Planar Surface Plasmon Research Articles

Nonreciprocity of thermal radiation in attenuated total reflection‐mediated optical waveguide

AbstractFano resonance (FR) and the triggered nonreciprocal thermal radiation (NTR) in a Weyl semimetal (WSM)‐ incorporated Kretschmann configuration has been observed and analyzed. Employing the anisotropic permittivity tensor, the electromagnetic responses of the proposed layered structure have been studied, and we illustrate that FR and strong nonreciprocity is attributed to the coupling between the planar waveguide mode and surface plasmon polaritons in WSM. It is shown that absorptivity (α) is not consistent with emissivity (e) in the considered angular range, which confirms near‐complete violation of Kirchhoff's law with nonmagnetic WSM. To analyze the physical origin of NTR, we performed numerical calculations for the α, e, nonreciprocity (η), as well as the magnetic field inside each layer. The compre‐hensive investigation of η with regard to geometric parameters suggests great potential for the practical use of perfect absorption and NTR over a wide range of frequencies and layer thicknesses.

Resonant amplification of slow surface plasmon polaritons in a DC current pumped semiconductor/graphene waveguide with a groove defect

We propose the principle of a planar surface plasmon polariton amplifier composed of a complex waveguide structure based on a semiconductor thin film separated from a dielectric substrate by a graphene monolayer. The amplification of surface plasmon polaritons in that waveguide in the terahertz regime is driven by a direct current in the graphene layer under a synchronism condition that allows an efficient energy exchange from the collective flux of charge carriers in graphene and the surface electromagnetic wave in the semiconductor film. Positive feedback required for resonant amplification is achieved through surface plasmon polariton reflections at the edges of the active waveguide, one of which is formed by a local thickness defect (a groove) at the upper surface of the semiconductor film that also provides an exit channel for the energy of the amplified surface wave to be transferred to an adjacent passive thin film semiconductor waveguide. We determine the conditions required for the resonant amplification of surface plasmon polaritons in that complex structure, which are essentially governed by the geometry of the groove as well as by the characteristic parameters of the active and passive waveguides.

Design and Analysis of Planar Waveguide-Based SPR Sensor for Formalin Detection Using Ag-Chloride-BP Structure.

Nowadays, Food additives and preservatives have become a hot topic especially formalin, which is a chemical substance used to preserve food. Chronic cancer is caused by swallowing the formalin-contaminated food on a regular basis. As a result, detection of the formalin in food ingredients is a critical need, and this requirement is becoming increasingly important in new terrains. Therefore, a new approach, planar waveguide-based surface plasmon resonance (SPR) sensor is presented in this paper employing silver-chloride materials-black phosphorus structure to detect the formalin. In this study, the optimization of metal thickness and optimal performance of chloride material are analyzed by observing the transmittance power and resonance shift for conventional and chloride-based sensors, respectively. Moreover, the performance parameters, such as sensitivity of 344°/RIU, quality-factor of 166.99RIU-1, detection-accuracy of 3.34 and figure-of-merit of 164.74, are observed for the proposed sensor. Furthermore, the performance comparative study is conducted and found that the proposed sensor highlighted the enhanced the SPR sensor and highlighted the performance of FOM. Finally, the electromagnetic filed distributions of the proposed WG-based SPR sensor are shown using the Opti-FDTD software.

Field-Effect Transistor with a Plasmonic Fiber Optic Gate Electrode as a Multivariable Biosensor Device.

A novel multivariable system, combining a transistor with fiber optic-based surface plasmon resonance spectroscopy with the gate electrode simultaneously acting as the fiber optic sensor surface, is reported. The dual-mode sensor allows for discrimination of mass and charge contributions for binding assays on the same sensor surface. Furthermore, we optimize the sensor geometry by investigating the influence of the fiber area to transistor channel area ratio and distance. We show that larger fiber optic tip diameters are favorable for electronic and optical signals and demonstrate the reversibility of plasmon resonance wavelength shifts after electric field application. As a proof of principle, a layer-by-layer assembly of polyelectrolytes is performed to benchmark the system against multivariable sensing platforms with planar surface plasmon resonance configurations. Furthermore, the biosensing performance is assessed using a thrombin binding assay with surface-immobilized aptamers as receptors, allowing for the detection of medically relevant thrombin concentrations.

