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Manipulation of nano-scale objects by engineering the electromagnetic waves in the environment medium is pivotal for several particle handling techniques using optical resonators, waveguiding, and plasmonic devices. In this Letter, we theoretically demonstrate the possibility of engineering a compact and tunable plasmon-based terahertz (THz) tweezer using a graphene monolayer that is deposited on a high-index dielectric substrate. When a nanoparticle located in a vacuum in the vicinity of the graphene monolayer is illuminated under total internal reflection, as light is launched from the substrate, such a device is shown to be capable of inducing an enhanced rotating dipole in the nanoparticle thus enabling asymmetric, directional near-field coupling into the graphene plasmon mode and the radiative modes in the substrate. As a result of the total momentum conservation, the net force exerted on the particle points in a direction opposite to the pushing scattering force of the exciting evanescent field. Our results can contribute to novel realizations of photonic devices based on polarization-dependent interactions between nanoparticles and electromagnetic mode fields.

We propose an axisymmetric silicon nanoresonator with designed tapered angle well for the extraordinary enhancement of the decay rate of magnetic dipole (MD) emitters. Due to the resonant coupling of a MD emitter and the MD mode of the subwavelength resonator, the Purcell factor (PF) can easily reach 500, which is significantly higher than the PF when using a silicon nanosphere of the same size. The PF and the resonance frequency are conveniently tuned through the resonator diameter and the taper angle of the blind hole. When supported by a metallic substrate, further enhancement ($$>10^3$$ > 10 3 ) of the MD spontaneous emission is triggered by an image-induced quadrupolar high-Q mode of the nanoantenna. For the sake of comparison we include a critical analysis of the canonical problem that considers a Si spherical shell. Our results might facilitate a novel strategy for promising realizations of chip-scale nanophotonic applications.

The force on a dielectric nano particle close to graphene sheet covering a plane dielectric sustrate is analyzed. We illustrate large pulling force due to the self-action effect of the particle through the graphene interface.

Plasmonic substrates are widely reported for their use in the manipulation of sub-wavelength particles. Here we analyze the optical force in the terahertz (THz) spectrum acting on a dielectric nanoparticle when located close to a graphene monolayer. When lying on a dielectric planar substrate, the graphene sheet enables the nano-sized scatterer to excite a surface plasmon (SP) well confined on the dielectric surface. Under quite general conditions, large pulling forces can be exerted on the particle as a consequence of conservation of linear momentum and a self-action effect. Our results show that the pulling force intensity critically depends on the particle shape and orientation. The low heat dissipation of graphene SPs paves the way for the development of a novel plasmonic tweezer for applications involving biospecimen manipulation in the THz region.

The ability to control optomechanical interactions at subwavelength levels is of key relevance in modern optics. The present work focuses on the improvement of the force exerted on a dielectric nanoparticle placed near an attenuated total reflection structure containing graphene. Our results show that this force is highly dependent on the angle of incidence of the impinging plane wave, and it can be enhanced by nearly three orders of magnitude when this angle coincides with that of the critical total internal reflection and that corresponding to the excitation of surface plasmons along the graphene layer. New effects are found in these angular regions where the induced elliptical polarizability on the nanoparticle provides an asymmetric excitation of electromagnetic modes that generates a pulling (attractive) component whose magnitude is comparable to that of the pushing (repulsive) force provided by the incident field. As a consequence and contrary to what happens for large separation distances, an asymmetric response with respect to the angle of incidence arises for short distances for which the force on the particle is described by curves having a maximum and a minimum. Our results can contribute to a better understanding of polarization dependent interactions between nanoparticles and electromagnetic mode fields for taking advantage of them in nanoparticle manipulation applications.

