Single molecule detection provides detailed information about molecular structures and functions, but it generally requires the presence of a fluorescent marker which can interfere with the activity of the target molecule or complicate the sample production. Detecting a single protein with its natural UV autofluorescence is an attractive approach to avoid all the issues related to fluorescence labelling. However, the UV autofluorescence signal from a single protein is generally extremely weak. Here, we use aluminum plasmonics to enhance the tryptophan autofluorescence emission of single proteins in the UV range. Zero-mode waveguides nanoapertures enable observing the UV fluorescence of single label-free beta-galactosidase proteins with increased brightness, microsecond transit times and operation at micromolar concentrations. We demonstrate quantitative measurements of the local concentration, diffusion coefficient and hydrodynamic radius of the label-free protein over a broad range of zero-mode waveguide diameters. While the plasmonic fluorescence enhancement has generated a tremendous interest in the visible and near-infrared parts of the spectrum, this work pushes further the limits of plasmonic-enhanced single molecule detection into the UV range and constitutes a major step forward in our ability to interrogate single proteins in their native state at physiological concentrations.
The paper proposes a method to characterize the bend discontinuity for plasmonic and spoof plasmonic waveguides in terms of scattering parameters. By means of this method, the waveguide is modelled by a two-port network and its scattering parameters are extracted. The parameters for the L-shaped sharp curved bends at different frequencies and under different bending angles are determined.
A type of Tamm states inside metal-insulator-metal (MIM) waveguides is proposed. An impedance based transfer matrix method is adopted to study and optimize it. With the participation of the plasmonic Tamm states, fields could be enhanced twice: the ffirst is due to the coupling between a normal waveguide and a nanoscaled plasmonic waveguide and the second is due to the strong localization and field enhancement of Tamm states. As shown in our 2D coupling configuration, |E|^2 is enhanced up to 1050 times when 1550 nm light is coupled from an 300 nm Si slab waveguide into an 40 nm MIM waveguide.
A novel type of a plasmonic waveguide has been proposed featuring an "open" design that is easy to manufacture, simple to excite and that offers a convenient access to a plasmonic mode. Optical properties of photonic bandgap (PBG) plasmonic waveguides are investigated experimentally by leakage radiation microscopy and numerically using the finite element method confirming photonic bandgap guidance in a broad spectral range. Propagation and localization characteristics of a PBG plasmonic waveguide have been discussed as a function of the wavelength of operation, waveguide core size and the numb…
Strongly anisotropic media with hyperbolic dispersion can be used for claddings of plasmonic waveguides. In order to analyze the fundamental properties of such waveguides, we analytically study 1D waveguides arranged of a hyperbolic metamaterial (HMM) in a HMM-Insulator-HMM (HIH) structure. We show that hyperbolic metamaterial claddings give flexibility in designing the properties of HIH waveguides. Our comparative study on 1D plasmonic waveguides reveals that HIH-type waveguides can have a higher performance than MIM or IMI waveguides.
