Self-Phase modulation in nonlinear 2-D plasma waveguides

Pulse propagation equation of 2-D nonlinear dispersion plasma waveguides is strictly educed from the wave equation. The nonlinear coefficient is defined, simplified and used to assess and compare the nonlinear characteristic of three popular 2-D plasma waveguides: the metal stripe, the V-groove on a metal surface and the triangular metal wedge. SPM (Self-Phase Modulation) of three 2-D plasma waveguides is predicted and discussed. The results indicate that the propagation distance is enough to observe SPM phenomenon in 2-D plasma waveguides. Both V-groove and Ag stripe are suitable for constructing nonlinear optical devices.     

Semi-elliptical dielectric-loaded surface plasmon-polariton waveguides

Semi-elliptical dielectric-loaded surface plasmon-polariton waveguide (DLSPPW) is proposed. The mode effective index, field confinement, and propagation length of the fundamental mode supported by it are calculated at the telecom wavelength λ = 1.55 μm for different dimensions of a polymer ridge (with the refractive index of 1.535) placed on a gold film surface. The waveguide structure is found to exhibit 23% increase of the propagation length while showing similar confinement as compared to conventional rectangular DLSPPW when ridge thickness t < 450 nm (ridge width w = 600 nm) and ridge width w < 320 nm (ridge thickness t = 600 nm).     

Hybrid plasmon waveguides with metamaterial substrate and dielectric substrate:A contrastive study

Hybrid plasmon waveguides, respectively, with metamaterial substrate and dielectric substrate are investigated and analyzed contrastively with a numerical finite element method. Basic properties, including propagation length Lp, effective mode area Aeff, and energy distribution, are obtained and compared with waveguide geometric parameters at 1.55 gin. For the waveguide with metamaterial substrate, propagation length Lp increases to several tens of microns and effective mode area Aeff is reduced by more than 3 times. Moreover, the near field region is expanded, leading to potential applications in nanophotonics. Therefore, it could be very helpful for improving the integration density in optical chips and developing functional components on a nanometer scale for all optical integrated circuits.     

Modeling of a surface plasmon polariton interferometer

We model the operation of a micro-optical interferometer for surface plasmon polaritons (SPPs) that comprises an SPP beam-splitter formed by equivalent scatterers lined up and equally spaced. The numerical calculations are carried out by using a relatively simple vectorial dipolar model for multiple SPP scattering [Phys. Rev. B 67 (2003) 165405]. The SPP beam-splitter is simulated elucidating the influence of system parameters, such as the angle of SPP beam incidence, scattering particle size, and inter-particle distance, on the splitting efficiency and phase difference between the transmitted and reflected beams. It is found that the splitting efficiency is very sensitive to the size of scatterers and angle of incidence. Comparing our simulations with experimental data available in the literature, we conclude that this approach can be used, with certain limitations, for modelling of SPP components assembled of individual scatterers, e.g., beam-splitters and interferometers, and suggest further improvements of the model used.     

Superfluid state of coherent light in nonlinear waveguides

We establish the photonic superfluid theory in waveguides made of self-defocussing polar crystals. In quantum theory it is shown that photons can sense an attractive effective interaction by exchange of virtual optical phonons. Such an interaction leads to the photonic superfluid state, in which a propagating photon pair consists of a combination of two photons with opposite transverse wave vector and spins. The most important property of the photonic superfluid state is that the system of photon pairs evolves without scattering attenuations. The traveling-wave superfluid state has the squeezing property and the soliton effect.     

The optical transmission characteristics through gold nanoslit arrays embedded in nonlinear medium

We present the numerical investigation of the optical transmission through a periodic gold nanoslit array embedded in the Kerr type nonlinear medium by using a developed two-dimensional Finite Different Time Domain (FDTD) method. The enhanced transmission in the nonlinear structure is attributed to the collaboration of the surface plasmon resonance and the localized waveguide resonance. We show that, in a certain intensity range, with the increase of the incident intensity, the transmission resonance peaks redshift obviously, and peak values decrease firstly and then increase; with the gold film thickness and the embedded depth becoming larger, transmission resonance peaks of both types redshift significantly, and the peak number, peak value and the half peak width change obviously. The electric fields distributions for different embedded depths of the gold slits at various resonance wavelengths are simulated to illuminate the underlying physical mechanisms. It is expected that these results obtained here will help to design nonlinear subwavelength metallic grating devices.     

