We show that a metallic plate with fractal-shaped slits can be homogenitized as a plasmonic metamaterial with plasmon frequency dictated by the fractal geometry. Owing to the all-dimensional subwavelength nature of the fractal pattern, our system supports both transverse-electric and transverse-magnetic surface plasmons. As a result, this structure can be employed to focus light sources with all-dimensional subwavelength resolutions and enhanced field strengths. Microwave experiments reveal that the best achievable resolution is only, and simulations demonstrate that similar effects can be realized at infrared frequencies with appropriate designs.
The guided dispersion characteristics of subwavelength nanoscale plasmonic coaxial lines are analyzed in detail over a wide optical frequency range below the plasma frequency with a varying gap between the inner and outer plasmonic conductors, providing important preliminary information for understanding the guided mode characteristics of subwavelength nanoscale coaxial lines with plasmonic metals. In particular, when the inner or outer radius is varied, guided modes with similar and dissimilar dispersive features are obtained and discussed. A brief comparison of the propagating modes for the …
Metal-dielectric multilayer metamaterials with extreme loss-anisotropy, in which the longitudinal component of the permittivity tensor has ultra-large imaginary part, are proposed and designed. Diffraction-free deep subwavelength beam propagation and manipulation, due to the nearly flat iso-frequency contour (IFC), is demonstrated in such loss-anisotropic metamaterials. It is also shown that deep subwavelength beam propagation can be realized in practical multilayer structures with large multilayer period, when the nonlocal effect is considered.
We study the eigenmodes of a slab of a wire metamaterial and demonstrate that such a waveguiding structure supports deep-subwavelength propagating modes exhibiting properties of a single-mode waveguide at any fixed frequency below the plasma frequency of metal wires. We compare our analytical results with the dispersion relations extracted from the experimental measurements.
We analyze nonlinear effects in optically driven arrays of nonlinear metallic nanoparticles. We demonstrate that such plasmonic systems are characterized by a bistable response, and they can support the propagation of dissipative switching waves (or plasmonic kinks) connecting the states with different polarization. We study numerically the properties of such plasmonic kinks which are characterized by a subwavelength extent and a tunable velocity.
We present plasmonic Bragg reflectors for increasing the extraordinary optical transmission through periodic arrays of subwavelength apertures in a metal film. The increase in transmission arises by preventing loss at the edges of the array. The plasmonic Bragg reflectors have periodicity of half the usual array's periodicity. Nano-hole arrays flanked thus by reflectors exchibited double the transmission as compared to the arrays without reflectors. These structures may also be used to isolate devices in plasmonic integrated circuits.
A type of tunable plasmonic lens with nanoslits is proposed for subwavelength imaging in the far field at different wavelengths. The nanoslits array in the plasmonic lens, which have constant depths but varying widths, could generate desired optical phase retardations based on the particular propagation property of the Surface Plasmon Polaritons (SPPs) in the metal-dielectric-metal (MDM) slit waveguides. We theoretically and numerically demonstrate the tunability of a single plasmonic lens for subwavelength imaging (full width at half maximum, 0.37 ~0.47) by adjusting the surrounding dielectri…
The exciting discovery of topological condensed matter systems has lately triggered a search for their photonic analogs, motivated by the possibility of robust backscattering-immune light transport. However, topological photonic phases have so far only been observed in photonic crystals and waveguide arrays, which are inherently physically wavelength scaled, hindering their application in compact subwavelength systems. In this letter, we tackle this problem by patterning the deep subwavelength resonant elements of metamaterials onto specific lattices, and create crystalline metamaterials that …
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 …
In this letter, we introduce stacked fishnet metamaterial for steering light in microwave region. We numerically demonstrate that optical Bloch oscillations and a focus of as small as one sixth of a wavelength can be achieved. The flexibility of varying geometrical parameters of the fishnet slabs provides an efficient way for tuning its local effective media parameters and opens the possibility for controlling light arbitrarily. The experiment verifies subwavelength-sized light focusing effect by scanning magnetic field at the surface of the sample directly.
Metal losses affect the performance of every plasmonic or metamaterial structure; dealing with them will determine the degree to which these structures will find practical applications.