Using the ultraviolet autofluorescence of tryptophan aminoacids offers fascinating perspectives to study single proteins without the drawbacks of fluorescence labelling. However, the low autofluorescence signals have so far limited the UV detection to large proteins containing several tens of tryptophan residues. This limit is not compatible with the vast majority of proteins which contain only a few tryptophans. Here we push the sensitivity of label-free ultraviolet fluorescence correlation spectroscopy (UV-FCS) down to the single tryptophan level. Our results show how the combination of nano…
The phenomenon of a dispersion bandgap opening between low-loss spectral windows of odd and even plasmonic modes in a layered insulator-metal-insulator plasmonic waveguide is introduced. Beginning with a three layer plasmonic dispersion relation, we explain and numerically confirm the existence of the plasmonic bandgap, and investigate its properties at a very broad spectrum range from ultraviolet to far infrared. The nature of the observed bandgap opening is explained in terms of the near-zero value of an effective permittivity for plasmonic modes in the waveguide. The adjustment of the plasm…
Large research articles based on graphene have been published in various areas since 2007 due to its unique properties. Among these designed structures, graphene-based plasmonic waveguides are one of the interesting subjects in communications. In this paper, a historical review of plasmonic graphene waveguides is presented. The graphene-based waveguides can be divided into two main categories 1- rectangular and 2- cylindrical waveguides. In both categories, graphene can be only electrically biased or magnetically and electrically biased simultaneously where the conductivity of graphene becomes…
We investigate a short (~1.5μm) partially-corrugated tapered waveguide structure for mode coupling from a silicon micro-slab to a plasmonic nano-gap waveguide at the optical communication frequency. More than 80% transmission efficiency is reported numerically for the first time. The result indicates that the corrugated waveguide structure should not only be helpful for realizing full on-chip silicon plasmonic devices but also a good choice for mode coupling enhancement from dielectric waveguides to plasmonic waveguides. Meanwhile, we point out that the coupling mechanism reported here is diff…
Engineering plasmonic metamaterials with anisotropic optical dispersion enables us to tailor the properties of metamaterial-based waveguides. We investigate plasmonic waveguides with dielectric cores and multilayer metal-dielectric claddings with hyperbolic dispersion. Without using any homogenization, we calculate the resonant eigenmodes of the finite-width cladding layers, and find agreement with the resonant features in the dispersion of the cladded waveguides. We show that at the resonant widths, the propagating modes of the waveguides are coupled to the cladding eigenmodes and hence, are …
By viewing plasmon waves in metallic waveguides as propagating electric and magnetic dipoles we show that according to laws of quantum mechanics they will acquire additional phase when propagating through space with static magnetic field. The new effect is physically different from conventional magneto-plasmonic phenomena and is sufficiently strong to observe it under routinely accessible experimental conditions.
While long-range propagating plasmons have been extensively investigated for implementing on-chip optical sensing platforms, waveguide-excited localized surface plasmon resonance (LSPR) based sensing systems have not yet received much attention. Waveguide excitation and readout as an alternative to free-space light based single-particle spectroscopy are particularly attractive for high-throughput sensing and on-chip drug discovery platforms. Here we present a numerical investigation of the optical response of a waveguide-excited plasmonic dolmen-shaped compound nanoantenna that exhibits a Fano…
Surface plasmon polaritons enable light concentration within subwavelength regions, opening thereby new avenues for miniaturizing the device and strengthening light-matter interactions. Here we realize effective electro-optic modulation in low-loss plasmonic waveguides with the aid of graphene, and the devices are fully integrated in the silicon-on-insulator platform. By advantageously exploiting low-loss plasmonic slot-waveguide modes, which weakly leak into a substrate while feature strong fields within the two-layer-graphene covered slots in metal, we successfully achieve a tunability of 0.…
When a linear chain of plasmonic nano-particles is subject to longitudinal magnetic field, it exhibits optical Faraday rotation. If the magnetized nano-particles are plasmonic ellipsoids arranged as a spiral chain, the interplay between the Faraday rotation and the geometrical spiral rotation (structural chirality) can strongly enhance non-reciprocity. This interplay forms a waveguide that permits one way propagation only, within four disjoint frequency bands; two bands for each direction.