Patterning of transition metal dichalcogenides catalyzed by surface plasmons with atomic precision

Summary Plasmon-induced charge transfer has drawn considerable interests and spurred rapid developments of photovoltaics and photocatalysis. Various plasmonic metal/transition metal dichalcogenide (TMD) heterostructures have been developed to promote charge separation. For plasmon-induced catalysis, the transformation of TMDs is rare, and the erosion of TMDs has not yet been reported. Here, we report the etching of two-dimensional TMDs by planar surface plasmon polaritons (SPPs). We found that SPPs can etch various TMDs into desired layers and lateral size through controlling the light power and incident direction. In aqueous media, the strong plasmonic coupling at Au/MoS2 interface generates holes in the valence band of MoS2 that can weaken its interlayer interaction. As a synergistic effect, the plasmonic hot electrons produce oxidizing H2O2 to dissolve MoS2 from the top layers. Our results provide a new perspective for understanding the plasmonic coupling at metal-TMD interfaces and a reliable route toward fabricating well-defined TMDs.

Asymmetric dielectric grating on metallic film enabled dual- and narrow-band absorbers.

We investigated a mid-infrared (mid-IR) dual-band absorber consisting of a continuous gold film coated with an asymmetric silicon grating. In each unit cell of the grating, there are three unequally spaced silicon strips. Numerical results reveal that the (+1, -1) planar surface plasmon polariton (SPP) waves excited by the transverse-magnetic (TM) incidence can be coupled with different Fabry-Pérot (FP) resonances and the resonant energy is dissipated to the ohmic loss. Under the normal incidence condition, the absorber provides two high-absorbance peaks at wavelengths of 3.856 µm and 4.29 µm, with the absorption bandwidths of ∼25.7 cm-1 and ∼21.5 cm-1. When changing the angle of the incidence, it is observed an interesting feature that either of the peaks does not split. The presented structure offers an approach to the design of optical components for multi-spectral control of mid-IR signals.

Limits of the Effective Medium Theory in Particle Amplified Surface Plasmon Resonance Spectroscopy Biosensors

The resonant wave modes in monomodal and multimodal planar Surface Plasmon Resonance (SPR) sensors and their response to a bidimensional array of gold nanoparticles (AuNPs) are analyzed both theoretically and experimentally, to investigate the parameters that rule the correct nanoparticle counting in the emerging metal nanoparticle-amplified surface plasmon resonance (PA-SPR) spectroscopy. With numerical simulations based on the Finite Element Method (FEM), we evaluate the error performed in the determination of the surface density of nanoparticles σ when the Maxwell-Garnett effective medium theory is used for fast data processing of the SPR reflectivity curves upon nanoparticle detection. The deviation increases directly with the manifestations of non-negligible scattering cross-section of the single nanoparticle, dipole-dipole interactions between adjacent AuNPs and dipolar interactions with the metal substrate. Near field simulations show clearly the set-up of dipolar interactions when the dielectric thickness is smaller than 10 nm and confirm that the anomalous dispersion usually observed experimentally is due to the failure of the effective medium theories. Using citrate stabilized AuNPs with a nominal diameter of about 15 nm, we demonstrate experimentally that Dielectric Loaded Waveguides (DLWGs) can be used as accurate nanocounters in the range of surface density between 20 and 200 NP/µm2, opening the way to the use of PA-SPR spectroscopy on systems mimicking the physiological cell membranes on SiO2 supports.

Rejection of Spoof SPPs Using the Second Resonant Mode of Vertical Split-Ring Resonator

In this letter, the studies of the vertical split-ring resonator (VSRR) at its second resonant mode are carried out for the first time. The VSRR can be regarded as an electric resonator at such resonant mode, which is proven by its resonant current distribution. Then, a new type of rejection plasmonic filter is constructed by adding the VSRR on the planar spoof surface plasmon polariton (SPP) waveguide using double-side corrugated metallic strips. The second resonance of the VSRR is excited by the $z$ -component of the electric field of the spoof SPP mode, near which the SPP propagation is prevented. Utilizing this principle, a plasmonic filter with broadband rejection is designed and fabricated. The measurement result is presented to confirm the highly efficient filtering performance of the proposed filter, which makes it possible to be applied in the advanced integrated plasmonic devices and circuits at microwave and terahertz frequencies.

Coherence lattices in surface plasmon polariton fields.

We explore electromagnetic coherence lattices in planar polychromatic surface plasmon polariton (SPP) fields. When the SPP constituents are uncorrelated-and thus do not interfere-coherence lattices arise from statistical similarity of the random SPP electromagnetic field. As the SPP correlations become stronger, the coherence lattices fade away, but the lattice structure reemerges in the spectral density of the field. The polarization states of the structured SPP lattice fields are also investigated. Controllable plasmonic coherence and spectral density lattices can find applications in nanophotonics, such as nanoparticle manipulation.

