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1.
《中国物理 B》2020,(6)
Narrowband and high-transmission optical filters are extensively used in color display technology, optical information processing, and high-sensitive sensing. Because of large ohmic losses in metallic nanostructures, metallic filters usually exhibit low transmittances and broad bandwidths. By employing both strong field enhancements in metallic nano-slits and the Wood's anomaly in a periodic metallic grating, an extra-narrowband and high-transmission metallic filter is numerically predicted in an ultrathin single-layer metallic grating. Simulation results show that the Wood's anomaly in the ultrathin(thickness H = 60 nm) single-layer metallic grating results in large field enhancements in the substrate and low losses in the metallic grating. As a result, the transmission bandwidth(transmittance T 60%) at λ = 1200 nm is as small as ?λFWHM=1.6 nm, which is smaller than 4% of that in the previous thin dielectric and metallic filters. The corresponding quality factor is as high as Q = λ/?λFWHM= 750, which is 40 times greater than that in the previous reports. Moreover, the thickness of our metallic filter(H = 60 nm) is smaller than 40% of that in the previous reports, and its maximum transmittance can reach up to 80%. In experiments, a narrowband metallic filter with a bandwidth of about ?λFWHM = 10 nm, which is smaller than 25% of that in the previous metallic filters, is demonstrated. 相似文献
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《Infrared physics》1993,34(5):467-475
A novel design for a surface relief grating with rectangular grooves is presented. The first reflected diffraction order shows experimentally 84% diffraction efficiency for a metallic grating. The required binary surface relief can be manufactured by using one single microlithographic fabrication step similar to standard processes in microelectronics. Each period of the grating consists of a subwavelength “minilattice” with a variable duty cycle. A theoretical model of the structure is presented and compared to measurements at 10.6 μm wavelength. Applications ranging from deflectors, polarizing beam splitters, variable attenuators to general diffractive components such as kinoforms for laser beam shaping are proposed. 相似文献
3.
The light transmittance of metal film with periodic slits and grooves structure has been investigated. It was demonstrated that the grooves significantly affect the transmittance of the metal film. The structure excavating two grooves symmetric to the central slit in a cell of a period grating displays a dent in the transmission spectrum comparing with the structure with only one slit in the cell. Deepening the grooves moves the dents to the longer wavelengths in the transmission spectrum. An analytical equation is also provided to approximately locate the dents. The grooves in the grating filter supply the advantage of removing the needless transmission of certain frequency. 相似文献
4.
Optical phase front control in a metallic grating with equally spaced alternately tapered slits 下载免费PDF全文
A technique capable of focusing and bending electromagnetic (EM) waves through plasmonic gratings with equally spaced alternately tapered slits has been introduced. Phase resonances are observed in the optical response of transmission gratings, and the EM wave passes through the tuning slits in the form of surface plasmon polaritons (SPPs) and obtains the required phase retardation to focus at the focal plane. The bending effect is achieved by constructing an asymmetric phase front which results from the tapered slits and gradient refractive index (GRIN) distribution of the dielectric material. Rigorous electromagnetic analysis by using the two-dimensional (2D) finite difference time domain (FDTD) method is employed to verify our proposed designs. When the EM waves are incident at an angle on the optical axis, the beam splitting effect can also be achieved. These index-modulated slits are demonstrated to have unique advantages in beam manipulation compared with the width-modulated ones. In combination with previous studies, it is expected that our results could lead to the realization of ootimum designs for plasmonic nanolenses. 相似文献
5.
D. A. Zayarny A. A. Ionin I. V. Kiseleva S. I. Kudryashov S. V. Makarov A. A. Rudenko I. A. Timkin R. A. Khmel’nitskii Ch. T. Kh. Nguen 《JETP Letters》2014,100(5):295-298
A two-dimensional square transmission diffraction grating consisting of micron holes in a gold film with a period of about 6 μm exhibits surface enhanced infrared absorption of rhodamine 6G in the range of 1400–1600 cm?1 near the edge of the lower allowed band with a gain of about 10. 相似文献
6.
将任意形状槽的连续轮廓近似用一系列相连的矩形阶梯近似,利用各阶梯面上导纳的匹配,以及槽与互作用区边界场的连续与匹配条件,获得了具有任意槽的矩形波导栅慢波结构的色散方程和耦合阻抗的表达式,并进行理论上的验证.加工制作了矩形槽波导栅模型,冷测表明理论值与测量值相吻合.分别求解几种特殊槽形矩形波导栅慢波结构的色散特性及耦合阻抗,其中,三角形结构的色散和耦合阻抗均最弱,而倒梯形结构色散最强,耦合阻抗最大.
关键词:
矩形波导栅
任意槽
色散特性
慢波结构 相似文献
7.
We propose a physical understanding of scattering by subwavelength grooves surrounding a single perfect conductor slit based
on the superposition of a cylindrical traveling surface wave and a standing surface wave. The collective reflection coefficient
was introduced to handle the multi-interaction of the surface wave between subwavelength grooves, and a slit–grooves focusing
structure was designed to demonstrate its validity. In comparison to numerical simulations by the finite difference time domain
method, the proposed method proves effective in describing the multi-interaction behavior of a surface wave and in further
refining the phase perturbation at the grooves’ exits. 相似文献
8.