The coherent anti-Stokes Raman spectroscopy (CARS) techniques are recognized for their ability to detect and identify vibrational coherent processes down to the single-molecular levels. Plasmonic oligomers supporting full-range Fano-like line profiles in their scattering spectrum are one of the most promising class of substrates in the context of surface-enhanced (SE) CARS application. In this work, an engineered assembly of metallic disk-shaped nanoparticles providing two Fano-like resonance modes is presented as a highly-efficient design of SECARS substrate. We show that the scattering dips corresponding to the double-Fano spectral line shapes are originated from the mutual interaction of electric and toroidal dipole moments, leading to the so-called non-trivial first- and second-order anapole states. The anapole modes, especially the higher-order ones, can result in huge near-field enhancement due to their light-trapping capability into the so-called “hot spots”. In addition, independent spectral tunability of the second Fano line shape is exhibited by modulating the gap distance of the corner particles. This feature is closely related to the electric current loop associated with the corner particles in the second-order anapole state and provides a simple design procedure of an optimum SECARS substrate, where the electric field hot spots corresponding to three involved wavelengths, i.e., anti-Stokes, pump, and Stokes, are localized at the same spatial position. These findings yield valuable insight into the plasmonic substrate design for SECARS applications as well as for other nonlinear optical processes, such as four-wave mixing and multi-photon surface spectroscopy.

The ability to control the laser modes within a subwavelength resonator is of key relevance in modern optoelectronics. This work deals with the theoretical research on optical properties of a PT-symmetric nano-scaled dimer formed by two dielectric wires, one is with loss and the other with gain, wrapped with graphene sheets. We show the existence of two non-radiating trapped modes which transform into radiating modes by increasing the gain–loss parameter. Moreover, these modes reach the lasing condition for suitable values of this parameter, a fact that makes these modes achieve an ultra high quality factor that is manifested on the response of the structure when it is excited by a plane wave. Unlike other mechanisms that transform trapped modes into radiating modes, we show that the variation of gain–loss parameter in the balanced loss–gain structure here studied leads to a variation in the phase difference between induced dipole moments on each wires, without appreciable variation in the modulus of these dipole moments. We provide an approximated method that reproduces the main results provided by the rigorous calculation. Our theoretical findings reveal the possibility to develop unconventional optical devices and structures with enhanced functionality.

Manipulation of the exciton emission rate in nanocrystals of lead halide perovskites (LHPs) was demonstrated by means of coupling of excitons with a hyperbolic metamaterial (HMM) consisting of alternating thin metal (Ag) and dielectric (LiF) layers. Such a coupling is found to induce an increase of the exciton radiative recombination rate by more than a factor of three due to the Purcell effect when the distance between the quantum emitter and HMM is nominally as small as 10 nm, which coincides well with the results of our theoretical analysis. Besides, an effect of the coupling-induced long wavelength shift of the exciton emission spectrum is detected and modeled. These results can be of interest for quantum information applications of single emitters on the basis of perovskite nanocrystals with high photon emission rates.

Manipulation of the exciton emission rate in nanocrystals of lead halide perovskites (LHPs) was demonstrated by means of coupling of excitons with a hyperbolic metamaterial (HMM) consisting of alternating thin metal (Ag) and dielectric (LiF) layers. Such a coupling is found to induce an increase of the exciton radiative recombination rate by more than a factor of three due to the Purcell effect when the distance between the quantum emitter and HMM is nominally as small as 10 nm, which coincides well with the results of our theoretical analysis. Besides, an effect of the coupling-induced long wavelength shift of the exciton emission spectrum is detected and modeled. These results can be of interest for quantum information applications of single emitters on the basis of perovskite nanocrystals with high photon emission rates.

In this paper, the hybridized localized surface plasmon resonances (LSPRs) of a periodic assembly of graphene-wrapped nanoparticles are used to design a nanoparticle assisted optical absorber. Bandwidth enhancement of this structure via providing multiple types of plasmonic resonances in the associated unit cell using two densely packed crossly stacked graphene strips is proposed. The designed graphene strips support fundamental propagating surface plasmons on the ribbons, and gap plasmons in the cavity constructed by the adjacent sections. Graphene strips exhibit a hyperbolic dispersion region in the operating spectrum and assist in the bandwidth enhancement. Moreover, since the nanoparticles are deposited on the top strips, real-time biasing of them can be easily conducted by exciting the surface plasmons of the strip without the necessity to electrically connect the adjacent nanoparticles. The overall dynamic bandwidth of the structure, using a two-state biasing scheme, covers the frequencies of 18.16–40.47 THz with 90% efficiency. Due to the symmetry of the structure, the device performs similarly for both transverse electric (TE) and transverse magnetic (TM) waves and it has a high broadband absorption rate regarding different incident angles up to 40°. Due to the presence of 2D graphene material and also using hollow spherical particles, our proposed absorber is also lightweight and it is suitable for novel compact optoelectronic devices due to its sub-wavelength dimensions.

