Contribution of surface plasmon polaritons to extraordinary optical transmission through metallic nanoslit

A single metallic nanoslit is employed for investigating the contribution of Surface Plasmon Polaritons(SPPs) to Extraordinary Optical Transmission(EOT) based on rigorous electromagnetic theory and the Spectrum Analysis Method(SAM). Numerical results shows that the SPP is the main factor responsible for the EOT, and a phase singularity is observed.

Long-range surface plasmon polaritons with subwavelength mode expansion in an asymmetrical system

Long-range surface plasmon polariton （LRSPP） modes in an asymmetrical system, in which the thin metal film is sandwiched between a semi-infinite substrate and a high permittivity polymer film with a finite thickness, are theoret~ ically calculated and analyzed. Due to the high permittivity of the polymer film, at proper polymer film thicknesses, the index-matching condition of the dielectrics at both sides of the metal can be satisfied for supporting LRSPP modes, and the electromagnetic field above the metal can be localized well. It is found that these LRSPP modes have both long propagation lengths and subwavelength mode expansion above the metal at the optimal polymer film thickncsses. Furthermore, the requirements on the refractive index and the thickness of the polymer film to support LRSPP modes at the optimal thicknesses are found to be not critical.

Open Waveguide Based on Low Frequency Spoof Surface Plasmon Polaritons

A kind of plasmonic open waveguide, which is a periodic subwavelength metallic Domino array, is investigated both theoretically and experimentally in this paper. Based on the guiding mechanism of spoof surface plasmon polaritions (spoof SPPs), the transmission properties of this waveguide are controllable by altering the geometric parameters of the periodic structure. Microwave experimental results verify the high efficiency of wave guiding in such open waveguide, as predicted in theoretic analysis.

Surface plasmon polaritons based optical directional coupler

As a basic optical device, the optical directional coupler (ODC) is basically used as optical splitters, optic switches and so on. A novel ODC employing surface plas- mon polaritons (SPPs) is proposed for high integration. The finite difference time domain (FDTD) method is adopted to simulate and analyze its properties. Results show that the ODC proposed here follows the general regulations of a conventional dielectric ODC, but its transverse size is of nanoscale, which improves the optical integration greatly. For 1550 nm and 1310 nm input wavelengths, when the coupling region length (L) equals half of its coupling length, the Excess Loss is respectively 0.57 dB and 0.56 dB, which is practical in applications. So the research on the present ODC is of some practical importance.

Nanoscale all-optical devices based on surface plasmon polaritons

Surface plasmon polariton,a kind of surface electromagnetic wave propagating along the interface between metals and dielectrics,provides an excellent platform for the realization of integrated photonic devices due to its unique properties of confining light into subwavelength scales.Our recent research progresses of nanoscale integrated photonic devices based on surface plasmon polaritons,including all-optical switches,all-optical logic discriminator,and all-optical routers,are introduced in detail.

On-chip photonic Fourier transform with surface plasmon polaritons

The Fourier transform(FT),a cornerstone of optical processing,enables rapid evaluation of fundamental mathematical operations,such as derivatives and integrals.Conventionally,a converging lens performs an optical FT in free space when light passes through it.The speed of the transformation is limited by the thickness and the focal length of the lens.By using the wave nature of surface plasmon polaritons(SPPs),here we demonstrate that the FT can be implemented in a planar configuration with a minimal propagation distance of around 10 mm,resulting in an increase of speed by four to five orders of magnitude.The photonic FT was tested by synthesizing intricate SPP waves with their Fourier components.The reduced dimensionality in the minuscule device allows the future development of an ultrafast on-chip photonic information processing platform for large-scale optical computing.

The determination of the thickness and the optical dispersion property of gold film using spectroscopy of a surface plasmon in the frequency domain

We propose to use wavelength modulation approach,i.e.,the spectroscopy of a surface plasmon in the frequency domain,to characterize the optical dispersion property of gold film.Using this method,we determine the dispersion relationship of gold film in a wavelength range from 537.12 nm to 905.52 nm,and our results accord well with the reported results by other authors.This method is particularly suited for studying the optical dispersion properties of thin metal films,because a series of dielectric constants over a wide spectral range can be determined simultaneously via only a single scan of the incident angle,thereby avoiding the repeated measurements required when using the angular modulation approach.