The electromagnetic coupling between a two-dimensional grating of resonant gold nanoparticles and a gold metallic film is investigated. We report on the observation of multipeaks in the extinction spectra attributed to resonant modes of the hybrid system, resulting from the coupling between the localized plasmon of the nanoparticles with the underlying surface plasmon mode. Simulations based on the Fourier modal method give good agreement with the experimental measurements and allow for the identification of the respective contributions. 相似文献
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等离子体激元(surface plasmon polaritons, SPP)因其独特的光学和物理特性, 使其具有诸如透射增强和局域共振等一系列新颖现象, 已成为当前国内外学者研究的热点. 本文对基于类表面等离子体激元(Spoof Surface Plasmons, SSP)的矩形金属光栅色散特性和模式分布进行了研究. 利用本征函数法并结合场匹配条件, 获得了矩形栅表面SSP的场表达式、色散关系和模式分布, 并通过电磁仿真进行了验证. 在此基础上分析了矩形栅各参数对SSP色散及模式分布的影响, 研究结果表明: 由本征函数法获得的SSP色散特性与仿真结果基本符合; 增大金属栅高度或减小排列周期能减小SSP的相速度; 而增大金属栅周期占空比能在一定程度上拓展SSP与电子束互作用的带宽; 改变金属盖板高度对慢波SSP色散模式基本没有影响; 减小金属栅侧面宽度能增大模式之间的间隔, 从而能有效避免模式竞争的发生. 本文对基于SSP的矩形金属光栅色散特性的研究将为进一步研究SSP与电子束的相互作用, 形成高效、宽带的新型太赫兹源奠定良好的理论基础. 相似文献
12.
提出一种利用多模态耦合的开孔型宽带换能器。在传统纵振换能器前盖板一定距离处开一矩形通孔,以激发出能与纵振耦合从而拓宽频带的振动模态。以带宽为目标,利用有限元方法对通孔的长度、宽度和孔前端离前盖板端面的距离进行了优化设计,得到了最佳的开孔位置和尺寸。研制了换能器样机。测试结果表明,在12~32 kHz频带范围内,换能器有3个工作模态,后两阶模态对工作带宽的展宽有贡献。未开孔的同尺寸纵振换能器-3 dB带宽仅3 kHz,开孔换能器带宽则达10.50 kHz,有效地拓展了工作带宽。理论计算和测试结果吻合较好。 相似文献
13.
In this paper, we propose an optimizing method for the beaming effect from a slit aperture with finite metallic grooves. Aiming at the beaming effect of the structure at 0°, we analyze the effect of the parameters including groove depth, groove width and groove number of the structure on the diffraction efficiency as well as angular spectra in the far field by approximation of the boundary condition of the quasi-perfect conductor assumption and the fundamental mode. Our optimization results demonstrate that the diffraction at other angles is efficiently suppressed. Finally, we give several optimized parameters of three common wavelengths of 10.6 μm, 808 nm and 632.8 nm, on the basis of using the optimizing method. Although we analyze the beaming effect at 0° only, the method is also applicable to the analysis for other angles. 相似文献
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Changde Xie Jiangrui Gao Yimin Lian Xiaoping Yang Kunchi Peng 《Applied physics. B, Lasers and optics》1990,51(3):215-218
The increasing absorption optical bistability in a bulk ZnSe sample with quite high absorption has been observed. Our experiments show that the bistability operates only in the front surface layer of sample and that the back layer of sample can be regarded as a linear absorber and heat sink. 相似文献
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C. Weber U. Becker R. Renner C. Klingshirn 《Applied physics. B, Lasers and optics》1988,45(3):113-120
There are a great variety of optical nonlinearities that can lead to the phenomenon of laser-induced gratings (LIG) in semiconductors. In the present contribution the dynamic behaviour of an induced absorber with intrinsic bistability is investigated under excitation in a LIG self-diffraction arrangement. Using CdS as a model substance, the comparison of our theoretical model with our experimental findings gives an insight into the nonlinear dynamics of the degenerate carrier system and also an estimation of the transport properties of the electron-hole plasma. 相似文献
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The anchoring properties of substrate with a grating surface are
investigated analytically. The alignment of nematic liquid
crystal (NLC) in a grating surface originates from two
mechanisms, thus the anchoring energy consists of two parts. One
originates from the interaction potential between NLC molecules
and the molecules on the substrate surface, and the other stems
from the increased elastic strain energy. Based on the two
mechanisms, the expression of anchoring energy per unit area of
a projected plane of this grating surface is deduced and called
the equivalent anchoring energy formula. Both the strength and
the easy direction of equivalent anchoring energy are a function
of the geometrical parameters (amplitude and pitch) of a grating
surface. By using this formula, the grating surface can be
replaced by its projected plane and its anchoring properties can
be described by the equivalent anchoring energy formula. 相似文献
20.
The excitation of a surface plasmon polariton (SPP) wave on a metal–air interface by a 2D diffraction grating is numerically investigated. The grating consists of homogeneous alloys of two metals of a formula AxB1−x, or three metals of a formula AxByCz, where A, B and C could be silver (Ag), copper (Cu), gold (Au) or aluminum (Al).It is observed that all the alloys of two metals present a very small change of surface plasmon resonance (SPR) irrespective of composition x. Moreover, the addition of 25% of Al to two metals alloy is insufficient to change the SPR curves. The influence of the different grating parameters is discussed in details using rigorous coupled-wave analysis (RCWA) method. Furthermore, the SPR is highly dependent on grating periods (dx and dy) and the height of the grating h. The results reveal that dx= dy= 700 nm, h=40 nm and duty cycle w=0.5 are the optimal parameters for exciting SPP. 相似文献