Epsilon-near-zero (ENZ) materials, including artificial metamaterials, have been advanced to mold laser beams and antenna-mediated radiated waves. Here we propose an efficient method to control Ohmic losses inherent to natural ENZ materials by the assembly of subwavelength structures in a nonperiodic matrix constituting an ENZ metacoating. Implemented over plano-concave transparent substrates whose radius can be of only a few wavelengths, ENZ surface-relief elements demonstrate to adequately shape a plane wave into highly localized fields. Furthermore, our proposal provides an energy efficiency even higher than an ideally-lossless all-ENZ plano-concave lens. Our procedure is satisfactory to generate aberration-free nonparaxial focused waves and accelerating beams in miniaturized spaces.

In this paper we show that engineering both phase and amplitude of the scattered light can be employed in designing metalenses with either higher resolution or apodized focal spots. C-shaped split-ring micro-resonators (CSRRs) with different geometrical parameters are selected to have a full control of amplitude and phase. While phase engineering is necessary for light focusing, amplitude modulation of the scattered wave can be applied to characterize the focal point properties such as resolution gain and sidelobe level. We show that both axial and transverse resolution improvement or apodization is possible in the far-field region by applying proper amplitude function. Amplitude modulation technique, which is introduced in this paper, paves a new way to design efficient lenses which can be utilized in imaging and lithography applications in all frequency ranges.

In this paper, a 3D sub-wavelength graphene-coated nano-disk dimer (GDD) is proposed for multi-frequency giant near-field enhancement. We observed that the dual-band operation originates from the excitation of hybridized localized surface plasmons on top and bottom faces of the disks along with the mutual coupling from the adjacent particle. Due to the sub-wavelength nature of the disks, the excited localized surface plasmons on the sidewalls are weak but they still can affect the dual operating bands. On the other hand, the strength and resonance frequency of the enhanced fields can be simply modulated by tuning the relative distances of 2D graphene disks on top and bottom faces. Adjustable dual-band performance is hardly attainable using simplified 2D graphene disks, however, it naturally comes out through modal hybridization in the subwavelength 3D structure containing multiple resonant units. Our suggested configuration has better optical properties than its noble metal counterparts because of its higher field enhancement and lower ohmic losses. Moreover, the electromagnetic response is reconfigurable by varying the bias voltage. The influence of graphene quality, chemical potential, and dimer gap size on the electric field enhancement and the resonance frequency of the surface plasmons are investigated, as well. To further improve its performance, a double negative metamaterial core is considered. This mechanism of the performance improvement by the core material is feasible thanks to the 3D nature of the structure. Two possible applications of the presented design are in Surface-Enhanced Raman Spectroscopy (SERS) and optical absorbers.

Metasurfaces, the 2D form of metamaterials with their ability in phase, amplitude and polarization manipulation are widely used in designing optical devices. Efforts to find proper photonic components in the terahertz (THz) range of frequency lead us to adopt metasurfaces as their constituent elements. Here, we conceived a broadband THz lens with an adjustable number and arrangement of focal points. To have a full control over the lens functionality, we used a metasurface with the capability of simultaneously modulating the amplitude and phase of the incident wave. C-shaped ring resonators (CSRRs) with different geometry and orientation capable of simultaneously manipulating phase and amplitude of the scattered fields, are proper choice to design the lens. We show that the introduced lens in a one-dimensional layout has a wide range of working frequencies within the THz spectrum, which can be used in a plethora of applications.

