Excitation Of Surface Plasmon Polaritons Research Articles

Tunable plasmonics photodetector in near-infrared wavelengths using graphene chemical doping method

Graphene-based photodetectors have been caught in the spotlight of optoelectronics devices and they are significant candidates for tunable detectors. Unfortunately, little reports are presented for absorption enhancement in near-infrared range. Therefore, here, a graphene-based photodetector with plasmonic structure consisting of Silicon and SiO2 substrate, graphene layer, and metal nano-grating in near-infrared range is proposed. The optical absorption of graphene layer in this structure increases due to the occurrence of plasmonic effects and excitation of surface plasmon polaritons (SPPs) in metal and graphene interface. The optical response of the proposed structure is numerically simulated using the finite-difference time-domain (FDTD) method. To optimize the optical absorption of the structure, the effects of geometrical parameters, the chemical potential of graphene, the number of graphene layers, and the incident angle have been investigated. Based on numerical results, the absorption of monolayer graphene enhanced from 0.023 to nearly 0.70, even to a maximum value of 0.80 in three-layer graphene and the total absorption of optimized structure reached to about 0.98 at telecommunication wavelength (1.55 μm). Moreover, the absorption spectrum of the proposed structure can be tuned by either changing the geometrical parameters of nano-grating or chemical potential of graphene.

Plasmon-Assisted Direction- and Polarization-Sensitive Organic Thin-Film Detector.

Utilizing Bragg surface plasmon polaritons (SPPs) on metal nanostructures for the use in optical devices has been intensively investigated in recent years. Here, we demonstrate the integration of nanostructured metal electrodes into an ITO-free thin film bulk heterojunction organic solar cell, by direct fabrication on a nanoimprinted substrate. The nanostructured device shows interesting optical and electrical behavior, depending on angle and polarization of incidence and the side of excitation. Remarkably, for incidence through the top electrode, a dependency on linear polarization and angle of incidence can be observed. We show that these peculiar characteristics can be attributed to the excitation of dispersive and non-dispersive Bragg SPPs on the metal–dielectric interface on the top electrode and compare it with incidence through the bottom electrode. Furthermore, the optical and electrical response can be controlled by the organic photoactive material, the nanostructures, the materials used for the electrodes and the epoxy encapsulation. Our device can be used as a detector, which generates a direct electrical readout and therefore enables the measuring of the angle of incidence of up to 60° or the linear polarization state of light, in a spectral region, which is determined by the active material. Our results could furthermore lead to novel organic Bragg SPP-based sensor for a number of applications.

Electrical Dynamic Switching of Magnetic Plasmon Resonance Based on Selective Lithium Deposition.

Active plasmonic nanostructures have garnered considerable interest in physics, chemistry, and material science due to the dynamically switchable capability of plasmonic responses. Here, the first electrically dynamic control of magnetic plasmon resonance (MPR) through structure transformation by selective deposition of lithium on a metal-insulator-metal (MIM) structure is reported. Distinct optical switching between MPR and surface plasmon polariton (SPP) excitations can be enabled by applying a proper electrical current to the electrochemical cell. Furthermore, the structure transformation through lithium metal deposition indicates the reconfigurable MPR excitation in a full cycling of the charging and discharging process. The results may shed light on electrically compatible self-powered active plasmonics as well as nondestructive optical sensing for electrochemical evolution.

Optical activity and excitation of surface plasmon polaritons with electromagnetically induced chiral media