We present a theoretical study of the spontaneous emission of a line dipole source embedded in a graphene--coated subwavelength wire of arbitrary shape. The modification of the emission and the radiation efficiencies are calculated by means of a rigorous electromagnetic method based on Green's second identity. Enhancement of these efficiencies is observed when the emission frequency coincides with one of the plasmonic resonance frequencies of the wire. The relevance of the dipole emitter position and the dipole moment orientation are evaluated. We present calculations of the near--field distri…
We demonstrate a metamaterial that cannot be described by a single set of refractive-index and impedance values, even for fixed frequency and polarization. The metamaterial structure is a stack of dissimilar waveguides with subwavelength width and spacing, which guide light at different phase velocities. This multi-refractive-index metamaterial (MRIM) can be viewed as a spatial superposition of multiple homogeneous materials. Using full-wave simulations, we demonstrate several optical components based on MRIMs, including prisms that deflect light to multiple angles, lenses with multiple focal …
We calculate the light transmission by a subwavelength plasmonic array using the boundary element method for parallel cylinders with different cross-sections: circular or elliptic with axes ratio 4:1. We demonstrate that the plasmonic resonance is sharper for the case of ellipses with a large horizontal axis. This structure is susceptible to the refractive index variations of media since the high derivative of reflection and transmission coefficients are near the angle of total internal reflection. To obtain an approximate analytical expression, we use the model of a metallic layer. We explore…
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 …
We demonstrate that under certain conditions, fractional Talbot revivals can occur in heterostructures of composite metamaterials, such as multilayer positive and negative index media, metallodielectric stacks, and one-dimensional dielectric photonic crystals. Most importantly, without using the paraxial approximation we obtain Talbot images for the feature sizes of transverse patterns smaller than the illumination wavelength. A general expression for the Talbot distance in such structures is derived, and the conditions favorable for observing Talbot effects in layered heterostructures is disc…
A plasmonic "molecule" consisting of a radiative element coupled with a sub-radiant (dark) element is theoretically investigated. The plasmonic "molecule" shows close resemblance to the electromagnetically induced transparency (EIT) in an atomic system. Because of its sub-wavelength dimension, this EIT-like "molecule" can be used as building block to construct a "slow light" plasmonic metamaterial.
We develop an approach to utilize anisotropic metamaterials to solve one of the fundamental problems of modern plasmonics -- parasitic scattering of surface waves into free-space modes, opening the road to truly two-dimensional plasmonic optics. We illustrate the developed formalism on examples of plasmonic refractor and plasmonic crystal, and discuss limitations of the developed technique and its possible applications for sensing and imaging structures, high-performance mode couplers, optical cloaking structures, and dynamically reconfigurable electro-plasmonic circuits.
Plasmonics and metamaterials have attracted considerable attention over the past decade, owing to the revolutionary impacts that they bring to both the fundamental physics and practical applications in multiple disciplines. Although the two fields initially advanced along their individual trajectories in parallel, they started to interfere with each other when metamaterials reached the optical regime. The dynamic interplay between plasmonics and metamaterials has generated a number of innovative concepts and approaches, which are impossible with either area alone. This review presents the fund…
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…
We demonstrate polarization controlled absorption in plasmonic bimetallic metamaterials. We fabricate and experimentally characterize Au/Ni ring resonator arrays, where by varying the wavelength and polarization of the incident wave, local electromagnetic fields and dissipation can be suppressed or enhanced in the Au and Ni areas of the rings.
We present a metamaterial-based terahertz (THz) sensor for thickness measurements of subwavelength-thin materials and refractometry of liquids and liquid mixtures. The sensor operates in reflection geometry and exploits the frequency shift of a sharp Fano resonance minimum in the presence of dielectric materials. We obtained a minimum thickness resolution of 12.5 nm (1/16000 times the wavelength of the THz radiation) and a refractive index sensitivity of 0.43 THz per refractive index unit. We support the experimental results by an analytical model that describes the dependence of the resonance…
The light transmission through a dispersive plasmonic circular hole is numerically investigated with an emphasis on its subwavelength guidance. For a better understanding of the effect of the hole diameter on the guided dispersion characteristics, the guided modes, including both the surface plasmon polariton mode and the circular waveguide mode, are studied for several hole diameters, especially when the metal cladding has a plasmonic frequency dependency. A brief comparison is also made with the guided dispersion characteristics of a dispersive plasmonic gap [K. Y. Kim, et al., Opt. Express …
We report that hybridizing semiconductor quantum dots with plasmonic metamaterial leads to a multi-fold intensity increase and narrowing of their photoluminescence spectrum. The luminescence enhancement is a clear manifestation of the cavity quantum electrodynamics Purcell effect that can be controlled by the metamaterial's design. This observation is an essential step towards understanding loss compensation in metamaterials with gain media and for developing metamaterial-enhanced gain media.
