Plasmon Polariton Modes Research Articles

Surface plasmon resonance sensor based on U-shaped photonic quasi-crystal fiber.

A high-sensitivity surface plasmon resonance (SPR) sensor is designed and analyzed numerically. The sensor is constructed on the eightfold U-shaped photonic quasi-crystal fiber (PQF) and coated with indium tin oxide (ITO). The coupling between the core mode and surface plasmon polariton mode is enhanced due to shortening of the distance between the core and the ITO layer, so that the PQF-SPR sensor exhibits high refractive index (RI) sensitivity in the near-infrared region. The maximum wavelength sensitivity and the corresponding resolution of this sensor are 42,000 nm/RIU and 2.38×10-6RIU, respectively. The average wavelength sensitivity is 12,750 nm/RIU in the refractive index range of 1.306-1.386. This advanced sensor is suitable for the determination of RIs in the near-infrared region.

Interaction of two-dimensional atomic lattices with a single surface plasmon polariton

We study the polaritonic bandstructure of a two-dimensional (2D) atomic lattice coupled to a surface plasmon polariton mode in the single excitation regime. We adopt a Dirichlet-to-Neumann map based computational technique which can accurately model non-Markovian dynamics as well as narrow-bandwidth features associated with any periodic atom-photon system in general. Using this technique, we design a 2D atomic lattice using only two-level atoms, which has an isolated flat polaritonic band where the magnitude of the group velocity for the modes in the band approach zero across the whole Brillouin zone. Such a system could be employed to slow, store, and manipulate single photons in a 2D geometry.

Twist-induced control of near-field heat radiation between magnetic Weyl semimetals

Due to the large anomalous Hall effect, magnetic Weyl semimetals can support nonreciprocal surface plasmon polariton modes in the absence of an external magnetic field. This implies that magnetic Weyl semimetals can find novel application in (thermal) photonics. In this work, we consider the near-field radiative heat transfer between two magnetic Weyl semimetal slabs and show that the heat transfer can be controlled with a relative rotation of the parallel slabs. Thanks to the intrinsic nonreciprocity of the surface modes, this so-called twisting method does not require surface structuring like periodic gratings. The twist-induced control of heat transfer is due to the mismatch of the surface modes from the two slabs with a relative rotation.

Anticrossing Behavior in Nanolayered Heterostructures Caused by Coupling between a Planar Waveguide Mode in an Anthracene Single Crystal and a Silver Surface Plasmon Polariton Mode: Implications for Attenuated Total Reflection Spectroscopy

Coupling between a planar waveguide (PWG) mode in an organic single crystal and a surface plasmon polariton (SPP) mode is investigated in this paper. Anticrossing behavior appearing under the stron...

Conditions for photonic bandgaps in two-dimensional materials

Conditions that define the spectral location of bandgaps in the quasi-transverse magnetic surface plasmon polariton modal dispersion for 2D/quasi-2D materials with a tensor response function, embedded in a simple isotropic medium, are obtained. In the isotropic case, transverse magnetic surface plasmon polariton modes propagate if the surface conductivity is inductive. However, in the anisotropic case considered here, we find that quasi-transverse magnetic modes are supported by surfaces with an inductive effective conductivity seen by the wave along the direction of propagation (written as a weighted sum of the diagonal elements). Examples of natural anisotropic 2D/quasi-2D materials are presented to demonstrate the effectiveness of the method.

Utilization of Trapped Optical Modes for White Perovskite Light-Emitting Diodes with Efficiency over 12%

<h2>Summary</h2> The inferior light extraction efficiency (LEE), which is generally less than 20%, based on optical modeling, and the difficulty in achieving white emission are the two main challenges in the metal-halide-perovskite light-emitting diode (PeLED) field. Herein, we report a simple and efficient approach to construct high-performance white PeLEDs with much-enhanced LEE by coupling a blue PeLED with a layer of red perovskite nanocrystal (PeNC) down-converter through a rationally designed multilayer semitransparent electrode (LiF/Al/Ag/LiF). The red PeNC layer allows the extraction of the trapped waveguide mode and surface plasmon polariton mode in a blue PeLED and converts them to red emission, resulting in over 50% LEE improvement. Simultaneously, the complementary emission spectrum of blue photons and down-converting red photons contributes to a white PeLED with a high external quantum efficiency and luminance of more than 12% and approximately 2,000 cd m⁻², respectively, which represent state-of-the-art results in this field.

Few-layer metamaterials for a spontaneous emission enhancement.

