Search

Dielectric metamaterials with low ohmic losses and resonating in the local magnetic mode are preferable for enhancing material non-linearity. Here, we propose and experimentally demonstrate broadband extraordinary electromagnetic transmission (EET) behavior, which is induced by the coupling of magnetic modes of two ceramic cuboids. It is shown that extraordinary electromagnetic transmission behavior through a perforated metal sheet with a subwavelength aperture can be achieved by exciting the first-order magnetic mode Mie resonant coupling of these cuboids. Our findings indicate that the transmission bandwidth and amplitude are dependent on the strength of coupling between the two ceramic cuboids. Additionally, we utilized non-linear effects within the dielectric cuboids to achieve tunable extraordinary electromagnetic transmission behavior. Our results are promising for developing non-linearly tunable microwave devices such as filters and modulators of their strong light-matter interactions.

Superior analogs for electromagnetically induced transparency (EIT) and absorption (EIA) in metasurfaces (MSS) are universal, but fewer integrate both effects in one device, let alone contribute to polarization manipulations. Here, note that asymmetrical EITs are rigorously demonstrated under both polarization incidences in dielectric orthogonal dumbbell‐shaped structures, with a maximum group delay of 335 ps. The transverse magnetic (TM) mode excited EIT holds a transparent window at 1.318 THz close to the transverse electric (TE) mode excited that of 1.358 THz, which triggers the linear‐to‐circular polarization conversion at 1.339 THz with an optimized transmittance of 0.67, validated via the axial ratio. Additionally, asymmetrical EIAs are presented with an embedded metal‐phase VO2 plate, holding a common absorption of 0.51 at 1.340 THz, of which the insulating state affects little to the circular‐polarization output. Given the detuning of two frequencies (1.339 and 1.340 THz) can be compensated by the dispersion properties, it can be understood as the original converted circularly polarized propagating light decays with 0.5‐absorption via phase‐tuned VO2, operating as a temperature‐driven switch. The circular‐polarization transmission and absorption are integrated respectively based on EIT and EIA with the different states of VO2, promising broad prospects in multifunctional devices. [ABSTRACT FROM AUTHOR]

Abstract Since the performance of electronic circuits is becoming rather limited in face of intensively increasing of amount of information and related operations, all‐optical processing offers a promising strategy for future information system. It would benefit a great deal if the all‐optical processing could be implemented within the developed electronic chips of nanoscale structures. In that it is highly desirable to break the diffraction limit of light for achieving effective light manipulations with deep subwavelength structures compatible with the state‐of‐the‐art nanofabrication processes. It is of fundamental importance to get subwavelength optical localization, that is, squeeze light wave into subwavelength space for achieving freely manipulating of light fields. This review summarizes the development in realizing subwavelength optical localization by exciting toroidal mode in photonic metamaterials. The toroidal excitations in plasmonic metamaterials and Mie resonant metamaterials, in 3D structures and planar metamaterials, with single or few layers in spectral regime from microwave to optical frequencies are surveyed. Based on the discussion on the configurations of toroidal excitations, the recent development on toroidal‐related optical scattering control actively manipulates the toroidal excitations, and promising applications are further investigated and highlighted.

Nanostructured dielectric metamaterials have received extensive attention in the field of nanophotonics owing to their low radiative losses and coexisting electric and magnetic lattice resonance features. Unfortunately, suffering from the poor electromagnetic field localization and weak magnetic response in the typical dielectric metamaterials, it remains challenging to simultaneously realize ultra-narrow band perfect absorbance and intensified electromagnetic field resonances. Herein, we theoretically demonstrate a kind of dielectric metamaterials formed by dielectric cylindrical dimer array that supports magnetic lattice resonances. Benefiting from the collective diffraction coupling among the powerful magnetic dipole resonance in the dielectric dimer array, the proposed dielectric metamaterials synchronously manifest ultra-narrow spectral characteristics with bandwidth less than 8 nm, perfect absorbance amplitude as high as 99.7% and strong electric/magnetic field enhancement factor. The effects of the structure parameters on the optical properties of the proposed nanostructure are investigated based on numerical simulations. The linewidth of absorbance spectrum can be narrowed down to approximately 3 nm with optimal design. These excellent optical features supported by the dielectric dimer metamaterials can be explored as a high-efficiency refractive index sensor with sensitivity of 824 nm/RIU and figure of merit as high as 242 RIU−1. This work paves an exciting way for narrow band perfect absorbance and localized field enhancement, exhibiting tremendous enormous potential in biochemical sensing, surface enhanced spectroscopy, and nonlinear nanophotonics.