Transmission through a subwavelength terahertz fiber, which is positioned in parallel to a frequency selective surface, is studied using several finite element tools. Both the band diagram technique and the port-based scattering matrix technique are used to explain the nature of various resonances in the fiber transmission spectrum. First, we observe that spectral positions of most of the transmission peaks in the port-based simulation can be related to the positions of Van Hove singularities in the band diagram of a corresponding infinite periodic system. Moreover, spectral shape of most of t…
The electromagnetic response of subwavelength wires coated with a graphene monolayer illuminated by a linearly polarized plane waves is investigated. The results show that the scattering and extintion cross-sections of the coated wire can be dramatically enhanced when the incident radiation resonantly excites localized surface plasmons. The enhancements occur for p--polarized incident waves and for excitation frequencies that correspond to complex poles in the coefficients of the multipole expansion for the scattered field. By dynamically tuning the chemical potential of graphene, the spectral…
We theoretically investigate the optical properties of parity-time (PT)-symmetric three dimensional metamaterials composed of strongly-coupled planar plasmonic waveguides. By tuning the loss-gain balance, we show how the initially isotropic material becomes both asymmetric and unidirectional. The highly tunable optical dispersion of PT -symmetric metamaterials provides a foundation for designing an entirely new class of three-dimensional bulk synthetic media, with applications ranging from sub-diffraction-limited optical lenses to non-reciprocal nanophotonic devices.
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.
We investigate the subwavelength imaging capacity of a two-dimensional fanned-out plasmonic waveguide array, formed by air channels surrounded by gold metal layers for operation at near-infrared wavelengths, via finite element simulations. High resolution is achieved on one side of the device by tapering down the channel width while simultaneously maintaining propagation losses of a few dB. On the other, low-resolution side, output couplers are designed to optimize coupling to free space and to minimize channel cross talk via surface plasmons. Point sources separated by λ/15 can still be clear…
The development of responsive metamaterials has enabled the realization of compact tunable photonic devices capable of manipulating the amplitude, polarization, wave vector, and frequency of light. Integration of semiconductors into the active regions of metallic resonators is a proven approach for creating nonlinear metamaterials through optoelectronic control of the semiconductor carrier density. Metal-free subwavelength resonant semiconductor structures offer an alternative approach to create dynamic metamaterials. We present InAs plasmonic disk arrays as a viable resonant metamaterial at t…
We study the physics of a new type of subwavelength nanocavities. They are based on U-shaped metal-insulator-metal waveguides supporting the excitation of surface plasmon polaritons. The waveguides are simultaneously excited from both sides of the U by incident plane waves. Due to their finite length discrete modes emerge within the nanocavity. We show that the excitation symmetry with respect to the cavity ends permits the observation of even and odd modes. Our investigations include near and far field simulations and predict a strong spectral far field response of the comparable small nanore…
We propose and demonstrate subwavelength grating (SWG) metamaterial waveguides and ring resonators on a silicon nitride platform for the first time. The SWG waveguide is engineered such that a large overlap of 53% of the Bloch mode with the top cladding material is achieved, demonstrating excellent potential for applications in evanescent field sensing and light amplification. The devices, which have critical dimensions greater than 100 nm, are fabricated using a commercial rapid turn-around silicon nitride prototyping foundry process using electron beam lithography. Experimental characterizat…
We propose a design for optical-frequency double-negative metamaterials (DMNs) in which the unit cell is formed by a single-layer plasmonic inclusion. By introducing some properly arranged stepwise modulations onto the inclusions, the effective permittivity and permeability of the material may become simultaneously negative due to the excitation of higher-order multipole plamonic (electrostatic) resonances. The approach opens a possibility to construct low-loss optical DNMs with great engineering simplicity.