Among various plasmonic waveguides, the metal-insulator-metal (MIM) type is the most promising for true subwavelength photonic integration. To date, many photonic devices based on MIM waveguides have been investigated, including resonators. However, most of the reported MIM ring resonators suffer from low extinction ratios. In this paper, we present a comprehensive analysis of the intrinsic reasons for the low performance of MIM ring resonators, and give the analytical transmission relation for a universal all-pass ring resonator which has coupling loss. Based on the analysis we propose the pl…
A waveguide structure consisting of a tapered nanofiber on a metal film is proposed and analyzed to support highly localized hybrid plasmonic modes. The hybrid plasmonic mode can be efficiently excited through the in-line tapered fiber based on adiabatic conversion and collected by the same fiber, which is very convenient in the experiment. Due to the ultrasmall mode area of plasmonic mode, the local electromagnetic field is greatly enhanced in this movable waveguide, which is potential for enhanced coherence light emitter interactions, such as waveguide quantum electrodynamics, single emitter…
We investigate the quantum entanglement between two quantum dots in a plasmonic waveguide with near-zero mode index, considering the dependence of concurrence on interdot distance, quantum dot-waveguide frequency detuning and coupling strength ratio. High concurrence is achieved for a wide range of interdot distance due to the near-zero mode index, which largely relaxes the strict requirement of interdot distance in conventional dielectric waveguides or metal nanowires. The proposed quantum dot-waveguide system with near-zero phase variation along the waveguide near the mode cutoff frequency s…
Plasmonic waveguides offer the unique possibility to confine light far below the diffraction limit. Past room temperature experiments of single quantum emitters coupled to such waveguides have mainly focused on efficient channelling of the spontaneous emission into waveguide modes after a linear optical excitation. However, only the simultaneous interaction of the emitter with multiple plasmonic fields would lead to functionality in a plasmonic circuit. Here, we demonstrate the nonlinear optical interaction of a single molecule and propagating plasmons. An individual terrylene diimide (TDI) mo…
We analytically and numerically investigate magneto-plasmons in metal films surrounded by a ferromagnetic dielectric. In such waveguide using a metal film with a thickness exceeding the Skin depth, an external magnetic field in the transverse direction can induce a significant spatial asymmetry of mode distribution. Superposition of the odd and the even asymmetric modes over a distance leads to a concentration of the energy on one interface which is switched to the other interface by the magnetic field reversal. The requested magnitude of magnetization is exponentially reduced with the increas…
We investigate the feasibility of CMOS-compatible optical structures to develop novel integrated spectroscopy systems. We show that local field enhancement is achievable utilizing dimers of plasmonic nanospheres that can be assembled from colloidal solutions on top of a CMOS-compatible optical waveguide. The resonant dimer nanoantennas are excited by modes guided in the integrated silicon nitride waveguide. Simulations show that 100 fold electric field enhancement builds up in the dimer gap as compared to the waveguide evanescent field amplitude at the same location. We investigate how the fie…
We propose and theoretically verify an efficient mechanism of broadband coupling between incident light and on-chip dielectric slot waveguide by employing a tapered plasmonic nanoantenna. Nanoantenna receives free space radiation and couples it to a dielectric slot waveguide with the efficiency of up to 20% in a broad spectral range, having a small footprint as compared with the currently used narrowband dielectric grating couplers. We argue that the frequency selective properties of such nanoantennas also allow for using them as ultrasmall on-chip multiplexer/demultiplexer devices.
We theoretically explore the possibility of reducing the propagation loss in a metal-insulator-metal (MIM) waveguide, using mode combinations to achieve wall-avoiding field distributions along a certain propagation length. We present analytical results for several waveguides showing notable loss reduction, and we discuss the tradeoffs between low loss and high confinement present in this technique.
Plasmonic waveguides provide an integrated platform to develop efficient nanoscale ultrafast photonic devices. Theoretical models that describe nonlinear optical phenomena in plasmonic waveguides, usually, only incorporate bulk nonlinearities, while nonlinearities that arise from metallic constituents remained unexplored. In this work, we present a method that enables a generalized treatment of the nonlinearities present in plasmonic waveguides and use it to calculate second-harmonic generation from free electrons through a hydrodynamic nonlocal description. As a general application of our met…
We demonstrate the use of amplitude- and phase-resolved near-field mapping for direct characterization of plasmonic slot waveguide mode propagation and excitation with nanocouplers in the telecom wavelength range. We measure mode's propagation length, effective index and field distribution and directly evaluate the relative coupling efficiencies for various couplers configurations. We report 26- and 15-fold improvements in the coupling efficiency with two serially connected dipole and modified bow-tie antennas, respectively, as compared to that of the short-circuited waveguide termination.
We theoretically investigated the transmission properties of a single plasmon interacting with two-level quantum dots (QDs) and a V-type three-level QD, coupled to plasmonic waveguide, respectively. We investigated the transmission of a single plasmon by a system including a V-type three-level QD and compared it with that by a system including only two-level QDs.