Chiral materials possess some unusual properties for which they have attracted tremendous interest in recent research. In this paper, we discuss the interaction of electromagnetic fields with an initially isotropic material, making it anisotropic chiral by inducing magnetoelectric cross coupling. We consider a four-level double Λ -type configuration of an atomic ensemble, which is simultaneously sensitive to relative phase of the applied fields due to its closed-loop nature, providing an extra degree of freedom for controlling the birefringent nature of the medium. We show that the material splits a linearly polarized probe field into left- (LCP) and right-circularly polarized (RCP) components, and their angular divergence can be related to the optical activity of the medium. This leads to efficient modulation of the probe field, which may be helpful in accurate position detection of the transmitted beams and images. Next, we demonstrate that such a medium can be used to couple incident light with surface plasmons (SPs) in two ways: (1) as a prism-like coupler, in either Otto- or Kretschmann-type geometry, where excitation of SPs can be achieved beyond a certain incident angle of the interacting pulse in a plasmonic waveguide placed closed to it; and (2) direct excitation of SPs by a LCP or RCP beam from the chiral medium in a particular slit-type plasmonic waveguide. We find that the coupled modes in the latter case are unidirectional and highly tunable. Further, we show that the birefringent nature of the medium as well as the plasmonic field intensities can be efficiently manipulated with a number of controlling parameters. Our results may find applications in image coding, plasmonic sensors, and bio-photonics.

Impact of Surface Plasmon Polaritons on Silver Photodiffusion into As2S3 Film

The effect of the surface plasmon polariton excitation at the silver–chalcogenide glass interface on the photostimulated diffusion of silver into chalcogenide was studied. The test sample was a two-layer Ag–As2S3 structure deposited on the diffraction gratings with a 899-nm period made using interference photolithography. Photostimulated changes were registered by measuring the kinetics and the angular dependences of the specular reflection of the 632.8-nm wavelength p-polarized light. It was found that the process of photostimulated diffusion of silver into the chalcogenide layer significantly accelerates at its initial stage when the surface plasmon polariton is excited at the Ag–As2S3 interface during irradiation. Thus, it promotes the increase in photosensitivity of the structure—when irradiated at an angle corresponding to the excitation of the plasmon, the entire photodoping process completes much faster.

Optical Effects in Magnetoplasmonic Crystals Based on 1D Metal-Dielectric Lattice

Properties of one-dimensional spatially periodic metal structures formed by a dielectric lattice covered by gold and permalloy films are studied by optical and magnetooptical spectroscopy techniques. It is shown that these structures reveal the excitation of surface plasmon-polaritons, with the resonance frequency that can be controlled by the geometry of the experiment. The magnetooptical Kerr effect modulation, which is absent in the case of a nonprofiled gold/permalloy bifilm, is observed in the spectral vicinity of the plasmon resonance.

Unidirectional propagation of electrically driven surface plasmon polaritons: a numerical study

Electrically excited surface plasmon polaritons (SPPs) created, for instance, through the energy loss from inelastic electron tunneling, have received great interest recently because of their potential for facilitating the integration of on-chip information processing elements. Consequently, finding a convenient method of realizing the propagation control of such a kind of SPPs becomes a valuable research topic. Optical antennas array, with a relatively large footprint, are commonly used for steering SPPs. In this paper, with the aid of two plasmonic strip-type antennas that are placed next to each other, we present a feasible method of propagation control of electrically driven SPPs in a scanning tunneling microscope (STM) system. Results show that STM-induced SPPs propagate along a preferred direction due to the in-plane SPP interference effects, which can be easily engineered by the widths of the antennas. This result is very useful for compact plasmonic circuits design.

Significant enhancement of near-field radiative heat transfer between black phosphorus-covered hyperbolic metamaterial

Hyperbolic metamaterial, a novel type of anisotropic bulk material, can enhance the near-field radiation heat transfer (NFRHT) via supporting unbounded hyperbolic phonon polaritons (HPPs). A cutting-edge two-dimensional material, black phosphorous (BP), also gives a rise to promising performance in the NFRHT due to its excitation of surface plasmon polaritons (SPPs). Here, by coupling SPPs with HPPs, we have proposed a hybrid heterostructure that consists of a single top-covered BP layer with doped-Si nanowire arrays (D-SiNWs) and explored the NFRHT between two heterostructures separated by a vacuum gap. The hybrid heterostructure enables a significant enhancement of NFRHT contributed to the excited hybridized modes of BP plasmons and HPPs. The SPPs of BP expand the effective range of HPPs to the high-k space, resulting in a heat transfer coefficient that is 2.9 times and 1.7 times larger than that of two D-SiNWs and two monolayer BPs, respectively. Influences of electron density of BP are conclusively clarified from the profile of the plasma dispersion relation. Thus, it is expected that the proposed configuration can be used to regulate the near-field heat transfer in a tunable fashion and shed light on an invaluable technique toward the design of two-dimensional materials for thermal and electrical applications.