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.     

About the nature of increase of the nonlinear optical response of a rough surface

It is shown that during the propagation of surface plasmon polariton (SPP) in the system of two touching spheres (or cones) when one is a metal and the other is a semiconductor, the conditions of strong localization of the surface wave are realized. At the point of contact, an essential decrease of the wavelength of the SPP is observed and the diffraction processes do not hinder its localization on the nanometric scale. As a result, wave fields increase anomalously. The considered phenomena open a new possibility to propose the experimental way for exploring the gigantic enhancement of the nonlinear optical response from a rough surface.     

Photonic bandgap structures for long-range surface plasmon polaritons

Propagation of long-range surface plasmon polaritons (LR-SPPs) along periodically thickness-modulated metal stripes embedded in dielectric is studied both theoretically and experimentally for light wavelengths in the telecom range. We demonstrate that symmetric (with respect to the film surface) nm-size thickness variations result in the pronounced band gap effect, and obtain very good agreement between measured and simulated (transmission and reflection) spectra. This effect is exploited to realize a compact wavelength add-drop filter with the bandwidth of 20 nm centered at 1550 nm. The possibilities of achieving a full bandgap (in the surface plane) for LR-SPPs are also discussed.     

Energy transport in plasmon waveguides on chains of metal nanoplates

An interest in energy transport in 3D chains of metal nanoparticles is oriented towards future applications in nanoscale optical devices. We consider plasmonic waveguides composed of silver nanoplates arranged in several geometries to find the one with the lowest attenuation. We investigate light propagation of 500-nm wavelength along different chains of silver nanoplates of subwavelength length and width and wavelength-size height. Energy transmission of the waveguides is analysed in the range of 400–2000 nm. We find that chain of short parallel nanoplates guides energy better than two electromagnetically coupled continuous stripes and all other considered nonparallel structures. In a wavelength range of 500–600 nm, this 2-μm long 3D waveguide transmits 39% of incident energy in a channel of λ × λ/2 cross section area.     

Temperature dependence of symmetric and asymmetric structured Au stripe waveguides

The thermal effects on pigtailed 22-nm-thick, 5-μm-wide and 1-cm-long Au stripe long-range surface plasmon polariton (LRSPP) waveguides, embedded in polymer/polymer layers and in polymer/silica layers, are theoretically and experimentally demonstrated. The polymer and silica cladding layers have thermo-optic coefficients of opposite signs. As the temperature varies the Au stripe LRSPP waveguide embedded in the polymer/polymer layers retains its symmetry in the refractive index, but that embedded in the polymer/silica layers becomes asymmetric in the refractive index. The thermal sensitivity in the optical output power of the symmetric structure is smaller than 0.02 dB/°C but the sensitivity of the asymmetric structure is ∼ 0.3 dB/°C. These structures open up potential applications of the LRSPP waveguides for temperature independent/dependent photonic devices.     

Spatial solitons in nonlinear liquid waveguides

Spatial solitons are studied in a planar waveguide filled with nonlinear liquids. Spectral and spatial measurements for different geometries and input power of the laser beam show the influence of different nonlinear effects as stimulated scatterings on the soliton propagation and in particular on the beam polarization. The stimulated scattering can be used advantageously to couple the two polarization components. This effect can lead to multiple applications in optical switching.     

Numerical analysis of surface plasmon nanocavities formed inthickness-modulated metal－insulator－metal waveguides

The enhancement characteristics of the local field in the surface plasmon nanocavities are investigated numerically. The cavity is constructed by placing a defect structure in the thickness-modulated metal--insulator--metal waveguide Bragg gratings. The characteristic impedance based transfer matrix method is used to calculate the transmission spectra and the resonant wavelength of the cavities with various geometric parameters. The finite-difference time-domain method is used to obtain the field pattern of the resonant mode and validate the results of the transfer matrix method. The calculation and simulation results reveal the existence of resonant wavelength shift and intensity variation with structural parameters, such as the modulation period of the gratings, the length and the width of the defect structure. Both numerical analysis and theoretical interpretation on these phenomena are given in details.     

