紫外表面等离激元在基于氧化锌纳米线的半导体-绝缘介质-金属结构中的输运特性研究

研究了紫外表面等离激元在半导体纳米线-绝缘介质-金属构成的波导结构中的输运问题,借助有限元方法,对这种波导所支持导模的电磁能分布、有效折射率、传播长度和有效模场面积随电磁参数和几何结构参数的依赖关系进行了分析.计算结果表明:以氧化锌纳米线作为增益介质,绝缘材料选择折射率小的空气,金属选择铝能够实现对输出光场的亚波长约束,有效模场面积达到λ2/100,同时保持低的传输损耗和高场强限制能力;有望用作纳米光源,使得相关的生物探测器件和医疗诊断设备实现更高的灵敏度和更小的体积.     

A hybrid long-range surface plasmon waveguide comprising a narrow metal stripe surrounded by the low-index dielectric regions

A novel hybrid long-range surface plasmon waveguide structure comprising a narrow metal stripe, two relative low-index dielectric regions and dielectric ridges is proposed and analyzed. With the dielectric ridges and the two relative low-index dielectric regions symmetrically distributed on both sides of the narrow metal stripe, a symmetric hybrid long range mode with low electromagnetic transmission loss and subwavelength scale confinement is achieved. By optimizing the parameters, the propagation length of the proposed waveguide is increased to over two times to that of the conventional symmetric dielectric loaded surface plasmon waveguide, but the mode size only increases about 20%. For this benefit, the hybrid long-range surface plasmons waveguide is a good candidate for realizing high density photonic integration circuits.     

Long-range dielectric-loaded surface plasmon polariton waveguides operating at telecommunication wavelengths

We report on the realization of long-range dielectric-loaded surface plasmon polariton waveguides (LR-DLSPPWs) consisting of straight and bent subwavelength dielectric ridges deposited on thin and narrow metal stripes supported by a dielectric buffer layer covering a low-index substrate. Using imaging with a near-field optical microscope and end-fire coupling with a tapered fiber connected to a tunable laser at telecommunication wavelengths (1425-1545?nm), we demonstrate low-loss (propagation length ～500?μm) and well-confined (mode width ～1?μm) LR-DLSPPW mode guiding and determine the propagation and bend loss.     

Gain-assisted propagation of electromagnetic energy in subwavelength surface plasmon polariton gap waveguides

The propagation of electromagnetic energy via coupled surface plasmon polariton modes in a metal-insulator-metal heterostructure is analyzed analytically for a core material exhibiting optical gain. It is shown that a sufficiently large gain can completely compensate for the absorption losses due to energy dissipation in the metallic boundaries, enabling long-range transport with a confinement below the diffraction limit for on-chip switching and sensing applications. For a free-space wavelength of 1500 nm, lossless propagation in a gold-semiconductor-gold waveguide with a core size of 50 nm is predicted for a gain coefficient γ = 4830 cm⁻¹, comparable to that of semiconductor gain media. The gain requirements decrease with the use of low-index nanocrystal-doped glasses or polymers as core materials.     

A long-range hybrid THz plasmonic waveguide with low attenuation loss

Numerical solutions are obtained for the proposed novel hybrid terahertz plasmonic waveguide structure, namely the silicon metal silicon (SMS) waveguide. It is shown that the SMS waveguide can overcome the diffraction limit while still maintaining a sizeable propagation length. The geometric dependence of the mode characteristics of this structure is analyzed in detail, showing strong confinement and low loss with propagation lengths exceeding 14 mm at normalized mode areas of 1.72 × 10⁻². By using the FEM method (Comsol), the guiding properties of the hybrid terahertz surface plasmon polariton (HTSPP) waveguide are numerically analyzed at the THz frequency, and a combination of double-structured comparisons of the best features of the terahertz plasmonic waveguide is made. Depending on the height used and how the mode confinement is measured, various modal designs, such as double microwire structures, are developed. The structures indicate that we verified the possibility of low attenuation loss of hybrid THz plasmonics propagation. The effective mode area A_eff, energy distribution, and propagation length L_p versus height for waveguides with Si microwire and SiO₂ are shown. The numerical calculation results reveal a potential for use in applications such as optical force in trapping and transporting biomolecules, and in high-density integrated circuits.     

Efficient second-harmonic generation in nonlinear plasmonic waveguide

We theoretically studied a nonlinear optical process in a hybrid plasmonic waveguide composed of a nonlinear dielectric waveguide and a metal film with a separation of a thin air gap. Owing to the hybridization effect of guided mode and surface plasmon polariton mode, this particular waveguide is able to confine the optical-field in a deep subwavelength scale together with low propagation loss. Based on this, efficient second-harmonic generations (SHG) were revealed at the fundamental wavelength of λ=1.55?μm with good field confinement. The SHG efficiency, as well as the coupling coefficient and mode area, were analyzed and discussed in detail with respect to the structural parameters.     