Self-Organized Nanogratings for Large-Area Surface Plasmon Polariton Excitation and Surface-Enhanced Raman Spectroscopy Sensing

Surface plasmon polaritons (SPP) are exploited due to their intriguing properties for the fabrication and miniaturization of photonic circuits, for surface-enhanced spectroscopy and imaging beyond the diffraction limit. However, excitation of these plasmonic modes by direct illumination is forbidden by energy/momentum conservation rules. One strategy to overcome this limitation relies on diffraction gratings to match the wavevector of the incoming photons with that of propagating SPP excitations. The main limit of the approaches so far reported in the literature is that they rely on highly ordered diffraction gratings fabricated by means of demanding nanolithographic processes. In this work, we demonstrate that an innovative, fully self-organized method based on wrinkling-assisted ion-beam sputtering can be exploited to fabricate large-area (cm2 scale) nanorippled soda lime templates, which conformally support ultrathin Au films deposited by physical deposition. The self-organized patterns act as quasi-one-dimensional (1D) gratings characterized by a remarkably high spatial order, which properly matches the transverse photon coherence length. The gratings can thus enable the excitation of hybrid SPP modes confined at the Au/dielectric interfaces, with a resonant wavelength that can be tuned by modifying the grating period, photon incidence angle, or, potentially, the choice of the thin-film conductive material. Surface-enhanced Raman scattering experiments show promising gains in the range of 103, which are competitive, even before a systematic optimization of the sample fabrication parameters, with state-of-the art lithographic systems, demonstrating the potential of such templates for a broad range of optoelectronic applications aiming at plasmon-enhanced photon harvesting for molecular or biosensing.

Excitation of odd-mode spoof surface plasmon polaritons and its application on low-pass filters

Dispersion properties of compact single- and double-side grooves SSPPs are analyzed and compared. The combination of two single-side grooves with opposite phases can sustain the odd-mode SSPPs, which is contrary to the dominantly even mode SSPPs existed on metal-dielectric interfaces in optical frequencies or on structured metal surfaces in the lower frequencies. Two low-pass filters based on odd-mode SSPPs working at 0–7 and 0–14.1 GHz are fabricated and measured. Both simulations and measurements validate that the proposed SSPPs structure can realize high-efficiency excitation of odd-mode SSPPs and low-loss transmission properties.

Ultrathin, polarization-insensitive multi-band absorbers based on graphene metasurface with THz sensing application

This article presents multi-band plasmonic absorbers based on a graphene array at terahertz frequencies. The absorbers are made of a very simple structure including a graphene disk array printed on the top surface of a dielectric spacer backed by a metallic ground plane. Multi-band performance is achieved with more than 90% absorption in the 1–8 THz frequency range by exciting surface plasmon polaritons of graphene. It is shown that the resonance frequencies of the proposed absorber can be tuned by varying the chemical potential between 0.8–1 eV for a triple-band absorber and 0.7–0.9 eV for a quad-band one, while keeping more than 80% absorption. The results obtained by means of full-wave simulation are verified with the results obtained by the analytical circuit model. The proposed absorbers are polarization-insensitive and provide stable absorption performance for both of the TE and TM polarizations. As an application, we designed a refractive index sensor based on the triple-band absorber. The results verify that the absorption bands are sensitive to the variations of the refractive index of the coating layer.