Numerical analysis of end-fire coupling of surface plasmon polaritons in a metal-insulator-metal waveguide using a simple photoplastic connector

We propose a design for efficient end-fire coupling of surface plasmon polaritons in a metal-insulator-metal(MIM) waveguide with an optical fiber as part of a simple photoplastic connector. The design was analyzed and optimized using the three-dimensional finite-difference time-domain method. The calculated excitation efficiency coefficient of the waveguide is 83.7%(-0.77 dB) at a wavelength of 405 nm. This design enables simple connection of an optical fiber to a MIM waveguide and highly efficient local excitation of the waveguide.Moreover, the length of the metallic elements of the waveguide, and thus the dissipative losses, can be reduced.The proposed design may be useful in plasmonic-type waveguide applications such as near-field investigation of live cells and other objects with super-resolution.

Surface plasmon polariton waveguides with subwavelength confinement

Surface plasmon polaritons（SPPs） are evanescent waves propagating along metal-dielectric interfaces, which provide an effective way to realize optical wave guiding with subwavelength confinement. Metallic nanostructures supporting SPPs,that is, plasmonic waveguides, are considered as required components to construct nanophotonic devices and circuits with a high degree of miniaturization and integration. In this paper, various types of plasmonic waveguides operating in the visible, infrared, and terahertz regions are reviewed, and the status of the research on their fundamentals, fabrications,and applications is provided as well. First, we discuss the mechanisms of SPPs beyond the diffraction limit, and their launching methods. Then, the characteristics of SPPs on various plasmonic waveguides are reviewed, including top-down and bottom-up fabricated types. Considering applications, certain prototypes of plasmonic devices and circuits constructed by plasmonic waveguides for bio/chemo sensing, router, and light modulation are demonstrated. Finally, a summary and future outlook of plasmonic waveguides are given.

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.

A saccharides sensor developed by symmetrical optical waveguide-based surface plasmon resonance

We proposed a new saccharides sensor developed by symmetrical optical waveguide(SOW)-based surface plasmon resonance(SPR).This unique MgF_(2)/Au/MgF_(2)/Analyte film structure results in longer suface plasmon wave(SPW)propagation lengths and depths,leading to an increment of resolution.In this paper,we managed to decorate the dielectric interface(MgF_(2) layer)by depositing a thin polydopamine film as surface adherent that provides a platform for secondary reactions with the probe molecule.3-Aminophenylboronic acid(3-PBA)is chosen to be the saccharides sense probe molecule in the present work.The aqueous huumnor of Diabetes and Cataract patient whose blood glucose level is normal are analyzed and the results dermonstrated that this sensor shows great potential in monitoring the blood siugar and can be adapted in the field of biological monitoring in the future.

RESEARCH ON WATER QUALITY TESTS BASED ON OPTICAL WAVEGUIDE SURFACE PLASMON RESONANCE TECHNOLOGY

The water quality testing principle by surface plasmon resonance(SPR)is introduced.Using the scanning mode angular spectral testing and the CCD angular spectral testing,a kind of highresolution,wide-range,and portable optical waveguide SPR angular spectral testing system is studied,the method of improving the testing accuracy is discussed,and a long-life surface plasmon optical waveguide transducer is also proposed.Utilizing the SPR testing system,we contrastively tack some test for several sorts of solution,the results presented that significant differences of SPR peaks observed in different sorts of liquid,which indicated the effectiveness of SPR technology used in water quality testing and analysis.

Manipulating surface plasmon waves by transformation optics:Design examples of a beam squeezer,bend,and omnidirectional absorber

We present several design examples of how to apply transformation optics and curved space under coordinate transformation to manipulating the surface plasmon waves in a controlled manner.We demonstrate in detail the design procedure of the plasmonic wave squeezer,in-plane bend and omnidirectional absorber.We show that the approximation method of modifying only the dielectric material of a dielectric-metal surface of the plasmonic device could lead to acceptable performance,which facilitates the fabrication of the device.The functionality of the proposed plasmonic device is verified using three-dimensional full-wave electromagnetic simulations.Aiming at practical realization,we also show the design of a plasmonic in-plane bend and omnidirectional absorber by an alternative transformation scheme,which results in a simple device structure with a tapered isotropic dielectric cladding layer on the top of the metal surface that can be fabricated with existing nanotechnology.

