Excitation Of Surface Plasmon Polaritons Research Articles

Surface-Enhanced Raman Scattering and Fluorescence on Gold Nanogratings.

Surface-enhanced Raman scattering (SERS) spectroscopy is a sensitive sensing technique. It is desirable to have an easy method to produce SERS-active substrate with reproducible and robust signals. We propose a simple method to fabricate SERS-active substrates with high structural homogeneity and signal reproducibility using electron beam (E-beam) lithography without the problematic photoresist (PR) lift-off process. The substrate was fabricated by using E-beam to define nanograting patterns on the photoresist and subsequently coat a layer of gold thin film on top of it. Efficient and stable SERS signals were observed on the substrates. In order to investigate the enhancement mechanism, we compared the signals from this substrate with those with photoresist lifted-off, which are essentially discontinuous gold stripes. While both structures showed significant grating-period-dependent fluorescence enhancement, no SERS signal was observed on the photoresist lifted-off gratings. Only transverse magnetic (TM)-polarized excitation exhibited strong enhancement, which revealed its plasmonic attribution. The fluorescence enhancement showed distinct periodic dependence for the two structures, which is due to the different enhancement mechanism. We demonstrate using this substrate for specific protein binding detection. Similar periodicity dependence was observed. Detailed theoretical and experimental studies were performed to investigate the observed phenomena. We conclude that the excitation of surface plasmon polaritons on the continuous gold thin film is essential for the stable and efficient SERS effects.

Excitation of graphene surface plasmons polaritons by guided-mode resonances with high efficiency.

An Otto-like configuration for the excitation of graphene surface plasmon polaritons (GSPPs) is proposed. The configuration is composed of a metallic grating-dielectric-waveguide structure and a monolayer graphene with a subwavelength vacuum gap between them. The evanescent field located at the bottom surface of the dielectric waveguide corresponding to grating-coupled guided-mode resonances (GMRs) is utilized to efficiently excite the highly confined GSPPs. The finite difference time domain method is used to investigate the behaviors of the GMR-GSPP hybrid modes. The dispersion relations of GMRs and GSPPs are calculated and the numerical results further identify the excitation of GMR-GSPP hybrid modes. By changing the gap between the graphene layer and the bottom of the dielectric waveguide and the Fermi energy of graphene, the resonant frequencies of GMR-GSPP hybrid modes can be continuously tuned. When the optimized excitation condition is satisfied, the maximum energy enhancement factor in the gap can reach about 500 at the resonant frequencies. The proposed structure can be used to realize highly sensitive, compatible with planar fabrication technology, and electrically (mechanically) tunable sensors.

Acoustic plasmonics of Au grating/Bi2Se3 thin film/sapphire hybrid structures**Project supported by Carl-Zeiss-Stiftung

The surface plasmon polaritons of the topological insulator Bi2Se3 can be excited by using etched grating or grave structures to compensate the wave vector mismatch of the incident photon and plasmon. Here, we demonstrate novel gold grating/Bi2Se3 thin film/sapphire hybrid structures, which allow the excitation of surface plasmon polaritons propagating through nondestructive Bi2Se3 thin film with the help of gold diffractive gratings. Utilizing periodic Au surface structures, the momentum can be matched and the normal-incidence infrared reflectance spectra exhibit pronounced dips. When the width of the gold grating W (with a periodicity 2W) increases from 400 nm to 1500 nm, the resonant frequencies are tuned from about 7000 cm−1 to 2500 cm−1. In contrast to the expected dispersion for both massive and massless fermions, where q ∼ π/W is the wave vector, we observe a sound-like linear dispersion even at room temperature. This surface plasmon polaritons with linear dispersion are attributed to the unique noninvasive fabrication method and high mobility of topological surface electrons. This novel structure provides a promising application of Dirac plasmonics.

Graphene hybrid waveguide stimulation using a photoconductive terahertz generator.