Magneto-optic phase shift in plasmon propagation along garnet/semiconductor-on-insulator structures

This paper discusses the magneto-optic phase shift in garnet/semiconductor-on-insulator plasmonic waveguides. We consider two structures: (1) Y IG/Si/SiO₂ and (2) Y IG/GaInAsP/AlInAs-oxide. A dispersion relation for the plasmon propagation has been derived and the nonreciprocal phase shift of the fundamental TM mode has been determined at wavelengths of 1.55 μm, 1.5 μm and 1.3 μm.     

Tunable local surface plasmon resonance in liquid-crystal-coated Ag nanoparticles

The far-field and near-field properties of a spherical nematic liquid crystal (NLC) coated metal nanoparticle (NPs) have been investigated in an external field, basing on the quasistatic theory. The resonant wavelength is tunable by varying metallic material of core, anisotropy extent and thickness of liquid crystals (LCs). The field enhancement is along the incident polarization near the outer surface of the shell. The direction of field is reverse in the inner surface comparing with the one if outer shell. In contrast to isotropy shell, the surface plasmon resonance (SPR) shows an obvious red shift and field enhancement near outer surface of the shell always is stronger.     

Polarization controlled couplings of surface plasmon with asymmetrical nanoslit pairs

Light-driven surface plasmons offer an opportunity to ultrafast information processing combining the compactness of electric circuits with the bandwidth of photonic networks. For practical applications, the efficient and controllable conversion from signal light to surface plasmons is essential. This leads to the recent developments in the polarization controlled couplings of surface plasmons. Currently, most works only tailor the orientation and arrangement of nanoslits to control the launching of surface plasmons. In this paper, we consider both the orientation and size of each slit in a one-dimensional array of nanoslit dimers. We first realize the unidirectional propagation of surface plasmons with designed wavefronts. Next, the unidirectional coupling and bi-directional coupling of surface plasmons are realized for a pair of orthogonal polarizations, respectively. This is quite different from the conventional opposite propagating surface plasmons excited by two orthogonal polarizations. The manipulation of both orientation and size of nanoslits allows additional freedom in the photon-plasmon conversions.     

各向异性特异材料波导中表面等离子体的共振性质

使用时域有限差分法,研究了各向异性特异材料(AMM)作为包层的AMM/介质/AMM波导中表面等离子体的共振性质.色散关系表明,当特异材料为负磁导率的always-cutoff型时,AMM/介质/AMM波导支持TE极化的表面等离子体,表面等离子体的波长随着中间介质层的厚度和特异材料磁等离子体频率的减小而变短.在有限长度AMM/介质/AMM波导中,由于两端界面的反射,表面等离子体模在波导中形成Fabry-Perot共振,而实现亚波长的表面等离子体微腔.在共振频率,电场强度在微腔的中部达到最大值,而磁场分别在两端界面处达到最大,电磁能强局域在中间介质层中,这一性质将在可调的具有强局域特性的亚波长微腔及腔量子电动力学中具有潜在的应用.     

Experimental study of solitary waves in a nonlinear transmission line

Several properties of solitary waves were measured on a nonlinear transmission line. These include the transition from a linear dispersive response into a solitary wave response as the amplitude of a narrow voltage impulse is increased, and an observation of the recurrence phenomena of solitary waves. Supported in part by the National Science Foundation.     

Periodic waves in nonlinear metamaterials

Periodic waves are presented in this Letter. With symbolic computation, equations for monochromatic waves are studied, and analytic periodic waves are obtained. Factors affecting properties of periodic waves are analyzed. Nonlinear metamaterials, with the continuous distribution of the dielectric permittivity obtained, are different from the ones with the discrete distribution.     

A theoretical study of surface plasmon cross coupling in asymmetric corrugated metal films

We investigate numerically the transmission properties of a thin sinusoidally corrugated metal film bounded by two different dielectrics in the context of the experiment of Gruhlkeet al (1986). We study the dominant contributions from both the propagating and evanescent plane waves. A comparison with the experimental results reveals that the decisive role in cross coupling is played by the evanescent waves emitted by the molecular dipole. We extend our studies to different corrugation amplitudes and widths to show their effect on transmission.