Optical alignment of achiral nanoparticles via the use of induced chiral force

A chiral force was found to be induced upon rotation of planar nanoparticles under irradiation of linearly polarized light. The chiral force arises due to differing absorptions of left and right circularly polarized light, correlating with the circular dichroism (CD) of rotated nanoparticle. Charge distribution profiles, which arises from the excited localized surface plasmon polaritons induced by the light, can be used to predict the CD. This offers a simple method of using charge distributions to predict the dynamics of nanoparticles for optical alignment and orientation in the fabrication of various optical devices.

Novel Au nano-grating for detection of water in various electrolytes

This paper reports an advanced and novel sensing idea by utilizing the concept of surface plasmon resonance. A numerically designed model of plasmonic-based sensor has been proposed that is capable of detecting the mixture of water in alcohol and in a variety of other electrolytes including milk, hemoglobin, octane, etc. The sensor uses gold as a recognition element with equidistant slits for the transmission of incoming light which give rise to plasmon polaritons on metal–dielectric–interface. The zeroth-order transmission spectra have been extracted for this investigation and optimization. A transverse magnetic wave illuminates the noble metal normally through a glass substrate generating surface plasmon polaritons (SPPs) on a particular wavelength which changes with respect to the refractive index of adjacent medium. The sensor model has been numerically solved after optimization of slit size by keeping other parameters fixed utilizing the fundamental plasmonic mode for efficient excitation of SPPs. In this sensing chip, a uniform spatial period of about 660 nm, a constant slit size of 320 nm, a gold thickness of 50 nm for sensing element and 500 nm for glass substrate are used. An appreciable increment in the value of refractive index sensitivity of 668.66 nm per RIU has been found which is noteworthy. Such sensors are likely been welcomed in biological investigation, along with chemical and environmental detection techniques.

Surface plasmon-polariton waves guided by an interface of a metal and an obliquely mounted uniaxially chiral, bianisotropic material

ABSTRACT The excitation of surface plasmon-polariton (SPP) waves was delineated for an interface of a metal and an obliquely mounted uniaxially chiral, bianisotropic material with optic axis making an arbitrary angle with the interface plane. Such a material can be fabricated as a parallel assembly of hellixes with the axis of the hellixes making an arbitrary tilt angle with the metallic substrate. The canonical boundary-value problem as well as the two prism-coupled configurations were investigated. The direction of propagation of SPP waves was restricted to be in the morphologically significant plane of the bianisotropic material that contains titled hellixes. It was found that the chirality parameter of the bianisotropic material has to have a magnitude smaller than a threshold in order for SPP waves to exist for all tilt angles. Also, the SPP wave can be excited in both prism-coupled configurations only by p-polarized plane waves.

Infrared Propagating Electromagnetic Surface Waves Excited by Induction

AbstractPropagating inhomogeneous electromagnetic waves called surface plasmon polaritons (SPPs) can be excited by free-space beams on corrugated conducting surfaces at resonance angles determined by corrugation period, permittivity, and optical frequency. SPPs are coupled to and co-propagate with surface charge displacements. Complete electrical isolation of individual conducting corrugations prevents the charge displacement necessary to sustain an SPP, such that excitation resonances of traveling SPPs are absent. However, SPPs can be excited via electric induction if a smooth conducting surface exists below and nearby the isolated conducting corrugations. The dependence of SPP excitation resonances on that separation is experimentally investigated here at long-wave infrared wavelengths. We find that excitation resonances for traveling SPPs broaden and disappear as the dielectric’s physical thickness is increased beyond ~1% of the free-space wavelength. The resonance line width increases with refractive index and optical thickness of the dielectric.

Surface plasmon enhancement for microsphere-assisted super-resolution imaging of metallodielectric nanostructures

Using a two-dimensional hexagonally close-packed SiO2/Ag nanoshell array coated with or without a dielectric layer as an imaging object, we find that the imaging quality of microsphere-assisted microscopy depends strongly on the optical properties of the metallodielectric sample. When a thin dielectric film is deposited on the top surface of a SiO2/Ag nanoshell array, a periodic enhanced near-field electric field is formed at the interface between the Ag layer and the deposited dielectric layer due to the excitation of surface plasmon polaritons. By increasing the dielectric constant of the coating layer, the enhanced near-field electric field region becomes larger and extends into the region which is closer to the imaging system. When the SiO2/Ag nanoshell array is coated with a SiO layer, the best resolution, the highest magnification, and the longest working distance are obtained. And, a SiO coated nanoshell array with a core size of 180 nm (λ/3, where λ = 540 nm is the central wavelength of illumination) can be resolved.

