以波导电磁模式在其中传播, 并认为类Fabry-Perot腔谐振是透射峰值产生的主要原因.     

Broadband Terahertz Polarization Converter and Asymmetric Transmission Based on Coupled Dielectric‐Metal Grating

Coupled dielectric‐metal gratings are investigated for broadband terahertz (THz) wave polarization conversion and asymmetric transmission by the experiments and numerical simulations, which are composed of the subwavelength Si grating and metallic wire grating layers. The dielectric grating layer with a large artificial birefringence and low dispersion is employed as a phase engineered waveplate, and the metal wire grating arranged with a 45° angle to the dielectric grating is utilized as a high‐efficiency polarizer. Due to the subwavelength integration, this coupled grating presents a local resonance coupling mechanism between dielectric and metal gratings, which greatly enhances the polarization rotation and expands the bandwidth, not a simple combination with dielectric and metallic gratings. The results demonstrate that a broadband asymmetric transmission with an extinction ratio of 30dB from 0.2 to 1.2 THz is achieved and the highest transmission of 90% can be obtained. It provides a simple way towards practical applications for THz artificial dispersion materials, polarization control and asymmetric transmission.     

Magneto-optical effects for detection of in-plane magnetization in plasmonic crystals

Methods for magneto-optical detection of the in-plane magnetization in a magnetic film due to the deposition of a one-dimensional metallic diffraction grating on the film have been considered. This structure is a magnetoplasmonic crystal, in which the excitation of the waveguide and plasmon modes leads to the appearance of five resonant magneto-optical effects that consist in a change of the intensity, the polarization, and the phase of the transmitted and reflected waves. The conditions responsible for the origin of these effects and their magnitude are determined by the configuration of the incident light, the parameters of the metallic grating, and the chemical composition of the magnetic layer. It has been found that the magnetophotonic intensity effects are the most optimal for the detection of the in-plane magnetization. The influence of the parameters of the metallic grating on the magneto-optical effects has been analyzed and the most optimal conditions for the observation of these effects have been determined. It has also been found that an increase in the concentration of bismuth in a magnetic dielectric material can lead to a weakening of the optical and magneto-optical responses.     

Numerical Investigation of Surface Plasmons Associated Subwavelength Optical Single-Pass Effect

Surface plasmons （SPs） associated optical single-pass effect has been investigated in novel subwavelength metallic structures, including single slit and grating structures. With influence of SPs, these metallic structures can enhance transmission in incident direction and suppress it in the opposite direction, exhibiting a single-pass effect. The finite difference time domain method is employed to study the influences of structure parameters on far-field transmission, near-field electric field distribution and extinction ratio of the single-pass transmission effect. A maximal extinction ratio of 47.83dB is achieved in the grating structure.     

Surface plasmon resonance transmission filters at 1053nm based on metallic grating with narrow slit

Metallic gratings with narrow slits can lead to special optical properties such as strongly enhancing the transmission and considerably strengthening the polarized effect. A narrow-band filter suitable for application in optical communication is designed by sandwiching a metallic grating between two identical dielectric films. The maximum transmission can reach 96% after optimizing the parameters of films and grating at a central wavelength of 1053 nm. It is the first time, to our knowledge, that such high transmission has been reported since the discovery of the extraordinarily high transmission through periodic holes or slits; moreover, the extremely polarized effect is also found in P mode of this symmetric grating.     

Transmission and directionality control of light emission from a nanoslit in metallic film flanked by periodic gratings

We investigate the transmission and directional properties of light emission from a nanoslit film flanked by periodic gratings, formed on a silver film, embedded in a high index dielectric medium. Using FDTD calculations it is demonstrated that the transmission has strong dependence on dimension of the dielectric film. The directional property of the emitted beam is controlled by tapering height of output grating elements and this effect is explained by standard theory of antenna array. We propose and examine the potential of such slit grating structure as a Plasmonic antenna in axial injection of light from single mode fiber to photonic crystal waveguide.     