Dielectric metamaterials with high refractive indices may have an incredible capability to manipulate the phase, amplitude, and polarization of the incident light. Combining the high refractive index and the excellent electrical characteristics of the hybrid organic-inorganic perovskites (HOIPs), for the first time we experimentally demonstrate that metamaterial made of HOIPs can trap visible light and realize effective photon-to-electron conversion. The HOIP metamaterials are fabricated by focused ion beam milling on a solution-grown single-crystalline HOIP film. The optical absorption is significantly enhanced at the visible regime compared to that of the flat HOIP film, which originates from the excited Mie resonances and transverse cavity modes with inhibited interface reflection. Furthermore, compared to the flat film, the HOIP metamaterial shows increased photocurrent of up to ~40%, where the effective photocarrier generation efficiency increases by ~40% and the related internal efficiency by ~20%. Our data point to the potential application of HOIP metamaterials for high-efficiency light trapping and photon-to-electron conversion.

Benefited from the well-known Mie resonance, a plethora of physical phenomena and applications are attracting attention in current research on dielectric-based nanophotonics. High-index dielectric metastructures are favorable to enhance light-matter interaction in nanoscale with advantages such as low loss, optical magnetism, and multipolar responses, which are superior to their plasmonic counterpart. In this review, we highlight the important role played by Mie resonance-based multipolar and multimodal interaction in nanophotonics, introducing the concept of “multipole and multimode engineering” in artificially engineered dielectric-based metastructures and providing an overview of the recent progress of this fast-developing area. The scope of multipole and multimode engineering is restricted not only in multipolar interferences of meta-atom and meta-molecule but also in the nontrivial intermodal coupling (Fano resonance and bound states in the continuum), in the collective mode and the surface lattice mode appearing via periodic meta-lattices and aperiodic meta-assembly, in chiral enhancement via chiral and achiral dielectric metastructures, and in Mie resonance-mediated hybrid structures (Mie-plasmon and Mie-exciton). Detailed examples and the underlying physics of this area are discussed in-depth, in order to lead the multifunctional metastructures for novel applications in the future.

Chiral photonics opens new pathways to manipulate light–matter interactions and tailor the optical response of metasurfaces and ‐materials by nanostructuring nontrivial patterns. Chirality of matter, such as that of molecules, and light, which in the simplest case is given by the handedness of circular polarization, have attracted much attention for applications in chemistry, nanophotonics and optical information processing. The design of chiral photonic structures using two machine learning methods, the evolutionary algorithm, and neural network approach, for rapid and efficient optimization of optical properties for dielectric metasurfaces, is reported. The design recipes obtained for visible light in the range of transition‐metal dichalcogenide exciton resonances show a frequency‐dependent modification in the reflected light's degree of circular polarization, that is represented by the difference between left‐ and right‐circularly polarized intensity. Our results suggest the facile fabrication and characterization of optical nanopatterned reflectors for chirality‐sensitive light–matter coupling scenarios employing tungsten disulfide as possible active material with features such as valley Hall effect and optical valley coherence. [ABSTRACT FROM AUTHOR]

Since the performance of electronic circuits is becoming rather limited in face of intensively increasing of amount of information and related operations, all‐optical processing offers a promising strategy for future information system. It would benefit a great deal if the all‐optical processing could be implemented within the developed electronic chips of nanoscale structures. In that it is highly desirable to break the diffraction limit of light for achieving effective light manipulations with deep subwavelength structures compatible with the state‐of‐the‐art nanofabrication processes. It is of fundamental importance to get subwavelength optical localization, that is, squeeze light wave into subwavelength space for achieving freely manipulating of light fields. This review summarizes the development in realizing subwavelength optical localization by exciting toroidal mode in photonic metamaterials. The toroidal excitations in plasmonic metamaterials and Mie resonant metamaterials, in 3D structures and planar metamaterials, with single or few layers in spectral regime from microwave to optical frequencies are surveyed. Based on the discussion on the configurations of toroidal excitations, the recent development on toroidal‐related optical scattering control actively manipulates the toroidal excitations, and promising applications are further investigated and highlighted. [ABSTRACT FROM AUTHOR]

Dielectric metamaterials have been proved to have broad applications in the microwave and optical frequency bands. However, as the components of the communication system shrink, the coupling effects caused by tight arrangements between the dielectric structures have not been carefully studied enough yet. In this paper, the deep coupling effects in limited space between the adjacent dielectric metamaterials cubes are investigated. According to the correlation between the coupling effect and the incident wave, the influence of coupling effect on the scattering characteristics of the structure is studied from three aspects: coupling effect parallel to the wave vector/electric field/magnetic field, respectively. Field distributions and constitutive parameters are also demonstrated to illustrate the relationship between the coupling effects and scattering coefficients.