We demonstrate that plasmonic helical gratings consisting of metallic nanowires imprinted with helical grooves or ridges can be used efficiently to generate plasmonic vortices with radius much smaller than the operating wavelength. In our proposed approach, these helical surface gratings are designed so that plasmon modes with different azimuthal quantum numbers (topological charge) are phase-matched, thus allowing one to generate optical plasmonic vortices with arbitrary topological charge. The general principles for designing plasmonic helical gratings that facilitate efficient generation of…
A metamaterials-based approach to making a wide-angle absorber of infrared radiation is described. The technique is based on an anisotropic Perfectly Impedance Matched Negative Index Material (PIMNIM). It is shown analytically that a sub-wavelength in all three dimensions PIMNIM enables absorption of close to 100% for incidence angles up to $45°$ to the normal. A specific implementation of such frequency-tunable PIMNIM based on plasmonic metamaterials is presented. Applications to infrared imaging and coherent thermal sources are described.
Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear and nonlinear optical properties. We show that the modal overlap of fundamental and second-harmonic light in an anisotropic plasmonic metamaterial slab results in the broadband enhancement of radiated second-harmonic intensity by up to 2 orders of magnitudes for TM- and TE-polarized fundamental light, compared to a smooth Au film under TM-polarised illumination. The results open up possibilities to design tuneable frequency-doubling metamaterial with the goal to overcome limitations associated with c…
Electromagnetic absorbers have drawn increasing attention in many areas. A series of plasmonic and metamaterial structures can work as efficient narrow band absorbers due to the excitation of plasmonic or photonic resonances, providing a great potential for applications in designing selective thermal emitters, bio-sensing, etc. In other applications such as solar energy harvesting and photonic detection, the bandwidth of light absorbers is required to be quite broad. Under such a background, a variety of mechanisms of broadband/multiband absorption have been proposed, such as mixing multiple r…
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 present a theoretical study of plasmonic lattice solitons (PLSs) formed in two-dimensional (2D) arrays of metallic nanowires embedded into a nonlinear medium with Kerr nonlinearity. We analyze two classes of 2D PLSs families, namely, fundamental and vortical PLSs in both focusing and defocusing media. Their existence, stability, and subwavelength spatial confinement are studied in detail.
Noble metals that currently dominate the fields of plasmonics and metamaterials suffer from large ohmic losses. New plasmonic materials, such as doped oxides and nitrides, have smaller material loss, and, using them in place of metals carries promise of reduced-loss plasmonic and metamaterial structures, with sharper resonances and higher field concentration. This promise is put to a rigorous analytical test in this work which reveals that having low material loss is not sufficient to have a reduced modal loss in plasmonic structures. To reduce the modal loss it is absolutely necessary for the…
A tri-layer metamaterial perfect absorber of light, consisting of (Al/ZnS/Al) films with the top aluminium layer patterned as an array of circular disk nanoantennas, is investigated for resonantly enhancing Raman scattering from C-60 fullerene molecules deposited on the metamaterial. The metamaterial is designed to have resonant bands due to plasmonic and electromagnetic resonances at the Raman pump frequency (725 nm) as well as Stokes emission bands. The Raman scattering from C60 on the metamaterial with resonantly matched bands is measured to be enhanced by an order of magnitude more than fr…
We demonstrate that photonic and phononic crystals consisting of closely spaced inclusions constitute a versatile class of subwavelength metamaterials. Intuitively, the voids and narrow gaps that characterise the crystal form an interconnected network of Helmholtz-like resonators. We use this intuition to argue that these continuous photonic (phononic) crystals are in fact asymptotically equivalent, at low frequencies, to discrete capacitor-inductor (mass-spring) networks whose lumped parameters we derive explicitly. The crystals are tantamount to metamaterials as their entire acoustic branch,…