Analysis of surface and guided wave plasmon polariton modes in insulator–metal–insulator planar plasmonic waveguides

Theoretical and experimental study of the surface plasmon–polariton and guided wave plasmon polariton modes is presented for the Sapphire/Ag/Polycarbonate/Air structure. Theoretical results are obtained by solving complex multilayer eigenvalue equations as well as the reflectivity equation for this structure. It is proposed that the mode attenuation can be significantly reduced by inserting a low index dielectric buffer between the metal and the guiding dielectric layer. The dispersion and attenuation curves are generated. Both the surface plasmon and guided wave plasmon polariton modes are studied experimentally. The experimental values of the effective refractive indices agree well with the theoretical values. The electric field profiles are generated and used to examine the nature of modes. After optimization of various parameters the condition for low loss single mode guiding is obtained for the proposed structure. Effect of metal thickness on surface plasmon mode is also discussed. It is inferred that in a properly optimized plasmonic waveguide, the losses can be reduced by a factor of 4.     

Plasmonic waveguiding in a hexagonally ordered metal wire array

We propose the inclusion of a structured pattern of nanoscale metal wires in a silica fiber to form a symmetric plasmonic waveguide. The surface plasmon polariton modes within the waveguide are studied by varying the wire diameter and spacing. Simulation results show that hybridization of the single-wire mode and the gap plasmon mode can yield a hybrid mode with optimum propagation lengths comparable to those reported for other structures but with better light confinement. The fiber can be easily doped with a gain material to offset the loss so that the resultant waveguide will be useful for integration with electronic circuits at nanometer dimensions.     

Simulation investigation on channel surface plasmon guiding by terahertz wave through subwavelength metal V-groove

The waveguide propagation properties of terahertz wave through subwavelength metallic triangular groove channels have been simulationally investigated. The effects of groove depth, groove angle and dielectric filling materials on propagation property have been shown and discussed. The results show that with increasing of groove depth and angle degree the propagation constant of channel surface plasmon polariton mode decreases. The propagation constant of poor conductive metal is larger than that of good conductive metal, which may result from the fact that the former has larger skin depth. In addition, the confinement of CSPP mode could be improved by increasing the refractive index of dielectric filling materials.     

Hybrid plasmonic waveguide with gain medium for lossless propagation with nanoscale confinement

In this Letter, we propose a hybrid plasmonic nanosystem consisting of a silver cladding layer with a semicylinder bump on top of InGaAsP nanowire. Because of the coupling between the dielectric waveguide mode and surface plasmon polariton mode, the hybrid plasmonic mode can exhibit low loss with strong field localization. The finite element method numerical simulations are employed to evaluate the performances of the hybrid mode. In order to achieve the lossless propagation of the hybrid mode with the mode area of 0.0058(λ2/4) at 1.55 μm, the material gain of 200 nm × 300 nm InGaAsP nanowire should reach 1223 cm?1.     

Long-Range Surface Plasmon Polaritons Guided by a Thin Metal Stripe

A long-range surface plasmon polariton （LRSPP） waveguide consisting of a 15nm thick gold stripe embedded in a homogeneous polymer BCB is reported. LRSPPs are excited by TM-mode input light successfully using an end-fire method. By scanning the output coupling fibre, the near field of the LRSPP is measured. The propagation loss of as low as 2.34 dB/mm is demonstrated.     

Research progress of femtosecond surface plasmon polariton

As the combination of surface plasmon polariton and femtosecond laser pulse,femtosecond surface plasmon polariton has both nanoscale spatial resolution and femtosecond temporal resolution,and thus provides promising methods for light field manipulation and light-matter interaction in extreme small spatiotemporal scales.Nowadays,the research on femtosecond surface plasmon polariton is mainly concentrated on two aspects:one is investigation and characterization of excitation,propagation,and dispersion properties of femtosecond surface plasmon polariton in different structures or materials;the other one is developing new applications based on its unique properties in the fields of nonlinear enhancement,pulse shaping,spatiotemporal super-resolved imaging,and others.Here,we introduce the research progress of properties and applications of femtosecond surface plasmon polariton,and prospect its future research trends.With the further development of femtosecond surface plasmon polariton research,it will have a profound impact on nano-optoelectronics,molecular dynamics,biomedicine and other fields.     

Graded-index ridge surface plasmon polaritons waveguide

We propose and analyze a long-range dielectric-loaded surface plasmon polariton （SPP） waveguide based on graded-index ridge over server millimeter distances. Then the influence of the dielectric thickness and the ridge refractive index on propagation length and mode width is discussed and simulated with the finite ele- ment raethod. The result shows that the SPP can propagate as long as 3.42 mm, as well as the mode width keeping as 1.64μm, a better one compared with the fixed refractive index. Considering its nanoscale dimension and outstanding performance, the structure is easily realized when connected with electrodes.     