A High-Gain Planar Surface Plasmon Wave Antenna Based on Substrate Integrated Waveguide Technology With Size Reduction

This communication presents a miniaturized printed circuit board (PCB)-based surface plasmon wave antenna with high gain designed using substrate integrated waveguide (SIW) technology. The periodic grooves made on substrate provide constructive superposition of electric field due to surface plasmon resonances which lead to an antenna gain enhancement. Furthermore, using PCB with a high relative permittivity shifts the surface plasmon resonance to lower frequencies and shrinks the antenna size. The antenna is fed from the bottom layer by a feed line which couples the power to patch and surface plasmon waves through a cavity. Then, the power is propagated by the patch and SIW grooves where surface plasmons resonate. The measurement results show that a high gain of 17.4 dBi is achieved along with a narrow beamwidth and a low sidelobe level of 11 dB, approximately.

Ultracompact Pseudowedge Plasmonic Lasers and Laser Arrays.

Concentrating light at the deep subwavelength scale by utilizing plasmonic effects has been reported in various optoelectronic devices with intriguing phenomena and functionality. Plasmonic waveguides with a planar structure exhibit a two-dimensional degree of freedom for the surface plasmon; the degree of freedom can be further reduced by utilizing metallic nanostructures or nanoparticles for surface plasmon resonance. Reduction leads to different lightwave confinement capabilities, which can be utilized to construct plasmonic nanolaser cavities. However, most theoretical and experimental research efforts have focused on planar surface plasmon polariton (SPP) nanolasers. In this study, we combined nanometallic structures intersecting with ZnO nanowires and realized the first laser emission based on pseudowedge SPP waveguides. Relative to current plasmonic nanolasers, the pseudowedge plasmonic lasers reported in our study exhibit extremely small mode volumes, high group indices, high spontaneous emission factors, and high Purell factors beneficial for the strong interaction between light and matter. Furthermore, we demonstrated that compact plasmonic laser arrays can be constructed, which could benefit integrated plasmonic circuits.

Modelling of the effective dielectric constant of planar spoof surface plasmon polariton waveguides

The modelling of the effective dielectric constant of a planar spoof surface plasmon polariton waveguide for X-band frequencies is presented. The waveguide has a single conductor structure that is corrugated on both sides. A methodology to extract the effective dielectric constant of waveguides with complex patterns and a novel closed-form formula based on complex analysis of the structure and empirical methods are suggested. The suggested formula is a function of the corrugation depth, aperture, periodicity, thickness of the substrate material and permittivity. The worst case error between the formula and measurement result is 8.4%, which is much lower than the previously reported coplanar stripline formulation approach having an error of 14.5%.

Radiation loss of planar surface plasmon polaritons transmission lines at microwave frequencies

Radiation loss of a typical spoof surface plasmon polaritons (SSPPs) transmission line (TL) is investigated in this paper. A 325 mm-long SSPPs TL is designed and fabricated. Simulated results show that radiation loss contributes more to transmission loss than dielectric loss and conductor loss from 2 GHz to 10 GHz. Radiation loss of the SSPPs TL could be divided into two parts, one is caused by the input mode converter, and the other is caused by the corrugated metallic strip. This paper explains mechanisms of radiation loss from different parts, designs a loaded SSPPs TL with a series of resistors to absorb electromagnetic energy on corrugated metallic strip, and then discriminates radiation loss from the input mode converter, proposes the concept of average radiation length (ARL) to evaluate radiation loss from SSPPs of finite length, and concludes that radiation loss is mainly caused by corrugated structure of finite length at low frequency band and by the input mode converter at high frequency band. To suppress radiation loss, a mixed slow wave TL based on the combination of coplanar waveguides (CPWs) and SSPPs is presented. The designed structure, sample fabrication and experimental verification are discussed.

Studying the electrochemistry of single nanoparticles with surface plasmon resonance microscopy

Surface plasmon resonance microscopy (SPRM) is an emerging label-free optical microscopic imaging technology. It utilizes the planar surface plasmon resonance effect to visualize the optical mass of individual nano-objects. On the basis of appropriate optical-to-electrochemical conversion models, electrochemical current associated with individual nanoparticles can be quantitatively resolved from SPRM images recorded during electrochemical reactions, allowing for cyclic voltammetry and chronoamperometry analysis at single nanoparticle level. More importantly, the spatial resolution of SPRM further enables us to investigate the structure–activity relationship in a bottom-up manner by correlating the structure (from electron microscopes) and the electrochemical activity (from SPRM) of the very same individuals. In this mini-review, we summarize our recent work on using SPRM to study the electrochemical activities of single nanoparticles, and provide our opinions on the challenges and future research directions in this field.