Here we examine Dyakonov-like surface waves (DSWs) in the THz regime traveling along the plane interface between a non-conducting isotropic medium and a low-loss graphene-based uniaxial metamaterial with the optic axis (OA) oriented along with the interface. New insights concerning the propagation characteristics of DSWs are given by analyzing the dispersion relation in such configuration, that is evaluated using the effective medium theory. The range of angles with respect to the OA which is determined for the in-plane wave vector can be conveniently tuned with extremely flexibility in opposition with DSWs excited in natural anisotropic media. The properties discussed here are of relevance in applications reaching ultra-compact electromagnetic waveguides and bio- and chemo-sensing.

Dyadic Green's function for a multilayered spherical structure with alternating graphene-dielectric shells is extracted in this paper. To this end, the unknown expansion coefficients of the scattering superposition method are obtained by considering graphene local surface currents at the interface of two adjacent layers. To validate the formulas, the procedure of Mie scattering analysis employing our formulas is clarified and the extinction efficiencies of various graphene-based nanoparticles are computed. The possibility of using the proposed structure in the design of multi-band optical absorbers is discussed in detail. Moreover, a closed-form formula for obtaining the Purcell factor of a radial dipole emitter in the presence of a graphene-based layered sphere is introduced. The analysis is followed by an example illustrating the possibility of dual-band enhancement of the Purcell factor using a graphene-based core-shell particle. Finally, the procedure of calculating the energy transfer between the donor-acceptor pairs with arbitrary locations are clarified. The research can be potentially used in the fast and efficient analysis of a wide class of novel optical devices with the arbitrary source of excitation.

Theoretical research on localized surface plasmons (LSPs) supported by a structure formed by two parallel dielectric wires with a circular cross section wrapped with a graphene sheet has an impact in the practical realm. Here, LSPs are represented in the form of an infinite series of cylindrical multipole partial waves linked to each of the graphene wires. To obtain the kinematics (complex eigenfrequencies) and dynamic characteristics (field distributions) of the LSPs, we consider the analytic extension to the complex plane of the solution to the boundary value problem. The lower frequency LSP group is formed by four branches, two of them corresponding to bright modes and the others to dark modes. By tuning the chemical potential of the graphene covers so that the dimer symmetry breaks, these dark modes are transformed into resonant observables that can be excited by plane wave incidence.

We theoretically study the electromagnetic energy transfer between donor and acceptor molecules near a graphene waveguide (WG). The surface plasmons (SPs) supported by the structure provide decay channels which lead to an improvement in the energy transfer rate when the donor and acceptor are localized on the same side or even on opposite sides of the WG. The modification of the energy transfer rate compared to its value in absence of the WG are calculated by deforming the integration path into a suitable path in the complex plane. Our results show that this modification is dramatically enhanced when the symmetric and antisymmetric SPs are excited. Notable effects on the spatial dependence of the energy transfer due to the coherent interference between these SP channels, which can be tuned by chemical potential variations, are highlighted and discussed in terms of SP propagation characteristics. Fil: Olivo, Julieta Verónica. Universidad Nacional de Río Cuarto; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Zapata Rodríguez, Carlos J.. Universidad de Valencia; España Fil: Cuevas, Mauro. Universidad de Belgrano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

In this communication, we integrate an active planar waveguide on a birefringent substrate to show experimental evidence of a selective propagation of the spontaneous emission into the propagating. An anisotropic response with significantly-reduced directional excitation along the optic axis as compared with its perpendicular direction is observed. We additionally provide a theoretical modal analysis of the planar microstructure, which is in good agreement with our experimental results.

The title “Dyakonov surface waves: anisotropy enabling confinement on the edge” plainly sets the scope for this chapter. The focus here is on the formation of bounded waves at the interface of two distinct media, at least one of them exhibiting optical anisotropy, which are coined as Dyakonov surface waves (DSWs) in recognition to the physicist who reported their existence for the first time. First, the general aspects of the topic are discussed. It also treats the characterization of bounded waves in isotropic-uniaxial multilayered structures, allowing not only the derivation of the dispersion equation of DSWs but also that of surface plasmons polaritons (SPPs), for instance. Furthermore, the interaction of such surfaces waves, with the possibility of including guided waves in a given planar layer and external sources mimicking experimental setups, can be accounted for by using the transfer matrix formalism introduced here. Finally, special attention is devoted to hyperbolic media with indefinite anisotropy-enabling hybridized scenarios integrating the prototypical DSWs and SPPs. This chapter was supported by the Qatar National Research Fund (Grant No. NPRP 8-028-1-001) and the Spanish Ministry of Economy and Competitiveness (Grants No. TEC2014-53727-C2-1-R and TEC2017-86102-C2-1R).