Dispersion and damping of a surface plasmon polariton on a one-dimensional randomly rough metal surface

Abstract

By the use of the reduced Rayleigh equation for the amplitude of a surface plasmon polariton on a one-dimensional randomly rough metal surface that is in contact with vacuum, we calculate the dispersion and damping of the surface electromagnetic wave to the lowest nonzero order in the rms height of the surface. It is found that the frequency of the surface plasmon polariton is depressed by the surface roughness. The attenuation of the surface plasmon polariton in the long wavelength limit is due primarily to its scattering into other surface plasmon polaritons, while in the short wavelength limit it is due primarily to its roughness-induced scattering into volume electromagnetic waves in the vacuum. The energy mean free path of the surface plasmon polariton is shorter on a randomly rough metal surface than it is on a lossy planar metal surface, and the surface plasmon polariton is more tightly bound to a rough surface than to a planar one.     

Hybrid vertical directional coupling between a long range surface plasmon polariton waveguide and a dielectric waveguide

To investigate light coupling between a long range surface plasmon polariton (LRSPP) waveguide and a conventional integrated optical component, a hybrid vertical directional coupler consisting of a LRSPP waveguides and a dielectric waveguide is investigated and fabricated. In the proposed coupler the dielectric waveguide and LRSPP waveguide are vertically configured for dense integration and strong coupling. The characteristics of the even and odd super-modes of the coupler are also analyzed to design the device. The fabricated device exhibits damped sinusoidal behavior along the coupling length due to propagation loss of the LRSPP waveguide. The maximum power transfer of 86% from the LRSPP waveguide to the dielectric waveguide is achieved at the coupling length of 600 μm. The measured characteristics of the device are in relatively good agreement with a theoretical analysis.     

基于纳米天线的多通道高强度定向表面等离子体波激发

设计了一种带有纳米天线的金属微腔结构, 以实现高强度表面等离子的定向激发. 在利用双狭缝结构实现表面等离子体波定向激发的基础上, 分别结合共振增强和干涉相长原理, 在传统结构的入射端面上添加纳米天线结构, 并增加狭缝通道数, 实现了定向激发的表面等离子体波的能量增强. 基于纳米天线的多通道高强度定向表面等离子体波激发装置结构简单, 系统紧凑, 并能够有效提高定向传播的表面等离子体波的能量密度和传播距离, 其对微纳光学传输和高密度光学集成领域等方面的研究具有重要意义.     

On the characteristics of commonly nonideal rectangular ridge dielectric-loaded surface plasmon polariton waveguides in practical fabrication processing

In this paper, four commonly nonideal structures of the ideal rectangular dielectric ridge dielectric-loaded surface plasmon polariton waveguides (DLSPPWs) in actual fabrication processing were studied. The mode effective index, propagation length, field distributions, effects of geometric deviation, lateral field confinement and figures of merit of fundamental mode were calculated at the telecommunication wavelengths. It was found that, the propagation length, the lateral field confinement and figures of merit of four nonideal rectangle ridge DLSPPWs were changed compared with the ideal rectangular dielectric ridge DLSPPW. However, the field distributions were kept, and, the characteristics of nonideal rectangle ridge DLSPPWs were affected by the geometric deviation. This study presents the characteristics of commonly nonideal rectangle ridge DLSPPWs and provides substantial information for processing and optimizing the rectangular dielectric ridge DLSPPWs in practical fabrication processing.     

Suppression of radiative losses of surface polaritons on nanostructured thin metal films

The strong electromagnetic coupling between surface plasmon polariton modes on opposite interfaces of a finite thickness periodically nanostructured metal film has been studied. Surface polariton dispersion and associated electromagnetic field distributions have been analyzed. It was shown that at a frequency that corresponds to the crossing of film Bloch modes of different symmetries, the radiative losses of surface polaritons that are related to the polaritons' coupling to light during propagation on the structured surface are suppressed.     

An efficient directional coupling from dielectric waveguide to hybrid long-range plasmonic waveguide on a silicon platform

The silicon-based three-dimensional hybrid long-range plasmonic waveguide not only supports long-range propagation distance (~mm) but also has an ultra-small modal area (~10^?2 μm²) at 1.55 μm. Here, we propose a directional coupler for effective coupling from a dielectric slab-waveguide to the hybrid plasmonic waveguide on a silicon platform. Our simulation results show that the coupler is able to excite hybrid long-range plasmonic mode with short coupling length, low insertion loss, and high extinction ratio. With the arm separation of 0.3 μm, the coupling length can be made 5.2 % of the propagation length of the hybrid plasmonic waveguide, while the insertion loss and extinction ratio are ?0.12 and 22.4 dB, respectively. This coupler offers the potential applications in signal routing between the hybrid long-range plasmonic waveguide and dielectric waveguide in the photonic integrated circuits.     

Propagation constants of guided waves in surface plasmon polariton gap waveguides excited through an I-shaped aperture

The guided waves in the surface plasmon polariton gap waveguide (SPGW) excited by the Gaussian beam through the I-shaped aperture have been investigated by the three-dimensional simulations using a volume integral equation. Optical fields excited in the SPGW are investigated under practical conditions. The complex propagation constants are calculated from the simulated optical fields using the least-squares fitting. The dependence of the propagation constant, i.e., attenuation and phase constants, on the gap-width and on the gap-depth of SPGW is investigated. To cite this article: K. Tanaka et al., C. R. Physique 9 (2008).