Negative refraction (NR) metamaterials are featured with unique physical properties and potential to realize full control of electromagnetic waves, which have attracted much attention since the last decade. However, few researches focus on the realization of three-dimensional dielectric NR metamaterials in optic frequency, and the current design methods need further development. In this paper, a three-dimensional all-dielectric NR metamaterial with two NR bands has been realized based on proper excitation of electric and magnetic multipoles. It is also predicted that the coupling of magnetic dipole and electric dipole can lead to the NR bands in near-infrared frequencies, and NR in the visible frequencies can be achieved by the coupling of magnetic quadrupole and electric dipole. Band structures and equal-frequency surfaces of proposed metamaterial arranged in the periodic cubic lattice are solved by adopting the plane wave expansion method, and then the results verify the existence of these two NR frequency bands in periodic metamaterials. In this way, the characteristic parameters such as transmission and absorption of light in two NR bands are also analyzed. In the meantime, the finite-deference time-domain method is used to intuitively display the phenomenon of NR and investigate the effects of disorder in particle arrangement. Besides, it is found that the proposed metamaterials have fine robustness to the disorder in particle arrangement, and these two NR bands can be tuned by adjusting volume fraction. In brief, this work provides means for preliminary designing, profound analysis and intuitively exhibition of NR metamaterials based on dielectric particles. [ABSTRACT FROM AUTHOR]

There is a fast growing interest in new applications for advanced ceramic systems in the field of functional materials and in particular for optical materials. Ceramics are entitled to fulfil the gap between glasses and single crystals in the area of photonic materials. The processing versatility and unpaired resistance to high temperature corrosive environments of some ceramics make them good candidates for such applications. However, the critical dependence of the material optical properties on microstructure makes the deep understanding of the processing conditions even more necessary than before for the fabrication of well ordered, transparent, efficient optical ceramics. This review is directed towards ceramists interested in new applications. In the paper we address some fundamental aspects of the relationship between processing, microstructure and optical properties that are illustrated with some examples related with transparent ceramics, glass ceramics, luminescence, random lasers, thermo-emissive applications, scintillators and dielectric metamaterials.

Monocrystalline titanium dioxide (TiO2) micro-spheres support two orthogonal magnetic dipole modes at terahertz (THz) frequencies due to strong dielectric anisotropy. For the first time, we experimentally detected the splitting of the first Mie mode in spheres of radii [ABSTRACT FROM AUTHOR]