Typically, terahertz (THz) surface plasmon polariton (SPP) excitation involves phase-matching engineering and THz plane-wave generation. This requires antennas, lenses, and other optical phase-matching devices. Herein, we demonstrate a novel, to the best of our knowledge, method to excite THz SPPs in graphene directly by using an 800 nm optical pump and a photoconductive source. We miniaturize the SPP excitation setup by eliminating the plane-wave generator and the need for mode matching between the plane wave and the waveguide, thereby improving the power efficiency of THz SPP excitation; an average SPP power of 0.6 mW is obtained for an optical pump power of 25 mW.

Plasmonic electro-optic modulator based on degenerate semiconductor interfaces

Abstract We present a semiconductor-based optoelectronic switch based on active modulation of surface plasmon polaritons (SPPs) at lattice-matched indium gallium arsenide (In0.53Ga0.47As) degenerately doped pn++ junctions. The experimental device, which we refer to as a surface plasmon polariton diode (SPPD), is characterized electrically and optically, showing far-field reflectivity modulation for mid-IR wavelengths. Self-consistent electro-optic multiphysics simulations of the device’s electrical and electromagnetic response have been performed to estimate bias-dependent modulation and switching times. The numerical model shows a strong agreement with the experimental results, validating the claim of excitation and modulation of SPPs at the junction, thus potentially providing a new pathway toward fast optoelectronic devices.

Ultra-large local field enhancement effect of isolated thick triangular silver nanoplates on a silicon substrate in the green waveband.

The local field enhancement in plasmonic nanostructures is vital for surface enhanced Raman scattering (SERS). However, it remains a challenge to achieve a large local field enhancement at an illumination wavelength in the green waveband. Here we report on an ultra-large local field enhancement effect of isolated thick triangular silver nanoplates (ITTSNPs) on a silicon substrate at an illumination wavelength in the green waveband. We show that when the thickness of the ITTSNP is larger than a critical thickness depending on the illumination wavelength, a large local field enhancement with an enhancement factor (EF) greater than 350 can be achieved at an illumination wavelength in the green waveband, which is due to the excitation of strong localized surface plasmon polaritons only at three top apexes of the ITTSNP. Furthermore, we experimentally demonstrate that at an excitation wavelength of 514.5 nm, the average SERS EF of the ITTSNPs can exceed ${{10}^{11}}$1011, and the sensitivity for the detection of Rhodamine 6 G molecules can reach ${{10}^{ - 12}}\;{\rm M}$10-12M.

Quantization of graphene plasmons

In this article we perform the quantization of graphene plasmons using both a macroscopic approach based on the classical average electromagnetic energy and a quantum hydrodynamic model, in which graphene charge carriers are modeled as a charged fluid. Both models allow to take into account the dispersion of graphenes optical response, with the hydrodynamic model also allowing for the inclusion of non-local effects. Using both methods, the electromagnetic field mode-functions, and the respective frequencies, are determined for two different graphene structures. we show how to quantize graphene plasmons, considering that graphene is a dispersive medium, and taking into account both local and nonlocal descriptions. It is found that the dispersion of graphene's optical response leads to a non-trivial normalization condition for the mode-functions. The obtained mode-functions are then used to calculate the decay of an emitter, represented by a dipole, via the excitation of graphene surface plasmon-polaritons. The obtained results are compared with the total spontaneous decay rate of the emitter and a near perfect match is found in the relevant spectral range. It is found that non-local effects in graphene's conductivity, become relevant for the emission rate for small Fermi energies and small distances between the dipole and the graphene sheet.

Boundary graphene layer effect on surface plasmon oscillations in a quantum plasma half-space

The effect of graphene on unique features of surface plasmon-polariton excitations near the interface of vacuum and quantum plasma half-space is explored using a quantum hydrodynamic model including the Fermi electron temperature and the quantum Bohm potential together with the full set of Maxwell equations. It is found that graphene as a conductive layer significantly modifies the propagation properties of surface waves by making a change on the corresponding wave dispersion relation. It is shown that the presence of graphene layer on the interface of vacuum and plasma leads to a blue-shift in the surface Plasmon frequency. The results of present study must be contributed to the modern electronic investigations.