Extraordinary optical transmission for TE wave through metallic sub-wavelength grating with slits filled with dielectric

A metallic sub-wavelength grating with slits filled with dielectric was proposed to achieve broadband and enhanced Extraordinary Optical Transmission (EOT) for Transverse Electric (TE) wave. The physical mechanism for the improvements of the transmission spectrum was also revealed. It was found that the Fabry–Perot cavity resonance in the grating slits was the cause of the enhancement of the EOT and the waveguide modes theory was the fundamental mechanism for the broadened bandwidth of the transmission.     

深紫外双层金属光栅偏振器的设计与分析

193 nm波长浸没式步进扫描投影光刻机是实现45 nm及以下技术节点集成电路制造的核心装备.增大数值孔径是提高光刻分辨率的有效途径,而大数值孔径曝光系统的偏振性能严重影响光刻成像质量.光刻机曝光系统偏振参数的高精度检测是对其进行有效调控的前提.基于光栅的偏振检测技术能实现浸没式光刻机偏振检测装置的小型化,满足其快速、...     

Optical switching in metal-slit arrays on nonlinear dielectric substrates

We propose a scheme for an optical limiter and switch of the transmitted light intensity in an array of subwavelength metallic slits placed on a nonlinear Kerr-type dielectric substrate of finite thickness, where the geometrical parameters are designed for operation at telecom wavelengths. Our approach is based on the abrupt changes of the output light intensity observed in these systems near transmission minima.     

Combined Diffraction Grating in the Scheme of Grazing Incidence: Calculation and Parameter Optimization

The method of parameter optimization of combined structures, which consist of a dielectric grating and a metallic or multilayer dielectric mirror, was proposed. It is based on the use of the waveguide properties of the combined diffraction grating. Its main advantage lies in the possibility of determining the optimum parameters of the combined grating without solving the diffraction problem.     

级联亚波长平面介质栅偏振分束器研究

提出了一种纳米厚度金属层连接的级联亚波长平面介质光栅三明治结构,利用该结构中纳米金属连接层上下界面处的表面等离子共振的互作用形成多波长共振的特点设计了适用于光通信波段（1 300～1 600nm）高性能的宽带偏振器和宽带偏振分束器。利用严格耦合波理论分析发现偏振分束器带宽主要由金属连接层厚度控制,光栅厚度基本不影响偏振分束器带宽,只影响共振深度和共振波长。该结论为后续的制备提供了理论指导和借鉴作用。     

Enhanced light transmission through cascaded metal films perforated with periodic hole arrays

We report experimental results on enhanced light transmission through two periodically perforated metal films separated by a layer of dielectric. A perforated metal film (single metallic structure) exhibits extraordinary optical transmission, and when two such perforated metal films are spaced by a dielectric layer (cascaded metallic structure), the transmission is further increased. The maximum transmission of the cascaded metallic structure, which depends on the distance between the two metal films, can be more than 400% greater than that of a corresponding single metallic structure. It is proposed that the coupling of surface plasmon polaritons between the two metal films is involved in the process.     

Enhanced optical transmission through a subwavelength 1D aperture

We present finite difference time domain simulations of the enhancement of the optical transmission through a single subwavelength slit in a thick metal film caused by resonances of the electromagnetic fields in and near the slit. These can be enhanced by including a periodic modulation on the in-coupling surface, and the dependence of the transmission on the grating structural parameters is analysed in detail.     

High dielectric anisotropy compound doped transmission gratings of HPDLC

Effects of high dielectric anisotropy compound (MLC) and oligomer molecular weight on the grating formation and electro-optical properties of transmission holographic polymer dispersed liquid crystal (HPDLC) have been studied. Addition of MLC reduced the response time and switching voltage with the increased formulation viscosity which introduced a sequence of phenomenon, i.e. slow diffusion, polymerization, phase separation, grating formation, and droplet coalescence giving small droplet size and enhanced diffraction efficiency of the film. Apparently, increase in oligomer molecular weight gave effects similar to those of increasing MLC content since both variables control droplet coalescence through different mechanisms.     

Light transmission through metal films perforated with arrays of asymmetric cross-shaped hole

The transmission characteristics of metallic film perforated with an array of asymmetric cross-shaped hole are studied by using the three-dimensional finite difference time-domain method. We find that the wavelengths and intensities of transmission peaks depend strongly on the asymmetric parameters of the cross-shaped hole. The transmission peaks in the structure of asymmetric cross-shaped hole array originate from the splitting of the transmission peak in the corresponding one of symmetric cross-shaped hole array. Moreover, it is also found that the transmission spectra can be adjusted by changing other geometrical parameters of asymmetric cross-shaped hole due to the their effect on the distribution of the oscillating charges on metal surfaces.     