We theoretically investigate several types of plasmonic slot waveguides for enhancing the measured signal in Raman spectroscopy, which is a consequence of electric field and Purcell factor enhancements, as well as an increase in light-matter interaction volume and the Raman signal collection efficiency. An intuitive methodology is presented for calculating the accumulated Raman enhancement factor of an ensemble of molecules in waveguide sensing, which exploits an analytical photon Green function expansion in terms of the waveguide normal modes, and we combine this with a quantum optics formali…
We identify a route towards achieving a negative index of refraction at optical frequencies based on coupling between plasmonic waveguides that support backwards waves. We show how modal symmetry can be exploited in metal-dielectric waveguide pairs to achieve negative refraction of both phase and energy. By properly controlling coupling between adjacent waveguides, a metamaterial consisting of a one-dimensional multilayer stack exhibiting an isotropic index of -1 can be achieved at a free-space wavelength of 400 nm. The general concepts developed here may inspire new low-loss metamaterial desi…
An electromagnetic surface wave carrying orbital angular momentum (AM) is called plasmonic vortex that also carries spin AM originating from evanescent field. In this study, spin and orbital AM of plasmonic vortex in a terahertz cylindrical corrugated waveguide (CCW) are analyzed. We report the extrinsic spin AM of the plasmonic vortex for the first time. The extrinsic spin AM is produced by the rotation of the polarization of the plasmonic vortex whose rotation axis is positioned at the vicinity of the CCW wall. The extrinsic spin AM depends on the intrinsic orbital AM and radius of CCW. The …
We demonstrate a plasmonic route to control the collective spontaneous emission of two-level quantum emitters. Superradiance and subradiance effects are observed over distances comparable to the operating wavelength inside plasmonic nanochannels. These plasmonic waveguides can provide an effective epsilon-near-zero operation in their cut-off frequency and Fabry-Perot resonances at higher frequencies. The related plasmonic resonant modes are found to efficiently enhance the constructive (superradiance) or destructive (subradiance) interference between different quantum emitters located inside t…
In this paper, we design a dielectric-to-plasmonic slot waveguide mode converter based on the hybrid silicon-gold taper. The effects of mode matching, the effective index matching, and the metallic absorption loss on the conversion efficiency are studied. Consequently, a metallic taper-funnel coupler with an overall length of 1.7um is designed to achieve a very high conversion efficiency of 93.3% at 1550 nm. The configuration limitations for not allowing this mode converter to achieve a 100% conversion efficiency are also investigated. Such a high-efficiency converter can provide practical rou…
For integrated optical devices, realistic utilization of the superior wave-matter interaction offered by plasmonics is typically impeded by optical losses, which increase rapidly with mode volume reduction. Although coupled-mode plasmonic structures has demonstrated effective alleviation of the loss-confinement trade-off, stringent symmetry requirements must be enforced for such reduction to prevail. In this work, we report an asymmetric plasmonic waveguide that is not only capable of guiding subwavelength optical mode with long-range propagation, but is also unrestricted by structural, materi…
Evanescently coupled waveguides are a powerful platform to study and visualize the wave dynamics in tight-binding systems. Here, we investigate the propagation of surface plasmon polaritons in arrays of dielectric loaded surface plasmon polariton waveguides with a propagation constant gradient acting as an effective external potential. Using leakage radiation microscopy, we observe in real-space for single site excitation a periodic breathing of the wavepacket and an oscillatory motion in the case of Gaussian excitation of multiple waveguides. The corresponding momentum resolved spectra are co…
We demonstrate a way to coherently control light at the nanoscale and achieve coherent perfect absorption (CPA) by using epsilon-near-zero (ENZ) plasmonic waveguides. The presented waveguides support an effective ENZ response at their cut-off frequency, combined with strong and homogeneous field enhancement along their nanochannels. The CPA conditions are perfectly satisfied at the ENZ frequency, surprisingly by a subwavelength plasmonic structure, resulting in strong CPA under the illumination of two counter-propagating plane waves with appropriate amplitudes and phases. In addition , we inve…
In this paper, tooth-shaped and multiple-teeth-shaped plasmonic filters in the metal-insulator-metal (MIM) waveguides are demonstrated numerically. By introducing a three-port waveguide splitter, a modified model based on the multiple-beam-interference and the scattering matrix is given. The ransmittance spectrum as a function of teeth width, depth, period and period number are respectively addressed. The result shows the new structure not only performs the filtering function as well as MIM grating-like structures, but also is of submicrometer size for ultra-high integration and relatively eas…
We present a joint experimental and theoretical study of the driven Su-Schrieffer-Heeger model implemented by arrays of evanescently coupled plasmonic waveguides. Floquet theory predicts that this system hosts for suitable driving frequencies a topologically protected edge state that has no counterpart in static systems, the so-called anomalous Floquet topological $π$-mode. By using real- and Fourier-space leakage radiation microscopy in combination with edge- and bulk excitation, we unequivocally identify the anomalous Floquet topological $π$-mode and study its frequency dependence.