Engineering of optical, magneto-optical and magnetic properties of nickel-based one-dimensional magnetoplasmonic crystals

Magnetoplasmonic crystals consisted of the combination of noble and ferromagnetic thin films deposited on diffraction gratings represent a special class of nanostructures that can utilize the magneto-optical Kerr effect enhanced by surface plasmon-polaritons excitation for the probing of an external DC magnetic field. Optical and magneto-optical properties of a magnetoplasmonic crystal are formed by magnetic behavior. This article represents ways to manipulate optical, magneto-optical and magnetic properties of nickel-based magnetoplasmonic crystals by the variation of the substrate parameters, the composition of magnetoplasmonic crystals as well as the compressive mechanical stresses on the surface of a ferromagnetic layer.

Evanescent coupling to silicon waveguides using surface plasmon polaritons.

In this work, we discuss evanescent light coupling to silicon waveguides using surface plasmon polaritons (SPPs) in the Otto configuration. The setup for excitation of SPPs includes a fused-silica prism, a 100nm silver layer with a 650nm airgap between them, and a tapered silicon waveguide located across from the silver layer. A $p$p-polarized light of 1550nm wavelength is incident at plasmonic angle of 44° to the interface of the fused silica-airgap to excite the SPP.A 2D Lumerical FDTD Solutions simulation shows a coupling efficiency of 54%. The fabricated device on a silicon-on-insulator substrate shows 10% light transmission for $p$p-polarized light.

Correction to: Polarization Transformation of Electromagnetic Radiation Upon Excitation of Surface Plasmon-Polaritons on a Metallic Grating

To the article “Polarization Transformation of Electromagnetic Radiation Upon Excitation of Surface Plasmon-Polaritons on a Metallic Grating,” by I. Z. Indutnyi, V. I. Mynko, M. V. Sopinskyy, and K. V. Svezhentsova, Vol. 86, No. 6, pp. 1058–1063, January, 2020.

Geometrically Tunable Beamed Light Emission from a Quantum‐Dot Ensemble Near a Gradient Metasurface

AbstractOptical metasurfaces have been widely investigated in recent years as a means to tailor the wavefronts of externally incident light for passive device applications. At the same time, their use in active optoelectronic devices such as light emitters is far less established. This work explores their ability to control the radiation properties of a nearby continuous ensemble of randomly oriented incoherent dipole sources via near‐field interactions. Specifically, a film of colloidal quantum dots is deposited on a plasmonic metasurface consisting of a 1D array of metallic nanoantennas on a metal film. The array is designed to introduce a linear phase profile upon reflection, and a bi‐periodic nanoparticle arrangement is introduced to ensure adequate sampling of the desired phase gradient. Highly directional radiation patterns are correspondingly obtained from the quantum dots at an enhanced emission rate. The underlying radiation mechanism involves the near‐field excitation of surface plasmon polaritons at the metal film, and their selective diffractive scattering by the metasurface into well‐collimated beams along predetermined geometrically tunable directions. These results underscore the distinctive ability of metasurfaces to control radiation properties directly at the source level, which is technologically significant for the continued miniaturization and large‐scale integration of optoelectronic devices.