Multilayer hyperbolic metamaterials consisting of alternating metal and dielectric layers have important applications in spontaneous emission enhancement. In contrast to the conventional choice of at least dozens of layers in multilayer structures to achieve tunable Purcell effect on quantum emitters, our numerical calculations reveal that multilayers with fewer layers and thinner layers would outperform in the Purcell effect. These discoveries are attributed to the negative contributions by an increasing layer number to the imaginary part of the reflection coefficient and the stronger coupling between surface plasmon polariton modes on a thinner metal layer. This work could provide fundamental insights and a practical guide for optimizing the local density of optical states enhancement functionality of layered metamaterials.

Surface Plasmon Resonance Sensor Based on Side-Polished D-Shaped Photonic Crystal Fiber With Split Cladding Air Holes

We present and numerically characterize a side-polished D-shaped photonic crystal fiber (PCF) sensor based on plasmon. The coupling properties and sensing performance are investigated through the parameter study of metal thickness and polishing depth by the finite element method. With uniform metal evaporation, the metal–dielectric interfaces of the polished flat plane and inner surfaces of split first-cladding air holes can support two different kinds of surface plasmon polariton (SPP) modes. Each mode has its certain resonance wavelength, which is independent of polishing depth and side-polishing angle, and the resonance intensity of the two modes can be changed by polishing depth and the angle, respectively. In the process of measuring analytes with different refractive indexs (RIs), a two-axis detecting method has been presented to improve the sensitivity. The commercial PCF ESM-12 is used to fabricate the sensor probe with wheel-polishing system, and the experimentally detected data have a good agreement with theoretical simulation. As RI varies, both the resonance and intensity perform linear response with the sensitivity of $2.3319\times 10^{3}$ nm/RIU and –252.86%/RIU, respectively. By detecting the wavelength and intensity at the resonance, the two-axis method has obtained a sensitivity of 127.0902 CI/0.01RIU, which is 9% higher than the conventional method (116.595 CI/0.01RIU) that only measures wavelength shift. This study facilitates a new way for the analysis of D-shaped PCF sensor characteristics and provides a novel detecting method to improve the sensitivity of side-polished SPR sensor.

Linear and Nonlinear Phenomena in a Flow of Surface Plasmon–Polaritons

The excitation and propagation of plasmon–polariton modes are considered at a single interface of a dielectric medium and metal in linear and nonlinear regimes. Physical mechanisms of the emergence of a nonlinear response of free electrons in the metal based on the quantum hydrodynamic model are described. It is shown that the period and profile of the envelope of a cnoidal wave of surface plasmon–polaritons in the nonlinear regime change, depending on the conditions of excitation and the energy density of the exciting electromagnetic wave.

Opto-electromagnetic Responses of Tamm Plasmon Polariton Modes in a Symbiotic Dual-Metallic architecture

We report a Tamm plasmon polariton (TPP) arrangement whose design consists of a thin Silver (Ag) film which is the plasmon-active metal and lies adjacent to the distributed Bragg Reflector (DBR) structure. The DBR consists of periodically stratified layers of Ta2O5 and SiO2. TPP modes are excited through normal incidence using a white light source and we have obtained the corresponding reflectivity spectrum as a function of wavelength. The excitation spectrum is characterized by a sharp and distinguishable reflectivity dip within the photonic band-gap of DBR. Extending this version of the idea, we have replaced the single plasmon-active metal by two metals to overrule the drawbacks of these single metals concerning their physiochemical properties like propagation length, chemical stability, and various losses during propagation of the plasmon wave, etc. Hence, we have obtained the reflectivity characteristics for different bimetallic architecture supporting TPP resonances. Thereafter, we have also obtained the Full Width at Half Minimum (FWHM) wavelengths and Quality Factor (Q-Factor) characteristics as a function of metal thickness for two different plasmon active metallic combinations, where the total bimetallic thickness remains constant. The shortcomings of a particular metal are nullified by the presence of the other metal with it. Such an arrangement is envisioned for the fabrication of nanoscale smart devices like optical and biosensors having potential applications in social welfare domain like monitoring the levels of food adulteration and food safety, etc.

A compact design for narrowband optical absorber based on surface plasmon polaritons

A compact design for realizing narrowband optical absorbers at deep subwavelength is proposed, the physical regime of which is based on the excitation of quasi-surface plasmon polariton (quasi-SPP) mode at metal–substrate interface. Due to its small intrinsic loss balanced with the radiation loss, peak absorbance exceeding 99.9% with full width at half-maximum (FWHM) 2.6 nm is achieved at normal incidence. The spatially resolved feature at fixed wavelength, with narrower angular width and high peak absorbance at larger angle of incidence for TE polarization, makes the design more suitable for potential applications in optical filters, optical measurement, biosensors, and thermal emitters.