Subwavelength plasmonic waveguides show the unique ability of strongly localizing (down to the nanoscale) and guiding light. These structures are intrinsically two-way optical communication channels, providing two opposite light propagation directions. As a consequence, when light is coupled to these planar integrated devices directly from the top (or bottom) surface using strongly focused beams, it is equally shared into the two opposite propagation directions. Here, we show that symmetry can be broken by using incident circularly polarized light, on the basis of a spin-orbital angular moment…
By embedding four-rod resonators inside double-split ring resonators superlattice, a planar composite metamaterial possessing tripod plasmonic resonances is fabricated. Double Fano resonances are observed where a common subradiant driven oscillator is coupled with two superradiant oscillators. As a classical analogue of four-level tripod atomic system, the transmission spectrum of the composite metamaterial exhibits a double Fano-based coherent effect. Transfer of absorbed power between two superradiant oscillators is controlled by manipulating two coupling strengths conjugated through the pol…
We report extensive enhancement in the refractive index of artificially designed metamaterials by exploiting the deep subwavelength coupling in a free-standing, thin-film metal-dielectric-metal checkboard structure. A record high refractive index of 77.02+43.22i is obtained at terahertz frequencies. The detailed investigations reveal that the enhancement of the effective refractive index of the structure via deep subwavelength coupling in a bilayer design is governed by a power law, which is an effective and simpler approach to design high index metamaterial. The approach relies on deep subwav…
We predict theoretically that stable subwavelength plasmonic lattice solitons (PLSs) are formed in arrays of metallic nanowires embedded in a nonlinear medium. The tight confinement of the guiding modes of the metallic nanowires, combined with the strong nonlinearity induced by the enhanced field at the metal surface, provide the main physical mechanisms for balancing the wave diffraction and the formation of PLSs. As the conditions required for the formation of PLSs are satisfied in a variety of plasmonic systems, we expect these nonlinear modes to have important applications to subwavelength…
There has been a surge of interest in the subwavelength confinement of the electromagnetic fields. It is well known that in optics the subwavelength confinement can be obtained due to surface plasmon (quasielectrostatic) oscillations. In this paper we propose to realize the subwavelength confinement in microwaves due to dipolar-mode (quasimagnetostatic) magnon oscillations in ferrite particles. Our studies of interactions between microwave electromagnetic fields and small ferrite particles with magnetic-dipolar-mode (MDM) oscillations show strong localization of electromagnetic energy. MDM osc…
The limited resolution of a conventional optical microscope stems from the fact that the subwavelength information of an object is carried by evanescent waves, which exponentially decays in space and cannot reach the imaging plane. We introduce here a metamaterial solid immersion lens (mSIL), which utilizes closely-packed high-index nanoparticles as a composite media to effectively convert and transport evanescent waves from near-field to far-field. About 20% of evanescent wave energy of an ideal point source can be directed into far-field by mSIL. This has led to the exceptional imaging perfo…
Despite more than a decade of active research, the fundamental problem of material loss remains a major obstacle in fulfilling the promise of the recently emerged fields of metamaterials and plasmonics to bring in revolutionary practical applications. In the present work, we demonstrate that the problem of strong material absorption that is inherent to plasmonic systems and metamaterials based on plasmonic components, can be addressed by utilizing the time dimension. By matching the pulse profile to the actual response of a lossy metamaterial, this approach allows to offset the effect of the m…
We consider a simple configuration for realizing one-dimensional slow-light metamaterials with large bandwidth-delay products using stub-shaped Fabry-Perot resonators as building blocks. Each metaatom gives rise to large group indices due to a classical analog of the dressed-state picture of electromagnetically-induced transparency. By connecting up to eight metaatoms, we find bandwidth-delay products over unity and group indices approaching 100. Our approach is quite general and can be applied to any type of Fabry-Perot resonators and tuned to different operating wavelengths.