Asymmetric Excitation of Surface Plasmon Polaritons via Paired Slot Antennas for Angstrom Displacement Sensing.

Optical antennas enable efficient coupling between propagating light and bonding electromagnetic waves like surface plasmon polaritons (SPPs). Under the illumination of inhomogeneous optical fields, propagating SPPs mediated by multimode antennas could be spatially asymmetric and the asymmetry strongly depends on the position of the antennas relative to the illumination field. Here we develop such asymmetric excitation of SPPs through illuminating a pair of slot antennas with the (1,0) mode Hermite-Gaussian beam. The physical scenario of the interaction between the illumination optical field and the paired slot antennas are elaborated by full-wave electromagnetic simulations. We also carry out experiments to monitor the asymmetric SPPs propagation with a back-focal plane imaging technique. By retrieving the asymmetric intensity ratio of the SPP pattern in the back-focal plane image, lateral displacement of the antennas down to angstrom level is demonstrated.

Spoof surface plasmon polaritons excited leaky-wave antenna with continuous scanning range from endfire to forward

A novel leaky-wave antenna (LWA) utilizing spoof surface plasmon polaritons (SSPPs) excitation is proposed with continuous scanning range from endfire to forward. The designed transmission line unit supports two SSPPS modes, of which the 2nd order mode is applied in the design. A novel strategy has been devised to excite the spatial radiation of the –1st order harmonics by arranging periodic counter changed sinusoidal structures on both sides of the SSPPs transmission line. Both full-wave simulation and measurement results show that the proposed LWA presents wide scanning angle from endfire to forward. In the frequency range from 4 GHz to 10 GHz, LWAs achieve scanning from 90° to +20°, covering the entire backward quadrant continuously.

Beating the shot-noise limit with optical fiber quantum sensors for salinity measurement

An ultra-resolution optical salinity quantum sensor depended on the tapered hetero-core structure coated with a gold film (around 50 nm) is proposed and demonstrated in this paper. Single photons which work as an input source are used for exciting surface plasmon polaritons at the interface between the metal and the seawater. We exploit the statistical analysis method to get the transmission spectroscopy and quantify its estimation error. Experiment results show that the detected estimation errors of the proposed quantum sensor are completely in agreement with the quantum theory. Though various external interference and experimental defects exist, the error bars are beyond the standard quantum limit. The salinity sensitivity of this proposed sensor is about 0.02204/‰. The resolution of this proposed sensor is 0.0016‰, which is one order of magnitude higher than that of traditional optical fiber surface plasmon resonance (SPR) sensors. The resolution and the sensitivity of the quantum sensor can be further enhanced by modifying the metal coating and the structural parameters. This work realizes the combination of optical fiber sensing technology and quantum plasmonic technology, which will pave the way for the development of high-resolution and high-sensitivity sensor.

Magnetic field sensor based on magnetoplasmonic crystal

Here we report on designing a magnetic field sensor based on magnetoplasmonic crystal made of noble and ferromagnetic metals deposited on one-dimensional subwavelength grating. The experimental data demonstrate resonant transverse magneto-optical Kerr effect (TMOKE) at a narrow spectral region of 50 nm corresponding to the surface plasmon-polaritons excitation and maximum modulation of the reflected light intensity of 4.5% in a modulating magnetic field with the magnitude of 16 Oe. Dependences of TMOKE on external alternating current (AC) and direct current (DC) magnetic field demonstrate that it is a possibility to use the magnetoplasmonic crystal as a high-sensitive sensing probe. The achieved sensitivity to DC magnetic field is up to 10−6 Oe at local area of 1 mm2.