Evaluation of surface roughness of metal films using plasmonic Fano resonance in attenuated total reflection

Attenuated total reflection (ATR) by surface plasmon polariton (SPP) is a method for evaluating the dispersion relation of SPP from the position of a dip in the reflection spectrum. However, recent studies have shown that the dips are displaced from SPP resonance because they are produced by a type of Fano resonance, i.e., the interference between the resonant reflection process accompanied by resonant excitation of SPP and the direct reflection process without resonant excitation. This result suggests that the system properties difficult to be achieved in the dispersion relation of SPP can be characterized using the ATR method. In this study, we investigate the effect of surface roughness due to nanosized dimples created in the initial stage of pitting corrosion on the ATR spectrum, from the viewpoint of Fano resonance. Using the temporal coupled-mode method, it is shown that the Fano resonance in ATR is caused by the phase change of direct reflection because of the absorption on the metal surface, and the spectral shape is determined by this phase, along with the ratio of the external (radiative) decay rate to the total decay rate of the resonant mode. Moreover, it is clarified that the internal and external decay rates extracted from the ATR spectrum provide information on corrosion, such as the effective thickness of the metal film and the randomness in dimple distribution.

A Broadband Tunable Terahertz Metamaterial Absorber Based on Single-Layer Complementary Gammadion-Shaped Graphene.

We present a simple design of a broadband tunable metamaterial absorber (MMA) in the terahertz (THz) region, which consists of a single layer complementary gammadion-shaped (CGS) graphene sheet and a polydimethylsiloxane (PDMS) dielectric substrate placed on a continuous metal film. The Fermi energy level (Ef) of the graphene can be modulated dynamically by the applied DC bias voltage, which enables us to electrically control the absorption performance of the proposed MMA flexibly. When Ef = 0.8 eV, the relative bandwidth of the proposed MMA, which represents the frequency region of absorption beyond 90%, can reaches its maximal value of 72.1%. Simulated electric field distributions reveal that the broadband absorption mainly originates from the excitation of surface plasmon polaritons (SPPs) on the CGS graphene sheet. Furthermore, the proposed MMA is polarization-insensitive and has wide angles for both transverse-electric (TE) and transverse-magnetic (TM) waves in the broadband frequency range. The broadband absorption capacity of the designed MMA can be effectively adjusted by varying the Fermi energy level of graphene. Lastly, the absorbance of the MMA can be adjusted from 42% to 99.1% by changing the Ef from 0 eV to 0.8 eV, which is in agreement with the theoretical calculation by using the interference 41theory. Due to its simple structure and flexible tunability, the proposed MMA has potential application prospects in tunable filtering, modulators, sensing, and other multispectral devices.

Epsilon-near-zero response in indium tin oxide thin films: Octave span tuning and IR plasmonics

Epsilon near zero (ENZ) materials exhibit strongly confined optical modes and plasmonic response around and beyond the ENZ wavelength (λENZ). In order to exploit the novel properties of ENZ materials for real-world applications, it is important to develop material platforms that offer continuous tuning of λENZ. We report octave span, controllable, and reversible tuning of λENZ from 1280 nm to 2900 nm in commercially available thin films of indium tin oxide (ITO), employing a low temperature annealing protocol. Electrical, spectroscopic, and optical measurements establish the physical basis of the observed tunability in free electron density by over an order of magnitude and quantify the real and imaginary components of the refractive index for ITO thin films. Excitation of surface plasmon polaritons (SPPs) in the metallic regime of ITO probes its infrared plasmonic response demonstrating continuous tunability of SPP frequency and crossover to the tunable ENZ plasmon mode in ultrathin films. Finally, dispersion tuning of optical fiber modes by optical coupling with a tunable λENZ platform is demonstrated by investigating modal interference in a tapered silica fiber in contact with various custom tuned ITO films.