We propose a plasmonic modulator with semiconductor gain material for optoelectronic integrated circuits. We analyze properties of a finite-thickness metal-semiconductor-metal (F-MSM) waveguide to be utilized as an ultra-compact and fast plasmonic modulator. The InP-based semiconductor core allows electrical control of signal propagation. By pumping the core we can vary the gain level and thus the transmittance of the whole system. The study of the device was made using both analytical approaches for planar two-dimensional case as well as numerical simulations for finite-width waveguides. We a…
The fundamental guided dispersion characteristics of guided light in a subwavelength dielectric slit channel embedded by two different plasmonic metals are investigated when varying the gap width. As a result, an overall and salient picture of the guided dispersion characteristics is obtained over a wide spectrum range below and above the plasma frequencies of the two different plasmonic metals, which is important preliminary information for analyzing this type of subwavelength waveguide. In particular, the effects of using two different metals on the guided mode dispersions are emphasized in …
We develop a self-consistent finite element method to study spontaneous emission at nanoscale proximity of plasmonic waveguides. In the model, it is assumed that only one guided mode is dominatingly excited by the quantum emitter. With such one dominating mode assumption, the cross section of the plasmonic waveguide can be arbitrary. We apply our numerical method to calculate the coupling of a quantum emitter to a cylindrical nanowire and a rectangular waveguide, and compare the cylindrical nanowire to previous work valid in quasistatic approximation. The fraction of the energy coupled to the …
A novel nanometeric plasmonic filter in a tooth-shaped Metal-Insulator-Metal waveguide is proposed and demonstrated numerically. An analytic model based on the scattering matrix method is given. The result reveals that the single tooth-shaped filter has a wavelength filtering characteristic and an ultra-compact size in the length of a few hundred nanometers, compared to grating-like SPPs filters. Both analytic and simulation results show that the wavelength of the trough of the transmission has linear and nonlinear relationships with the tooth depth and the tooth width, respectively. The waveg…
For the purpose of using plasmonics in an integrated scheme where single emitters can be probed efficiently, we experimentally and theoretically study the scattering properties of single nano-rod gold antennas as well as antenna arrays placed on one-dimensional dielectric silicon nitride waveguides. Using real space and Fourier microscopy correlated with waveguide transmission measurements, we quantify the spectral properties, absolute strength and directivity of scattering. The scattering processes can be well understood in the framework of the physics of dipolar objects placed on a planar la…
Plasmonic waveguides are a promising platform for integrated nanophotonic circuits and nanoscale quantum optics. Their use is however often hampered by the limited propagation length of the guided surface plasmon modes. A detailed understanding of the influence of the material quality and the waveguide geometry on the complex mode index is therefore crucial. In this letter, we present interferometric near-field measurements at telecommunication wavelength on plasmonic slot waveguides fabricated by focused ion beam milling in single- and poly-crystalline gold films. We observe a significantly b…
We propose and design an ultra-compact and broadband tunable multimode interference (MMI) splitter in mid-infrared based on graphene plasmonic waveguides. The size of the device is only 0.56μm*1.2μm, which corresponds to device area of only about 0.014λ^2, where λ is the vacuum wavelength. And the center wavelength of the device can be tuned in a broad band from 7μm to 9μm with the Fermi level of graphene varied from 0.5eV to 1eV. Furthermore, the device is easy to be fabricated on chip.