Effect of buffer layer index on short range surface plasmon polariton based TE pass polarizer

We investigate theoretically the dependence of the extinction ratio, metal layer thickness and buffer thickness of a short length plasmonic polarizer on the buffer layer index. The polarizer section consists of a thin metal layer above the single mode dielectric waveguide separated by a low index dielectric buffer layer. Strong coupling between the surface plasmon polariton (SPP) mode and the guided mode takes place when their phase constants are matched. The SPP mode being of TM type, interacts with the guided TM mode and is completely absorbed by metal film due to resonant coupling between the two modes. The TE guided mode does not couple to the SPP mode and is passed un-attenuated through the polarizer. The buffer layer thickness can be optimized to maximize the TM mode attenuation and reduce the TE losses, which provides a large extinction ratio. Since the polarizer is based on the interference of the SPP mode and the waveguide mode, a periodic coupling of the field takes place between these two modes. It is shown that for properly optimized layer thicknesses, an extinction ratio exceeding 200 dB can be achieved for various buffer layer indices. Effect of buffer layer index on the polarizer length is also presented.

Extreme local field enhancement by hybrid epsilon-near-zero-plasmon mode in thin films of transparent conductive oxides.

Epsilon-near-zero (ENZ) materials display unique properties, and among them, large local field enhancement at ENZ frequency is of particular interest for many potential applications. In this Letter, we introduce the concept that a combination of epsilon-near-zero and surface plasmon polariton modes can be excited over an interface between a dielectric and a single ENZ layer in a specific frequency region, which can lead to extreme enhancement of local electric field. We demonstrate it with a systematic numerical simulation using finite element analysis and consider two configurations (Kretschmann configuration and a grating configuration), where an indium tin oxide (ITO) layer is sandwiched between two dielectric slabs. We confirm the formation of a hybrid mode at the ITO-dielectric interface at the wavelength of ENZ, as the ITO layer thickness reduces. The hybrid mode provides both high confinement and long propagation distance, which makes it more attractive for many applications than just a pure ENZ mode.

Refractive Index Sensor Based on Metal-Clad Planar Polymer Waveguide Operating at 850 nm

A metal-clad planar polymer waveguide refractive index sensor based on epoxy (EPO) polymer materials by using light intensity interrogation at 850 nm is designed. The polymethyl methacrylate (PMMA) material is deployed as the low refractive index (RI) buffer layer in order to better couple the optical guided mode and the surface plasmon polaritons (SPP) mode for working in water environment. The effects of the gold film thickness, PMMA buffer layer thickness, waveguide layer thickness, waveguide width, and gold length on the sensor sensing characteristics have been comprehensively studied. Simulation results demonstrate that the normalized transmission increases quasi-linearly with the increment of RI of the analyte from 1.33 to 1.46. The sensitivity is 491.5 dB/RIU, corresponding to a high RI resolution of 2.6×10−9 RIU. The designed SPP-based optical waveguide sensor is low-cost, wide-range, and high-precision, and has a broad application prospect in biochemical sensing with merits of miniaturization, flexibility, and multiplexing.

Fast and accurate optical determination of gold-nanofilms thickness

We propose and investigate an alternative optical method to determine the thickness of metallic nanofilms thinner than about 50 nm deposited on glass substrates. The method consists of measuring the internal TM reflectivity as a function of the angle of incidence and fitting the curve with Fresnel formulae for a bilayer system to find the film thickness. Gold nanofilms were fabricated by electron beam evaporation (nominal thicknesses of 20 nm, 30 nm and 50 nm) and characterized by common methods (SEM, AFM, Profilometer). The reflectivity curve of TM (or p) polarized light presents a clear peak around the critical angle with air and then a dip due to the excitation of a surface plasmon-polariton mode at the gold/air interface. Fitting the theoretical model around the reflectivity peak readily gives the film’s thickness, and fitting other sections of the curve away from the critical angle with air without altering the fit around the peak, provides the thickness and effective refractive index of the adhesive layer (Cr, Ti). The present approach to gold nanofilm’s thickness measurement is robust and expeditious. It is less sensitive to surface roughness, contamination and nanofabrication defects such as nanometer sized holes.

Hybrid Tamm-surface plasmon polariton mode for highly sensitive detection of protein interactions.