We propose a simple yet efficient method for generating in-plane hollow beams with a nearly full circular light shell without the contribution of backward propagating waves. The method relies on modulating the phase in the near field of a centrosymmetric optical wave front, such as that from a high-numerical-aperture focused wave field. We illustrate how beam acceleration may be carried out by using an ultranarrow non-flat meta-surface formed by engineered plasmonic nanoslits. A mirror-symmetric, with respect to the optical axis, circular caustic surface is numerically demonstrated that can be used as an optical bottle. This research was funded by the Spanish Ministry of Economy and Competitiveness under the Project TEC2013-50416-EXP. M. Naserpour acknowledges financial support from the Ministry of Science, Research and Technology of Iran.

Spatially accelerating beams are non-diffracting beams whose intensity is localized along curvilinear trajectories, also incomplete circular trajectories, before diffraction broadening governs their propagation. In this paper we report on numerical simulations showing the conversion of a high-numerical-aperture focused beam into a nonparaxial shape-preserving accelerating beam having a beam-width near the diffraction limit. Beam shaping is induced near the focal region by a diffractive optical element that consists of a non-planar subwavelength grating enabling a Bessel signature. This research was funded by the Spanish Ministry of Economy and Competitiveness under the project TEC2011-29120-C05-01. M. Naserpour acknowledges financial support from the Ministry of Science, Research and Technology of Iran.

We investigate, both theoretically and numerically, a graphene-coated nano-cylinder illuminated by a plane electromagnetic wave in the far-infrared range of frequencies. We have derived an analytical formula that enables fast evaluation of the spectral window with a substantial reduction in scattering efficiency for a sufficiently thin cylinder. This polarization-dependent effect leads to tunable resonant invisibility that can be achieved via modification of graphene chemical potential monitored by the gate voltage. A multi-frequency cloaking mechanism based on dimer coated nanowires is also discussed in detail.

Dielectric microlenses employed in imaging and focusing for optoelectronics are currently prospects to be substituted by metalenses showing an extraordinary optical performance within notably reduced volumes. Here we present some proposals to achieve an enhanced resolution in metallodielectric metasurface-based lenses established on either efficient arrangements with high numerical aperture or spatial filtering enabling to surpass the limit of resolution derived by the Rayleigh criterion.

The evaluation of vector wave fields can be accurately performed by means of diffraction integrals, differential equations and also series expansions. In this paper, a Bessel series expansion which basis relies on the exact solution of the Helmholtz equation in cylindrical coordinates is theoretically developed for the straightforward yet accurate description of low-numerical-aperture focal waves. The validity of this approach is confirmed by explicit application to Gaussian beams and apertured focused fields in the paraxial regime. Finally we discuss how our procedure can be favorably implemented in scattering problems.

To focus the incident light, both convex metalenses with hyperbolic phase profile and autofocused Airy (AFA) beams are widely used. To obtain AFA-based bifocal metalenses, we propose two methods in this article. One is to bring the two conjugate focal points of an AFA beam into the real space by applying a proper convex lens phase profile. The other is to use the inefficient central space between the two launched Airy beams with zero amplitude and constant phase profile as an independent metalens. We also show that combining the two introduced methods, leads the design to upgrade to a multifocal structure.