Surface plasmon based 1D-grating device for efficient sensing using noble metals

This study presents the design and optimization of device with 1D nanostructured grating modeled on gold (Au), silver (Ag) and copper (Cu) for sensing a minor variation in refractive index (RI). This small change in the adjacent media to metallic grating is detected quite effectively using the unique characteristic of the surface plasmon polaritons (SPPs). The electric field (E-field) of the SPPs penetrates into the nearby media which is very sensitive to slight change in RI. The grating devices has been simulated by using COMSOL Multiphysics 5.3a with periodicity 700 nm, film thickness 50 nm and optimum slit width 300 nm in correspondence with fundamental plasmonic mode. The 0th order transmission spectra have been extracted from each grating device by illuminating (through the substrate side) with p-polarized light at normal incidence. The change in RI of analyte studied to have a significant effect on the resonance wavelength. The sensitivity has been calculated as 700, 731 and 722 nm/RIU for Au, Ag and Cu grating devices respectively which is remarkable. The stability and quick sensing of Au-device make it suitable for application besides some other deficiencies (e.g. slightly less sensitivity as compared to Ag) which should be compromised. Near field analysis has been performed to apprehend the underlying physics connected with each resonance. The highest value of electric and magnetic fields (E-field and H-field) are obtained in the case of Au grating indicating the most efficient excitation of SPPs. This confirms the reasoning behind the efficient sensitivity of Au grating device and finds applications in medicine.

Tuning the magnetic properties of permalloy-based magnetoplasmonic crystals for sensor applications

Miniature magnetic sensors based on magnetoplasmonic crystals (MPlCs) exhibit high sensitivity and high spatial resolution, which can be obtained by the excitation of surface plasmon polaritons. A field dependence of surface plasmon polaritons’ enhanced magneto-optical response strongly correlates with magnetic properties of MPlCs that can be tuned by changing spatial parameters, such as the period and height of diffraction gratings and thicknesses of functional layers. This work compares the magnetic properties of MPlCs based on Ni80Fe20 (permalloy) obtained from local (longitudinal magneto-optical Kerr effect) and bulk (vibrating-sample magnetometry) measurements and demonstrates an ability to control sensors’ performance through changing the magnetic properties of the MPlCs. The influence of the substrate’s geometry (planar or sinusoidal and trapezoidal diffraction grating profiles) and the thickness of the surface layer is examined.

Excitation of surface plasmon polaritons in a gold nanoslab on ion-exchanged waveguide technology.

Integrated metaphotonic devices has opened new horizons to control light-guiding properties at nanoscale; particularly interesting is the application of plasmonic nanostructures coupled to dielectric waveguides to reduce the inherent light propagation losses in metallic metamaterials. In this contribution, we show the feasibility of using ion-exchanged glass waveguides (IExWg) as a platform for the efficient excitation of surface plasmon polaritons (SPP). These IExWg provide high coupling efficiency and low butt-coupling with conventional dielectric optical waveguides and fibers, overcoming the hard fabrication tunability of commonly used CMOS-guiding platforms. We present a near-field scanning optical microscopy characterization of the propagation characteristics of SPP supported in a gold nanoslab fabricated on top of an IExWg. We found that the SPP can be only be excited with the fundamental TM photonic mode of the waveguide. Thanks to the low propagation loss, low birefringence, and compatibility with optical fibers, glass waveguide technology is a promising platform for the development of integrated plasmonic devices operating at visible and near infrared wavelengths with potential applications in single molecule emission routing or biosensing devices.

Передача и преобразование электромагнитного излучения фотонно-кристаллическими металлодиэлектрическими системами на основе опалов

An experimental study of the optical properties of two types of metal-dielectric composites based on opal matrices was carried out: 1) layered structures obtained by successive deposition of metal and dielectric films on a monolayer of opal globules, where extraordinary transmission and extraordinary absorption of light were detected due to the excitation of surface plasmon polaritons of various types; 2) "massive" opal samples, which were infilled with metal by electrothermodiffusion, where an asymmetric form of Bragg resonance curves was observed, due to the Fano resonance.

Influence of surface plasmon polaritons on heating of gold

SynopsisWe present a detailed investigation of periodic heating of gold and periodic structures formation on a surface induced by surface plasmon polaritons (SPP) after irradiation with ultrashort laser pulses. Conditions of the SPP excitation and influence of the angle of incidence and wavelength of the laser field on the resulting structured heating are analysed in detail.