We demonstrate resonant Faraday polarization rotation in plasmonic arrays of bimetallic nano-ring resonators consisting of Au and Ni sections. This metamaterial design allows to optimize the trade-off between the enhancement of magneto-optical effects and plasmonic dissipation. Although Ni sections correspond to as little as ~6% of the total surface of the metamaterial, the resulting magneto-optically induced polarization rotation is equal to that of a continuous film. Such bimetallic metamaterials can be used in compact magnetic sensors, active plasmonic components and integrated photonic cir…
We use spatially and angle-resolved cathodoluminescence imaging spectroscopy to study, with deep subwavelength resolution, the radiation mechanism of single plasmonic ridge antennas with lengths ranging from 100 to 2000 nm. We measure the antenna's standing wave resonances up to the fifth order and measure the dispersion of the strongly confined guided plasmon mode. By directly detecting the emitted antenna radiation with a 2D CCD camera we are able to measure the angular emission patterns associated with each individual antenna resonance. We demonstrate that the shortest ridges can be modeled…
We analyze, by means of numerical simulations, transmission enhancements through sub- wavelength slits due to the presence of sets of plasmonic nanocylinders, placed near the exit of these apertures. Further, we extend this study to photonic crystals of dipolar plasmonic particles in front of an array of extraordinarily transmitting slits practiced in a metallic slab.
We consider an array of the meta-atom consisting of two cut-wires and a split-ring resonator interacting with an electromagnetic field with two polarization components. We prove that such metamaterial system can be taken as a classical analogue of an atomic medium with a double- $Λ$-type four-level configuration coupled with four laser fields, exhibits an effect of plasmon induced transparency (PIT), and displays a similar behavior of atomic four-wave mixing (FWM). We demonstrate that when nonlinear varactors are mounted onto the gaps of the split-ring resonators the system can acquire giant s…
This commentary aims to expose the fallacy of claiming that a plasmonic silver film superlens is capable to image real subwavelength objects. This lens was proposed by the Berkeley's group who, in their misleading experiment, inappropriately regarded subwavelength apertures as the objects to be imaged whereas the main function of these apertures was to transform free space laser light into an evanescent field necessary for exciting the surface plasmon resonance phenomenon in silver. In addition, the apertures also determined the constrained effective area on the silver film where the phenomeno…
Photoelectric properties of metamaterials containing non-centrosymmetric, similarly oriented metallic nanoparticles embedded in a homogeneous semiconductor matrix are theoretically studied. Due to the asymmetric shape of the nanoparticle boundary, photoelectron emission acquires a preferred direction, resulting in a photocurrent flow in that direction when nanoparticles are uniformly illuminated by a homogeneous plane wave. This effect is a direct analogy of the photogalvanic (or bulk photovoltaic) effect known to exist in media with non-centrosymmetric crystal structure, such as doped lithium…
Optical manipulation has attracted remarkable interest owing to its versatile and non-invasive nature. However, conventional optical trapping remains inefficient for the nanoscopic world. The emergence of plasmonics in recent years has brought a revolutionary change in overcoming limitations due to diffraction and the requirements for high trapping laser powers. Among the near-field optical trapping cavity-based systems, Fano resonant optical tweezers have a robust trapping capability. In this work, we experimentally demonstrate sequential trapping of 20 nm particles through the use of metamat…
In this paper, we present the design of cylindrical and spherical electromagnetic cloaks working at visible frequencies. The cloak design is based on the employment of layered structures consisting of alternating plasmonic and non-plasmonic materials and exhibiting the collective behavior of an effective epsilon-near-zero material at optical frequencies. The design of a cylindrical cloak to hide cylindrical objects is firstly presented. Two alternative layouts are proposed and both magnetic and non-magnetic objects are considered. Then, the design of spherical cloaks is also presented. The ful…
We suggest a novel approach for generating second-harmonic radiation in subwavelength graphene waveguides. We demonstrate that quadratic phase matching between the plasmonic guided modes of different symmetries can be achieved in a planar double-layer geometry when conductivity of one of the layers becomes spatially modulated. We predict theoretically that, owing to graphene nonlocal conductivity, the second-order nonlinear processes can be actualized for interacting plasmonic modes with an effective grating coupler to allow external pumping of the structure and output of the radiation at the …
From the demonstration of saturable absorption by Vavilow and Levshin in 1926, and with invention of the laser, unavailability of strongly nonlinear materials was a key obstacle for developing optical signal processing, in particular in transparent telecommunication networks. Today, most advanced photonic switching materials exploit gain dynamics and near-band and excitonic effects in semiconductors, nonlinearities in organic media with weakly-localized electrons and nonlinearities enhanced by hybridization with metamaterials. Here we report on a new type of artificial nonlinearity that is nan…