Modified surface plasmonic waveguide formed by nanometric parallel lines

In this paper, two kinds of modified surface plasmonic waveguides formed by nanometric parallel lines are proposed. The finite-difference frequency-domain method is used to study propagation properties of the fundamental mode supported by these surface plasmonie waveguide structures. Results show that the transverse magnetic field of the fundamental mode is mainly distributed in the face to face region formed by two rods. With the same geometrical parameters and the same working wavelength of 632.8 nm, in the case of rods with a triangular cross-section, the degree of localization of field is strong, i.e. the mode area is small, but the fraction of the modal power in the metal increases, so the effective index increases and the propagation length of the mode decreases. With the same geometrical parameters, relative to the case of a working wavelength of 632.8 nm, when working wavelength is large, the mode area of transverse magnetic field distribution is large, i.e. the degree of localization of field is weak, and the interaction of field and silver is weak too, then the effective index decreases, so the propagation length increases. The rounded radii of rods have a great influence on the performance of the surface plasmonic waveguides with rounded triangular cross-sections, but have little influence on the performance of surface plasmonic waveguides with rounded square cross-sections. Since the distribution of transverse magnetic field, effective index, propagation length and the mode area can be adjusted by the geometrical parameters, this kind of modified surface plasmonic waveguide can be applied to the field of photonic device integration and sensors.

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.

Optical Tamm state polaritons in a quantum well microcavity with gold layers

A new type of cavity polariton,the optical Tamm state（OTS） polariton,is proposed to be realized by sandwiching a quantum well（QW） between a gold layer and a distributed Bragg reflector（DBR）.It is shown that OTS polaritons can be generated from the strong couplings between the QW excitons and the free OTSs.In addition,if a second gold layer is introduced into the bottom of the DBR,two independent free OTSs can interact strongly with the QW excitons to produce extra OTS polaritons.

Propagation properties of a modified surface plasmonic waveguide with an arc slot

We introduce a modified surface plasmonic waveguide with an arc slot. The dependences of distribution of energy flux density, effective index, propagation length and mode area of the symmetric mode supported by this waveguide on geometrical parameters and working wavelength are analysed by using the finite-difference frequency-domain （FDFD） method. Results show that the energy flux density distributes mainly in four corners which are formed by two arcs, and the closer to the corners it is, the stronger the energy flux density will be. The effective index, the propagation length and the mode area are influenced by geometrical parameters, including the width, the thickness and the arc radius of the surface plasmonic waveguide, as well as the working wavelength. It has been shown that the surface plasmonic waveguide with an arc slot has better propagation properties than the surface plasmonic waveguide with a straight slot. This work may be helpful for applying the slot surface plasmonic waveguide to integrated photonics.

The surface plasmon polariton dispersion relations in a nonlinear-metal-nonlinear dielectric structure of arbitrary nonlinearity

The analytic surface plasmon polaritons （SPPs） dispersion relation is studied in a system consisting of a thin metallic film bounded by two sides media of nonlinear dielectric of arbitrary nonlinearity is studied by applying a generalised first integral approach. We consider both asymmetric and symmetric structures. Especially, in the symmetric system, two possible modes can exist： the odd mode and the even mode. The dispersion relations of the two modes are obtained. Due to the nonlinear dielectric, the magnitude of the electric field at the interface appears and alters the dispersion relations. The changes in SPPs dispersion relations depending on film thicknesses and nonlinearity are studied.

Compact surface plasmon amplifier in nonlinear hybrid waveguide

Surface plasmon polariton（SPP）, a sub-wavelength surface wave promising for photonic integration, always suffers from the large metallic loss that seriously restricts its practical application. Here, we propose a compact SPP amplifier based on a nonlinear hybrid waveguide（a combination of silver, LiNbO3, and SiO2）, where a couple of Bragg gratings are introduced in the waveguide to construct a cavity. This special waveguide is demonstrated to support a highly localized SPP-like hybrid mode and a low loss waveguide-like hybrid mode. To provide a large nonlinear gain, a pumping wave input from the LiNbO3 waveguide is designed to resonate inside the cavity and satisfy the cavity phase matching to fulfill the optical parametric amplification（OPA） of the SPP signal. Proper periods of gratings and the cavity length are chosen to satisfy the impedance matching condition to ensure the high input efficiency of the pump wave from the outside into the cavity. In theoretical calculations, this device demonstrates a high performance in a very compact scheme（~3.32 μm） and a much lower pumping power for OPA compared with single-pass pumping. To obtain a comprehensive insight into this cavity OPA, the influences of the pumping power, cavity length, and the initial phase are discussed in detail.

Waveguide Mode Splitter Based on Multi-mode Dielectric-Loaded Surface Plasmon Polariton Waveguide

In photonie integrated circuits, information is usually encoded in the optical path. In this work, based on the multi-mode dielectric-loaded surface plasmon polariton waveguide, we numerically design a directional coupler, which can divide the different waveguide eigenmodes into different optical paths. The results show a possibility to encode information onto different waveguide modes. We also experimentally demonstrate that the splitting ratio of this directional coupler structure can be tuned without changing its size.