Frequency-Controlled Broad-Angle Beam Scanning of Patch Array Fed by Spoof Surface Plasmon Polaritons

Frequency-controlled broadband and broad-angle beam scanning is proposed using a circular-patch array fed by planar spoof surface plasmon polaritons (SPPs). Here, a row of circularly metallic patches is placed near an ultrathin planar spoof SPP waveguide. When the SPP wave is transmitted through the waveguide, the circular patches are fed at the same time. Because of the phase difference fed to the patches, the proposed structure can realize wide-angle beam scanning from backward direction to forward direction as the frequency changes, breaking the limit of traditional leaky-wave antennas. Both numerical simulations and measured results demonstrate good performance of the proposed structure. It is shown that the scanning angle can reach 55° with an average gain level of 9.8 dBi. The proposed frequency scanning patch array is of great value in planar integrated communication systems.

Mode structure of planar optical antennas on dielectric substrates.

We report a numerical study, supported by photoemission electron microscopy (PEEM), of sub-micron planar optical antennas on transparent substrate. We find these antennas generate intricate near-field spatial field distributions with odd and even numbers of nodes. We show that the field distributions are primarily superpositions of planar surface plasmon polariton modes confined to the metal/substrate interface. The mode structure provides opportunities for coherent switching and optical control in sub-micron volumes.

Dual-Band Planar Plasmonic Unidirectional Launching in a Semiannular Apertures Array

Multiple-band, frequency-adjustable unidirectional launching of planar surface plasmons is of great concern in plasmonic devices and circuits. We have designed and demonstrated a novel dual-band planar unidirectional surface plasmon polaritons (SPPs) launcher with narrow bandwidth (∼5 nm) and large band gap (∼50 nm) using a semiannular apertures array milled in a gold film. Symmetry breaking of the semiannular aperture brings significant advantages for the unidirectional launching, based on the excited asymmetrically distributed cylindrical surface plasmon resonance modes. During the unidirectional launching, the individual semiannular apertures function as unidirectional quasi-point SPP sources, and the grating coherently stacking amplitude of unidirectional SPPs functions as an amplifier. By controlling the semiannular aperture size, we achieved large range modulations of wavelengths beyond 60 nm for both bands. This efficient unidirectional launching is experimentally demonstrated for 632 nm, showing g...

Surface plasmon wave application in microwave modulator induced by switchable metamaterial

ABSTRACTCorrugated metal surface with underlayer metal ground can propagate surface waves when the operation frequency is below the asymptotic limit–the surface plasma frequency. Tunability of the spoof surface plasmon polariton (SSPP) wave is realized by placing metamaterial underneath the SSPP strip. We design and experimentally demonstrate a modulator based on the planar surface plasmon waveguide and switchable metamaterial, where PIN diodes are implemented to tune the metamaterial. With the diodes working in on/off states, the proposed modulator can be, respectively, viewed as a signal‐stop/signal‐pass circuit at the operation frequency. The experimental results validated this method. It is observed that the proposed modulator would operate from 2.51 to 2.57 GHz with 12 dB on‐off isolation. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:261–263, 2016

Mode size and loss in strongly asymmetric plasmonic waveguide with dielectric cladding

The effect of dielectric cladding on modifying a mode field based on a multilayer planar surface plasmon polariton (SPP) waveguide is investigated at the telecom wavelength of 1.55 μm. Through numerical calculations based on the transfer matrix method and Cauchy integration method, we point out that the mode loss and the mode size can be efficiently engineered via tailoring the dielectric cladding layer. With appropriately optimized thickness and refractive index of the dielectric cladding, the mode size and mode loss of the long-range SPP modes supported by the proposed structure could reach their minima simultaneously such that the figure of merit exhibits a maximum, which breaks the trade-off relationship between confinement and attenuation of SPP waveguide to a certain degree. Furthermore, benefiting from the dielectric cladding effect, the adjustability of field distribution in the dielectric region provides a simple and effective means for improving the light–matter interaction strength for the purpose of SPP signal modulating, detecting or sensing.

Planar spoof plasmonic ultra-wideband filter based on low-loss and compact terahertz waveguide corrugated with dumbbell grooves.

Although subwavelength planar terahertz (THz) plasmonic devices can be implemented based on planar spoof surface plasmons (SPs), they still suffer from a little high propagation loss. Here the dispersion and propagation characteristics of the spoof plasmonic waveguide composed of double metal strips corrugated with dumbbell shaped grooves have been investigated. It has been found that much lower propagation loss and longer propagation length can be achieved based on the waveguide compared with the conventional spoof plasmonic waveguide with rectangular grooves. Moreover, the waveguide can implement a decrease in size of about 22%. An ultra-wideband THz plasmonic filter for planar circuits has been demonstrated based on the proposed waveguide. The experimental verification at the microwave frequency has been conducted by scaling up the geometry size of the filter.