Surface plasmon polaritons on narrow-ridged short-pitch metal gratings in the conical mount

Recent investigations into high-aspect-ratio short-pitch metal grating structures have shown that it is possible to excite surface plasmon polaritons (SPPs) even in the zero-order region of the spectrum. The predominant reason this is possible is that extremely large bandgaps occur in the SPP dispersion curves, which are caused by the large depths, and heights, of the structures. The form of the resultant dispersion curves has also been found to be highly dependent on the shape of the grating profile. We present an extension to a previously published paper that described the nature of the SPPs excited on narrow-ridged short-pitch metal gratings in the classical mount by considering the case in which the radiation is incident at nonzero azimuthal angles (the conical mount). In particular, we consider the case of 90 degrees and 45 degrees azimuthal angles and discuss the coupling to the SPP modes and the way in which polarization conversion is evident on such structures.     

Surface plasmon polaritons at the interface of form birefringence metal and the negative magnetic permeability material

The surface plasmon polaritons (SPPs) at the interface of form birefringence metal (FBM) and the negative magnetic permeability material (NMPM) are investigated. The dispersion relation and the characteristic length of the p- and s-polarized SPPs along the X and Y directions are discussed in detail, including the wavelength, the propagation distance, and the penetration depth into two media of SPPs in the range of 400–600?nm. It is shown that both p- and s-polarized SPPs can be observed at the interface formed by FBM and NMPM, and that their properties and characteristic length are very different along the X and Y directions. Especially, it is also found the maximum and minimum of characteristic length for the p- and s-polarized SPPs at certain wavelength.     

Controlling surface plasmon polaritons in transformed coordinates

Transformational optics allows for a markedly enhanced control of the electromagnetic wave trajectories within metamaterials, with interesting applications ranging from perfect lenses to invisibility cloaks, carpets, concentrators and rotators. Here we present a review of curved anisotropic heterogeneous meta-surfaces designed using the tool of transformational plasmonics, in order to achieve a similar control for surface plasmon polaritons in cylindrical and conical carpets (for the latter we provide some analytical insight), as well as cylindrical cloaks, concentrators and rotators of a non-convex cross-section. Finally, we provide an asymptotic form of the geometric potential for surface plasmon polaritons on such surfaces in the limit of a small curvature.     

Observation of stimulated emission of surface plasmon polaritons

We report a direct experimental evidence of stimulated emission of surface plasmon polaritons (SPPs) at telecom wavelengths (1532 nm) with erbium doped glass as a gain medium. We observe an increase in the propagation length of signal surface plasmons when erbium ions are excited optically using pump SPP. The design, fabrication, and characterization of SPP waveguides, thin gold metal strips, embedded in erbium (Er) doped phosphate glass is presented. Such systems can be suitable as integrated devices coupling electronic and photonic data transmissions as well as SPP amplifiers and SPP lasers.     

Nano-holes in silicon wafers using laser-induced surface plasmon polaritons

Surface Plasmon Polaritons (SPPs) have been explored for a multitude of applications including sub-wavelength lithography, data storage, microscopy and photonics. In this paper, we report the use of SPPs for nanomachining silicon in massively parallel fashion. A Q-switched Nd:YAG laser beam was impinged on gold-thin film deposited, porous alumina membrane (PAM) that contains periodic 2-D array of thousands of nano-holes. The silicon substrate was placed in close proximity with PAM. The formation of SPPs and their coherent interference at the exit of PAM holes created strong nanoscale electrical fields which in turn produced 50-70 nm diameter holes in silicon.     

Adiabatic description of superfocusing of femtosecond plasmon polaritons

A surface plasmon polariton is a collective oscillation of free electrons at a metal–dielectric interface. As wave phenomena, surface plasmon polaritons can be focused with the use of an appropriate excitation geometry of metal structures. In the adiabatic approximation, we demonstrate a possibility to control nanoscale short pulse superfocusing based on generation of a radially polarized surface plasmon polariton mode of a conical metal needle in view of wave reflection. The results of numerical simulations of femtosecond pulse propagation along a nanoneedle are discussed. The space–time evolution of a pulse for the near field strongly depends on a linear chirp of an initial laser pulse, which can partially compensate wave dispersion. The field distribution is calculated for different metals, chirp parameters, cone opening angles and propagation distances. The electric field near a sharp tip is described as a field of a fictitious time-dependent electric dipole located at the tip apex.     