We demonstrate the suppression of crosstalk between two dielectric nanowaveguides by placing an auxiliary linear waveguide between loaded waveguides spaced by one wavelength. The total cross-sectional dimension of the system containing two transmission lines is less than two microns that is hundred times smaller than a cross-section of a system made of dielectric fiber. The propagating modes in these waveguides are the sum and the difference of symmetric and antisymmetric modes of the coupled system. Crosstalk is suppressed by matching the wavenumbers of these modes. The analytically obtained …
We investigate plasmonic modulators with a gain material to be implemented as ultra-compact and ultra-fast active nanodevices in photonic integrated circuits. We analyze metal-semiconductor-metal (MSM) waveguides with InGaAsP-based active material layers as ultra-compact plasmonic modulators. The modulation is achieved by changing the gain of the core that results in different transmittance through the waveguides. A MSM waveguide enables high field localization and therefore high modulation speed. Bulk semiconductor, quantum wells and quantum dots, arranged in either horizontal or vertical lay…
We derive general coupled-mode equations describing the nonlinear interaction of electromagnetic modes in media with loss and gain. Our approach is rigorously based on the Lorentz reciprocity theorem, and it can be applied to a broad range of metal-dielectric photonic structures, including plasmonic waveguides and metamaterials. We verify that our general results agree with the previous analysis of particular cases, and predict novel effects on self- and cross-phase modulation in multi-layer nonlinear fishnet metamaterials.
We propose a scheme to realize nonlinear coherent perfect absorption (CPA) at the nanoscale using epsilon-near-zero (ENZ) plasmonic waveguides. The general conditions to achieve CPA in a linear ENZ plasmonic waveguide are analyzed and presented. The proposed ENZ waveguides support an effective ENZ response at their cut-off frequency, where the CPA effect occurs under the illumination of two counter-propagating plane waves with equal amplitudes and appropriate phase distributions. In addition, the strong and uniform field enhancement inside the nanochannels of the waveguides at the ENZ resonanc…
The hybrid plasmonic waveguide consists of a high-permittivity dielectric nanofiber embedded in a low-permittivity dielectric near a metal surface. This architecture is considered as one of the most perspective candidates for long-range subwavelength guiding. We present qualitative analysis and numerical results which reveal advantages of the special waveguide design when dielectric constant of the cylinder is greater than the absolute value of the dielectric constant of the metal. In this case the arbitrary subwavelength mode size can be achieved by controlling the gap width. Our qualitative …
Nanoparticle chain waveguide based on negative-epsilon material is investigated through a generic 3D finite-element Bloch-mode solver which derives complex propagation constant ($k$). Our study starts from waveguides made of non-dispersive material, which not only singles out "waveguide dispersion" but also motivates search of new materials to achieve guidance at unconventional wavelengths. Performances of gold or silver chain waveguides are then evaluated; a concise comparison of these two types of chain waveguides has been previously missing. Beyond these singly-plasmonic chain waveguides, w…
We theoretically investigate a nanoscale mode-division multiplexing scheme based on parity-time (PT) symmetric coaxial plasmonic waveguides. Coaxial waveguides support paired degenerate modes corresponding to distinct orbital angular momentum states. PT symmetric inclusions of gain and loss break the degeneracy of the paired modes and create new hybrid modes without orbital angular momentum. This process can be made thresholdless by matching the mode order with the number of gain and loss sections within the coaxial ring. Using both a Hamiltonian formulation and degenerate perturbation theory,…
We demonstrate experimentally the resonant extinction of THz radiation by a single plasmonic bowtie antenna, formed by two n-doped Si monomers with a triangular shape and facing apexes. This demonstration is achieved by placing the antenna at the output aperture of a conically tapered waveguide, which enhances the intensity of the incident THz field at the antenna position by a factor 10. The waveguide also suppresses the background radiation that otherwise is transmitted without being scattered by the antenna. Bowtie antennas, supporting localized surface plasmon polaritons, are relevant due …
We analytically derive a rigorous expression for the relative impedance ratio between two photonic structures based on their electromagnetic interaction. Our approach generalizes the physical meaning of the impedance to a measure for the reciprocity-based overlap of eigenmodes. The consistence with known cases in the radiofrequency and optical domain is shown. The analysis reveals where the applicability of simple circuit parameters ends and how the impedance can be interpreted beyond this point. We illustrate our approach by successfully describing a Bragg reflector that terminates an insulat…