The total internal reflection ellipsometry (TIRE) method was used for the excitation and study of the sensitivity properties of the hybrid Tamm plasmon polariton - surface plasmon polariton (TPP-SPP) and single surface plasmon resonance (SPR) modes of the GCSF receptor immobilization. Additionally, the optimized sensitivity of the hybrid TPP-SPP mode was investigated and compared with the single SPR mode when the BSA proteins formed a layer on the gold surface. The dispersion relations for the hybrid TPP-SPP and single SPR modes were used to explain the enhanced sensitivity of the ellipsometric parameters for the hybrid TPP-SPP mode over the conventional SPR. The SPP component (δΔh-SPP/δλ=53.9°/nm) of the hybrid TPP-SPP mode was about 6.4 times more sensitive than single SPR (δΔSPR/δλ=8.4°/nm) for the BSA protein layer on the gold film. It was found that the sensitivity of the hybrid plasmonic mode can be made controllable by using the strong coupling effect between the TPP and SPP components. The strong coupling regime reduces absorption and scattering losses of the metal for the SPP component in the hybrid TPP-SPP mode and, as a result, narrows the plasmonic resonance.

Establishing the nonlinear coefficient for extremely lossy waveguides.

The nonlinear coefficient γ is central to the study of cubically nonlinear optical guided-wave structures. It is well understood for lossless waveguides, but less so for lossy systems. A number of methods for calculating γ in lossy systems have been proposed, each resulting in different expressions. Here we identify the most accurate and practical expression for γ. We do so by applying the different expressions γ to air-gold surface plasmon polariton modes in the interband region of gold and compare with a fully numerical iterative method. We thus resolve the outstanding issue of which expression for the nonlinear coefficient to use for lossy waveguides, enabling new insights into the nonlinear response of such systems.

Electron energy loss of ultraviolet plasmonic modes in aluminum nanodisks.

We theoretically investigated electron energy loss spectroscopy (EELS) of ultraviolet surface plasmon modes in aluminum nanodisks. Using full-wave Maxell electromagnetic simulations, we studied the impact of the diameter on the resonant modes of the nanodisks. We found that the mode behavior can be separately classified for two distinct cases: (1) flat nanodisks where the diameter is much larger than the thickness and (2) thick nanodisks where the diameter is comparable to the thickness. While the multipolar edge modes and breathing modes of flat nanostructures have previously been interpreted using intuitive, analytical models based on surface plasmon polariton (SPP) modes of a thin-film stack, it has been found that the true dispersion relation of the multipolar edge modes deviates significantly from the SPP dispersion relation. Here, we developed a modified intuitive model that uses effective wavelength theory to accurately model this dispersion relation with significantly less computational overhead compared to full-wave Maxwell electromagnetic simulations. However, for the case of thick nanodisks, this effective wavelength theory breaks down, and such intuitive models are no longer viable. We found that this is because some modes of the thick nanodisks carry a polar (i.e., out of the substrate plane or along the electron beam direction) dependence and cannot be simply categorized as radial breathing modes or angular (azimuthal) multipolar edge modes. This polar dependence leads to radiative losses, motivating the use of simultaneous EELS and cathodoluminescence measurements when experimentally investigating the complex mode behavior of thick nanostructures.

Scattering of a single plasmon polariton by multiple atoms for in-plane control of light

AbstractWe study the interaction of a single photon in a surface plasmon polariton mode with multiple atoms. We propose a system of two atoms to achieve a tunable scattering from subscattering to superscattering regimes by changing the angle of the incident photon. We also demonstrate a perfect electromagnetically-induced transparency using two atoms with two-level structures. The proposed framework is efficiently scalable to a system with a large number of atoms and opens up the possibility of designing novel atom-based optical devices. We design an atomically thin parabolic mirror to focus single photons and form a quantum mirage in a cavity built from atoms.

Au-ITO deposited D-shaped photonic crystal fiber polarizer with a micro-opening based on surface plasmon resonance

Most of the surface plasmon resonance (SPR) based photonic crystal fiber (PCF) polarization filters have been designed with gold film/wire despite the adhesion of gold to silica is uncertain. In this paper, we use a thin layer of indium-tin-oxide (ITO) in between the polished plane of the D-shaped PCF and gold (Au) film, which assists in adhering. By optimizing the designed parameter, the coupling between the surface plasmon polariton (SPP) mode and core mode is attained at 1.55 μm operating wavelength that ensures the filtering ability of the proposed fiber at C-band optical communication window. The performance characteristics of the filter are analyzed by full-vector finite element method (FEM). Numerical results reveal that the inclusion of ITO layer enhances the filtering performance by increasing the attenuation loss of the undesired polarization mode. In addition, owing to the sharp loss peak response, the full width half maximum (FWHM) is achieved of only 30 nm. Such small FWHM makes the proposed fiber promising as a perfect polarization filter at 1.55 μm. Moreover, we reported extinction ratio as high as 806.52 dB and maximum insertion loss only 0.33 dB. Such appealing performance makes this filter widely applicable in communication networks and integrated optical devices especially in the C-band optical communication window.