Wavelength selective nanophotonic components utilizing channel plasmon polaritons

We fabricate and investigate wavelength selective components utilizing channel plasmon polaritons (CPPs) and operate at telecom wavelengths: a waveguide-ring resonator-based add-drop multiplexer (WRR-ADM) and a compact (3.75-microm-long) Bragg grating filter (BGF). The CPP waveguides represent 0.5-microm-wide and 1.3-microm-deep V-grooves in gold, which are combined with a 5-microm-radius ring resonator (in the WRR-ADM) or 0.5-microm-long wells milled with the period of 0.75 microm across a groove (in the BGF). The CPP-based components are characterized in the wavelength range of 1425-1600 nm by use of near-field optical microscopy, exhibiting the wavelength selectivity of approximately 40 nm.     

Surface energy driven agglomeration and growth of single crystal metal wires

We introduce a novel wire growth technique that involves simply heating a multilayer film specifically designed to take advantage of the different surface energies of the substrate and film components. In all cases the high surface energy component is extruded as a single crystal nanowire. Moreover we demonstrate that patterning the bilayer film generates localized surface agglomeration waves during the anneal that can be exploited to position the grown wires. Examples of Au and Cu nanowire growth are presented, and the generalization of this method to other systems is discussed.     

Grating-coupled surface plasmon polaritons and waveguide modes in a silver-dielectric-silver structure

A silver-dielectric-silver structure that supports both waveguide modes and surface plasmon polaritons is explored. The upper interface between the dielectric and the silver is periodically corrugated to allow coupling of visible photons to both types of mode. Such a metallic microcavity leads to plasmonic and waveguide self-interacting bandgaps at Brillouin zone boundaries. In addition there are found other bandgaps from mode crossings within the Brillouin zone. This results specifically in a very flat photonic band due to anticrossings between a surface plasmon polariton and waveguide modes. Characterization of the observed modes in terms of their resonant electromagnetic fields is achieved by using a multilayer, multishape differential grating theory.     

Quantum statistics of surface plasmon polaritons in metallic stripe waveguides

Heralded single surface plasmon polaritons are excited using photons generated via spontaneous parametric down conversion. The mean excitation rates, intensity correlations, and Fock state populations are studied. The observed dependence of the second-order coherence in our experiment is consistent with a linear uncorrelated Markovian environment in the quantum regime. Our results provide important information about the effect of loss for assessing the potential of plasmonic waveguides for future nanophotonic circuitry in the quantum regime.     

Optical bistability of surface plasmon polaritons in nonlinear Kretschmann configuration

Optical bistability based on surface plasmon polaritons in the Kretschmann configuration involving a Kerr nonlinear medium is described by analytical solutions. The conditions of forming the optical bistability with different parameters are explored. The resonant angle of surface plasmon polaritons varying with the incident light intensity also generates the phenomenon of bistability. The system could form optical bistability with the special thickness of the metal film and incident angle. This kind of system has potential application in all-optical networks.     

Strong resonant coupling of surface plasmon polaritons to radiation modes through a thin metal slab with dielectric gratings

Strong resonant coupling of surface plasmon polaritons to radiation modes by means of a dielectric grating deposited on top of a metal slab is numerically analyzed, and some novel properties of this configuration are discussed. The dielectric grating is not only responsible for coupling of incident light to surface plasmon polaritons but also for outcoupling of the surface plasmon polaritons to radiation modes. A key advantage of the configuration presented is that it is not based on conventional attenuated total reflection using a prism with high refractive index.     

Near-field visualization of strongly confined surface plasmon polaritons in metal-insulator-metal waveguides

A nanoscale gap between two metal surfaces can confine propagating surface plasmon polaritons (SPPs) to very small dimensions, but this geometry makes it inherently difficult to image SPP propagation at high resolution. We demonstrate the near-field probing of these SPPs, propagating within a 50 nm thick Si 3N 4 waveguide with Ag cladding layers for frequencies ranging from the blue to the near-infrared. Using near-field SPP interferometry, we determine the wave vector, showing that the wavelength is shortened to values as small as 156 nm for a free-space wavelength of 532 nm.     

Amplified spontaneous emission of surface plasmon polaritons with unusual angle-dependent response

Loss issues are fundamentally crucial for the application of surface plasmon polaritons (SPPs). In this study the amplified spontaneous emission (ASE) of SPPs in a typical Kretschmann configuration is observed and shows an unusually broadened angular response with increased pump intensity. Theoretical models are further developed to verify the results and understand the amplification of SPPs in Fourier space.     

Surface plasmon interference nanolithography

A new nanophotolithography technique based on the interference of surface plasmon waves is proposed and demonstrated by using computer simulations. The wavelengths of the surface plasmon waves at metal and dielectric interfaces can reach the nanometer scale while their frequencies remain in the optical range. As a result, the resolution of this surface plasmon interference nanolithography (SPIN) can go far beyond the free-space diffraction limit of the light. Simulation results show that one-dimensional and two-dimensional periodical structures of 40-100 nm features can be patterned using interfering surface plasmons launched by 1D gratings. Detailed characteristics of SPIN such as field distribution and contrast are also investigated.     