A cylindrical multilayered structure with three coupled graphene shells is shown to behave as a dual-band super-scatterer at mid-infrared frequencies. Under the 2D plasmonic nature of graphene material, multiple scattering resonances are attained in the deep subwavelength regime using an isotropic material. In the proposed structure, we efficiently exploit the existing three plasmonic resonances in each scattering channel. These resonances are tailored by dispersion engineering, which is simply displayed through the Bohr model applied to the associated planar structure. For the super-scatterer design, it is essential that the resonances of multiple channels coincide in a single frequency. Here, for the dual-band performance, the second and third dipole resonances coincide with the first and second quadruple resonances, respectively. A refinement algorithm is developed to obtain the final design parameters. Our strategy offers various degrees of freedom to be tuned in order to control the target working frequency. Our proposed structures have potential applications in the field of imaging, cloaking, biomedicine, solar cells, and optical antennas with improved sensitivity and accuracy due to multiband operation.

We investigate the localization properties of surface waves created at the interface between a truncated 1D photonic crystal and homogeneous medium in the presence of a chiral cap layer using the transfer matrix method. The numerical results show that the interface can support surface waves with both transverse electric and transverse magnetic polarizations. We demonstrate that the surface waves can be engineered by varying the chirality parameter of the cap layer, which plays an important role in controlling and localization of surface states. It is shown that the effect of a chirality parameter on surface waves with transverse electric polarization is more remarkable compared with surface waves with transverse magnetic polarization. In addition, the effect of thickness and material type of the cap layer and the termination layer of a photonic crystal on surface waves is investigated. The results show that these parameters have considerable effect on modification of surface states. These findings may open new opportunities in the design of cavity-based devices such as high-Q sensors and perfect absorbers.

In this paper, we explored the scattering behavior of thin cylinders made of a left-handed material (LHM) and coated by a monoatomic graphene layer. A spectral tunability of the resonance peaks is evidenced by altering the chemical potential of the graphene coating, a fact that occurs at any state of polarization of the incident plane wave in opposition to the case of scatterers of dielectric core. On the contrary, no invisibility condition can be satisfied for dielectric environments. A singular performance is also found for cylinders with permittivity and permeability near zero. Practical implementations of our results can be carried out in sensing and wave manipulation driven by metamaterials.

Engineered core-shell cylinders are good candidates for applications in invisibility and cloaking.In particular, hyperbolic nanotubes demonstrate tunable ultra-low scattering cross section in the visible spectral range. In this work we investigate the limits of validity of the condition for invisibility, which was shown to rely on reaching an epsilon near zero in one of the components of the effective permittivity tensor of the anisotropic metamaterial cavity. For incident light polarized perpendicularly to the scatterer axis, critical deviations are found in low-birefringent arrangements and also with high-index cores. We demonstrate that the ability of anisotropic metallodielectric nanocavities to dramatically reduce the scattered light is associated with a multiple Fano-resonance phenomenon. We extensively explore such resonant effect to identify tunable windows of invisibility.

We show that subwavelength diffracted wave fields may be managed inside multilayered plasmonic devices to achieve ultra-resolving lensing. For that purpose we first transform both homogeneous waves and a broad band of evanescent waves into propagating Bloch modes by means of a metal/dielectric (MD) superlattice. Beam spreading is subsequently compensated by means of negative refraction in a plasmon-induced anisotropic medium that is cemented behind. A precise design of the superlens doublet may lead to nearly aberration-free images with subwavelength resolution in spite of using optical paths longer than a wavelength.

A nonsingular, polarization-dependent, 3D impulse response is derived to determine unambiguously the amplitude distribution in the image volume of a negative-refractive-index layered lens. The generalized amplitude transfer function is introduced to gain a deep insight into the resolution power of the optical element. In the near-field regime, fine details containing some depth information may be transmitted through the lens. Metamaterials with moderate absorption are appropriate for subwavelength resolution keeping a limited degree of depth discrimination.

We present a family of p-polarized optical beams that are highly localized around the optical axis and are sustained in a layered medium. This medium is comprised of a stack of thin films made of a material exhibiting negative permittivity, regularly placed in a dielectric host. We exploit the excitation of surface plasmon polaritons leading to enhanced localization near the optical axis. Also we perform an appropriate correction of the 2D wavefront in the vicinity of the beam axis for a perfect phase matching showing an optimal concentration of light.