Multiple paths to enhance optical transmission through a single subwavelength slit

In this Letter, we explore transmission properties of a single subwavelength slit flanked by a finite array of grooves made on a thick metallic film. We identify three main mechanisms that can enhance optical transmission: groove cavity mode excitation (controlled by the depth of the grooves), in-phase groove reemission (controlled by the period of the groove array), and slit waveguide mode (controlled by the thickness of the metal film). By tuning these geometrical parameters, enhancements of transmission of light by up to 2 orders of magnitude can be achieved when all three mechanisms coincide. Experimental verification of these findings is also shown for structured silver films fabricated by focused-ion-beam milling.     

High-efficiency, high-dispersion diffraction gratings based on total internal reflection

We report a new class of high-dispersion immersed diffraction gratings for which the reflective nature of the diffraction is provided by the phenomenon of total internal reflection (TIR) regardless of grating tooth shape. Thus, the component can be fabricated from a single dielectric material and requires no metallic or dielectric film layers for high reflection diffraction efficiency. With the absence of metallic absorption, diffraction efficiencies of these TIR gratings can reach more than 99% for 15-20-nm spectral bandwidths, making them suitable for many laser-based technologies.     

多层介质膜脉宽压缩光栅的严格矢量分析

用于展宽和压缩激光脉冲的多层膜脉宽压缩光栅是由多层介质高反膜和位于其顶层的浮雕光栅构成。以设计的高反射多层膜为基础,利用傅里叶模式理论分析了其衍射场分布,给出了TE波自准直角入射的使用条件下,多层介质膜脉宽压缩光栅衍射效率的表达式。以-1级衍射效率为评价函数,分别讨论了HfO2和SiO2为顶层材料时,多层膜脉宽压缩光栅-1级衍射效率高于0.95的光栅结构参量范围。结果表明,在该条件下,选择HfO2为顶层材料时,光栅结构参量有较大的取值范围。给出了优化的光栅结构参量,并分析了光栅制作误差及其使用条件的宽容度,对光栅制作工艺和使用具有一定的指导意义。     

Design of Highly Sensitive Surface Plasmon Resonance Sensors Using Planar Metallic Films Closely Coupled to Nanogratings

We investigate the sensitivity enhancement of surface plasmon resonance （SPR） sensors using planar metallic films closely coupled to nanogratings. The strong coupling between localized surface plasmon resonances （LSPRs） presenting in metallic nanostructures and surface plasmon polaritons （SPPs） propagating at the metallic film surface leads to changes of resonance reflection properties, resulting in enhanced sensitivity of SPR sensors. The effects of thickness of the metallic films, grating period and metal materials on the refractive index sensitivity of the device are investigated. The refractive index sensitivity of nanograting-based SPR sensors is predicted to be about 543 nm/RIU （refractive index unit） using optimized structure parameters. Our study on SPR sensors using planar metallic films closely coupled to nanogratings demonstrates the potential for significant improvement in refractive index sensitivity.     

Near field of terahertz radiation transmitted through a lateral non-centrosymmetric grating

The transmission of a terahertz (THz) wave through a grating of metallic strips deposited on a flat surface of a dielectric medium has been considered. It has been assumed that the unit cell of the lateral grating does not have a spatial inversion center and the grating period is small compared to the radiation wavelength. The found amplitudes and phases of the spatial harmonics of the transmitted wave in the near field have been used to calculate the components of the tensor of asymmetry parameters responsible for the generation of photocurrents in a doped quantum well embedded in the non-centrosymmetric system under consideration. It has been found that, at a strip height greater than the skin depth, the parameters of the transmitted spatial harmonics are nearly independent of the height. It has been shown that the metallic grating exhibits strong birefringence, and the radiation polarized either circularly or linearly at an angle of 45° with respect to the principal axes of the lateral grating induces superposition of photocurrents owing to the circular or linear electronic ratchet effects.