Launching propagating surface plasmon polaritons by a single carbon nanotube dipolar emitter

We report on the excitation of propagating surface plasmon polaritons in thin metal films by a single emitter. Upon excitation in the visible regime, individual semiconducting single-walled carbon nanotubes are shown to act as directional near-infrared point dipole sources launching propagating surface plasmons mainly along the direction of the nanotube axis. Plasmon excitation and propagation is monitored in Fourier and real space by leakage radiation microscopy and is modeled by rigorous theoretical calculations. Coupling to plasmons almost completely reshapes the emission of nanotubes both spatially and with respect to polarization as compared to photoluminescence on a dielectric substrate.     

In situ generation of surface plasmon polaritons using a near-infrared laser diode

We demonstrate a semiconductor laser-based approach which enables plasmonic active devices in the telecom wavelength range. We show that optimized laser structures based on tensile-strained InGaAlAs quantum wells-coupled to integrated metallic patternings-enable surface plasmon generation in an electrically driven compact device. Experimental evidence of surface plasmon generation is obtained with the slit-doublet experiment in the near-field, using near-field scanning optical microscopy measurements.     

Enhanced effect of local fields in subwavelength metallic series nanocavities from surface plasmon polaritons

The enhancement and confinement characteristics of the local field in the two-dimensional (2D) subwavelength-size series cavities structure are investigated numerically by using the boundary integral method. The series cavities are built of two pieces of finite silver thin slabs with subwavelength corrugations on their inner boundaries, set in a face-to-face arrangement with a separating space, and the central part is a narrow channel (NC). We calculate the average amplitude of the local field in the NC as a function of the wavelength for exploring the influence of the structural parameters and demonstrate the amplitude distribution of the magnetic field in the structure and the cross-section distributions of the local field in the NC region along both the longitudinal axis direction and the transverse directions. The simulations show that the local field in the NC has significant enhancement, up to 2 orders of magnitude, of the incident light field, and the local light field is confined to a small region less than one fifth of the resonant wavelength in the longitudinal direction and one twentieth of the resonant wavelength in the lateral direction. Replacing the metallic material of the cavity walls with the semiconductor germanium leads to the complete disappearance of the enhancement of the local field. It is clearly shown that surface plasmon polaritons on the metal play a critical role for this enhancement phenomenon. The influences of various geometric parameters on the resonant wavelength and the peak value of the average amplitude of the local field are extensively investigated.     

Surface plasmon resonance near-infrared spectroscopy

Near-infrared (NIR) spectroscopy is ill-suited to microanalysis because of its low absorptivity. We have developed a highly sensitive detection method for NIR spectroscopy based on absorption-sensitive surface plasmon resonance (SPR). The newly named SPR-NIR spectroscopy, which may open the way for NIR spectroscopy in microanalysis and surface science, is realized by an attachment of the Kretschmann configuration equipped with a mechanism for fine angular adjustment of incident light. The angular sweep of incident light enables us to make a tuning of a SPR peak for an absorption band of sample medium. From the dependences of wavelength, incident angle, and thickness of a gold film on the intensity of the SPR peak, it has been found that the absorbance can be enhanced by approximately 100 times compared with the absorbance obtained without the gold film under optimum conditions. This article reports the details of the experimental setup and the characteristics of absorption-sensitive SPR in the NIR region, together with some experimental results obtained by using it.     

Periodical concentration of surface plasmon polaritons by wave interference in metallic film with nanocavity array

Metallic thin films with nanocavity arrays provide ideal platforms for plasmonics, non-linear optics, surface chemistry and corresponding applications. A general understanding of electromagnetic (EM) field distributions is needed for further creation, manipulation and designation of near-field enhancements. Herein, we study the distribution of plasmonic hot spots over Ag thin films with triangular nanocavities in hexagonal arrays with a variable of lattice parameters. We propose that the concentration and interference of surface plasmon polaritons (SPP) dominates the distribution of plasmonic hot spots. The localized surface plasmonic resonance (LSPR) at nanocavities excites SPPs to propagate on the thin film, whose concentration and interference lead to an extremely strong near-field enhancement at the surface of the thin film, the location of which can also be termed as plasmonic hot spot. For this model, the calculation results of the physical formula are in excellent agreements with both the experimental results and the electrodynamic simulations with 3D finite element method (FEM). Moreover, the plasmonic hot spots distribute periodically within the nanocavity arrays, determined by the geometric symmetry of the array as well as with the polarization state of the incident field. The periodicity of plasmonic hot spots on flat surface illustrates a new way to concentrate SPPs in an extendable area, which has potential applications in localized non-linear optics, sensing, plasmonic logical circuit and optical computing.