Extreme miniaturization of on-demand optical devices such as ultrathin lenses is currently leading to significant advancements in manufacturing novel materials and nanotechnologies. Flexibility and tunability of engineered layouts enable efficient integration of complex photonic modules. In this regard, here we propose an autofocused Airy (AFA)-based metalens that operates, depending on the molded phase profile, as a multifocal focusing lens, which to the best of our knowledge has not been reported before. To do this, we call attention to the fact that the two conjugate focal points of an AFA beam can be brought into real space by applying a proper convex lens phase profile. Considering full control of the phase and amplitude of the incident light with dielectric C-shaped meta-atoms, we conceived that both generations of the AFA beam and their focusing with a convex lens could be carried out by a compact wavelength-scale metasurface. In addition, hybrid AFA focusing and phase-only lensing are demonstrated as a versatile method to be implemented in designing multifocal setups.

Though the online PDF and the print versions are correct, the web page of this paper unfortunately contained a mistake. The first author surname should read Diaz-Avino.

We present an analytical formula for the fast and accurate evaluation of nonlinear absorption in materials exhibiting an admixture of different multiphoton processes. This approach is specifically addressed for its use in thin films when the slowly varying envelope approximation applies. The contribution of absorptions of distinct order is conveniently averaged in order to use well-known expressions for a single multiphoton process. In the latter case, therefore, our simple expression is reduced toward the exact solution.

We introduce the concept of dispersive aperturing involving a beam truncation by hard-edge apertures where diameter of the processed beam changes upon frequency. Applied to focused waves, this procedure transforms power spectra at the focal point (and the surroundings). Waveforms at focus conserve pulse duration but carrier frequency may be altered substantially. In principle, some degrees of freedom allow carrier-frequency tuning at convenience.

Nonlocal effects in metal–dielectric (MD) periodic nanostructures may typically be observed when the plasmonic particles and gaps are on the scale of a few tens of nanometers, enabling under certain conditions (succinctly for epsilon near zero) a collimated beam to split into three refracted signals. We developed a method for precisely evaluating the categorized transmissivity in an air/trirefringent metamaterial interface, which uses a fast one-dimensional Fourier transform and finite element solvers of Maxwell’s equations. In periodic arrays of MD nanofilms, it is proved a tunable transmissivity switch of the multirefracted beams under varying angle of incidence and wavelength, while keeping reduced levels of reflectivity. Low-loss trirefringent nanomaterials may enable the development of ultracompact and tunable light splitters and modulators. Ministerio de Economía y Competitividad (MINECO) (TEC2013-50416-EXP).

Dyakonov-like surface waves (DSWs) propagating obliquely on an anisotropic nanostructure have been theoretically proved in a few cases including 2D photonic crystals and metal-insulator (MI) layered metamaterials. Up to now, the long-wavelength approximation has been employed in order to obtain effective parameters to be introduced in the Dyakonov equation, which is largely restricted to material inhomogeneities of a few nanometers when including metallic elements. Here, we explore DSWs propagating obliquely at the interface between an insulator and a hyperbolic metamaterial, the latter consisting of a 1D MI bandgap grating using realistic slab sizes. We found unexpected favorable conditions for the existence of such surface waves. The finite element method is used to investigate the peculiarities of this new family of DSWs. This research was funded by the Spanish Ministry of Economy and Competitiveness under the project TEC2013-50416-EXP.

Invisibility of nanotubes has recently been demonstrated in highly anisotropic metamaterials in the transition regime from hyperbolic to elliptic dispersion [Sci. Rep. 5 (2015) 16027]. In such study, the characterization of a realistic multilayered metamaterial was carried out by means of an effective medium approach providing average components of the permittivity tensor and wave fields. Here, the edge effects of the metal-dielectric stratified nanotube for different combinations were thoroughly analyzed. We show how the boundary layers, which in principle remain fully irrelevant in the estimation of the effective permittivity of the nanotube, however play a critical role in the scattering spectra and the near field patterns. A dramatic enhancement of the scattered wave field is unexpectedly experienced at the frequencies of interest when a dielectric layer is chosen to be in contact with the cavity core.