We propose several planar layouts of ultra-compact plasmonic waveguide modulators that utilize alternative CMOS-compatible materials. The modulation is efficiently achieved by tuning the carrier concentration in a transparent conducting oxide layer, thereby tuning the waveguide either in plasmonic resonance or off-resonance. Resonance significantly increases the absorption coefficient of the plasmonic waveguide, which enables larger modulation depth. We show that an extinction ratio of 86 dB/um can be achieved, allowing for a 3-dB modulation depth in less than one micron at the telecommunicati…
A method for the substantial reduction of propagation loss of surface plasmons was proposed and experimentally demonstrated. The method is based on the fact that the propagation loss of the surface plasmons depends significantly on the optical confinement of the plasmon. A plasmonic structure, which contains a metal and two dielectric layers of different refractive indexes, is proposed in order to optimize optical confinement and to reduce propagation loss of the surface plasmons. A low propagation loss of 0.17 dB/um for a surface plasmon in a Fe/MgO/AlGaAs plasmonic structure was achieved. A …
We theoretically investigate the properties of crossing for two perpendicular subwavelength plasmonic slot waveguides. We show that, when encountering nano intersection, the crosstalk for the direct crossing is around 25%, almost same as throughout. In terms of symmetry considerations and resonant-tunnelling effect, we design compact cavity-based structures. Our results show that the crosstalk is eliminated and the throughput reaches the unity on resonance. Simulations results are in agreement with those from the coupled-model theory. When taking into account of the material loss, due to the u…
In atomic multi-level systems, adiabatic elimination is a method used to minimize complicity of the system by eliminating irrelevant and strongly coupled levels by detuning them from one-another. Such a three-level system, for instance, can be mapped onto physical in form of a three-waveguide system. Actively detuning the coupling strength between the respective waveguide modes allows modulating light propagating through the device, as proposed here. The outer waveguides act as an effective two- photonic-mode system similar to ground- and excited states of a three-level atomic system, whilst t…
Enhancement of magneto-optical effects in hybrid magneto-plasmonic systems has attracted considerable recent attention owing to their potential for building non-reciprocal nanophotonic devices. Quantitative understanding on the fundamental origin and contributing mechanisms for the enhancement is extremely crucial for optimizing applications. Here, we unravel the distinctly different physical origin of the giant enhancement of Faraday rotation and ellipticity in a hybrid magneto-plasmonic system, namely, waveguided magneto-plasmonic crystal for excitation with transverse electric (TE) and tran…
Plasmonic antennas integrated on silicon devices have large and yet unexplored potential for controlling and routing light signals. Here, we present theoretical calculations of a hybrid silicon-metallic system in which a single gold nanoantenna embedded in a single-mode silicon waveguide acts as a resonance-driven filter. As a consequence of scattering and interference, when the resonance condition of the antenna is met, the transmission drops by 85% in the resonant frequency band. Firstly, we study analytically the interaction between the propagating mode and the antenna by including radiativ…
We evaluate the sensing properties of plasmonic waveguide sensors by calculating their resonant transmission spectra in different regions of the non-Hermitian eigenmode space. We elucidate the pitfalls of using modal dispersion calculations in isolation to predict plasmonic sensor performance, which we address by using a simple model accounting for eigenmode excitation and propagation. Our transmission calculations show that resonant wavelength and spectral width crucially depend on the length of the sensing region, so that no single criterion obtained from modal dispersion calculations alone …
Coupling of light into a thin layer of high refractive index material by plasmonic nanoparticles has been widely studied for application in photovoltaic devices, such as thin-film solar cells. In numerous studies this coupling has been investigated through measurement of e.g. quantum efficiency or photocurrent enhancement. Here we present a direct optical measurement of light coupling into a waveguide by plasmonic nanoparticles. We investigate the coupling efficiency into the guided modes within the waveguide by illuminating the surface of a sample, consisting of a glass slide coated with a hi…