• A dielectric metamaterial is theoretically proposed to simultaneously achieve ultra-narrow bandwidth and nearly perfect absorbance. • These excellent optical features can be primarily attributed to the excitation of magnetic lattice resonance mode. • The designed metamaterials can be explored as a high-efficiency refractive index sensor. Nanostructured dielectric metamaterials have received extensive attention in the field of nanophotonics owing to their low radiative losses and coexisting electric and magnetic lattice resonance features. Unfortunately, suffering from the poor electromagnetic field localization and weak magnetic response in the typical dielectric metamaterials, it remains challenging to simultaneously realize ultra-narrow band perfect absorbance and intensified electromagnetic field resonances. Herein, we theoretically demonstrate a kind of dielectric metamaterials formed by dielectric cylindrical dimer array that supports magnetic lattice resonances. Benefiting from the collective diffraction coupling among the powerful magnetic dipole resonance in the dielectric dimer array, the proposed dielectric metamaterials synchronously manifest ultra-narrow spectral characteristics with bandwidth less than 8 nm, perfect absorbance amplitude as high as 99.7% and strong electric/magnetic field enhancement factor. The effects of the structure parameters on the optical properties of the proposed nanostructure are investigated based on numerical simulations. The linewidth of absorbance spectrum can be narrowed down to approximately 3 nm with optimal design. These excellent optical features supported by the dielectric dimer metamaterials can be explored as a high-efficiency refractive index sensor with sensitivity of 824 nm/RIU and figure of merit as high as 242 RIU−1. This work paves an exciting way for narrow band perfect absorbance and localized field enhancement, exhibiting tremendous enormous potential in biochemical sensing, surface enhanced spectroscopy, and nonlinear nanophotonics. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a level set-based topology optimization method for the design of negative permeability dielectric metamaterials. Metamaterials are artificial materials that display extraordinary physical properties that are unavailable with natural materials. The aim of the formulated optimization problem is to find optimized layouts of a dielectric material that achieve negative permeability. The presence of grayscale areas in the optimized configurations critically affects the performance of metamaterials, positively as well as negatively, but configurations that contain grayscale areas are highly impractical from an engineering and manufacturing point of view. Therefore, a topology optimization method that can obtain clear optimized configurations is desirable. Here, a level set-based topology optimization method incorporating a fictitious interface energy is applied to a negative permeability dielectric metamaterial design problem. The optimization algorithm uses the Finite Element Method (FEM) for solving the equilibrium and adjoint equations, and design problems are formulated for both two- and three-dimensional cases. First, the level set-based topology optimization method is explained, and the optimization problems for the design of metamaterials are then discussed. Several optimum design examples for the design of dielectric metamaterials that demonstrate negative effective permeability at prescribed frequencies are provided to confirm the utility and validity of the presented method. [Copyright &y& Elsevier]

Based on Shore and Yaghjian's work (IEEE Trans. Antennas Propag., vol. 57, no. 10, pp. 3077–3091, Oct. 2009), a general theory has been developed to describe traveling waves on three-dimensional (3-D) periodic arrays of two sets of magnetodielectric spheres arbitrarily arranged on a simple tetragonal lattice. This theory is eventually in the form of k-\beta (dispersion) equations. To improve the computational efficiency, rapidly converging expressions and their double summation form are derived for slowly converging summations in the k-\beta equations. The dispersion diagrams of seven different arrangements of the spheres are analyzed for three combinations of sphere types: 1) dielectric spheres with equal permittivity but different radius; 2) dielectric spheres with equal radius but different permittivity; and 3) one set of spheres is purely dielectric while the other set is magnetic. Results show that the maximum bandwidths of the double-negative (DNG) region provided by different spheres arrangements for spheres combinations 1–3 are, respectively, 0.21%, 0.069%, and 7.403%. Compared to results reported in previous literature, analysis of these possible arrangements of the spheres shows similar narrow DNG bandwidths for spheres combinations 1 and 2, and wider DNG bandwidths for spheres combination 3. Although purely dielectric materials with relative permittivity much greater than one are readily available, the usefulness of purely dielectric DNG metamaterials still depends on whether the narrow bandwidths achievable are acceptable for the particular applications. Since purely magnetic materials with relative permeability much greater than one above 1 GHz are not currently available, the practicality of fabricating DNG metamaterials using arrays with spheres combination 3 is questionable for radio frequency (RF) applications, at least at present, despite the fact that this combination yields much wider DNG bandwidths than those of spheres combinations 1 and 2. [ABSTRACT FROM PUBLISHER]

Electric field intensity distribution when the distance between the cubes along magnetic field direction is different (a) 0.5 μm (b) is 2 μm. • In this study, the deep coupling effect of dense arrangement between dielectric cubes are presented. By simplifying the coupling model by coupled mode theory, the coupling effect between dielectric metamaterial cubes are quantitatively calculated by a more intuitive method. According to the correlation between the coupling effect and the incident wave, the influence of coupling effect on the scattering characteristics of the structure is studied from three aspects: coupling effect parallel to the wave vector/electric field/magnetic field, respectively. Field distributions and constitutive parameters are also demonstrated to illustrate the relationship between the coupling effects and scattering coefficients. Dielectric metamaterials have been proved to have broad applications in the microwave and optical frequency bands. However, as the components of the communication system shrink, the coupling effects caused by tight arrangements between the dielectric structures have not been carefully studied enough yet. In this paper, the deep coupling effects in limited space between the adjacent dielectric metamaterials cubes are investigated. According to the correlation between the coupling effect and the incident wave, the influence of coupling effect on the scattering characteristics of the structure is studied from three aspects: coupling effect parallel to the wave vector/electric field/magnetic field, respectively. Field distributions and constitutive parameters are also demonstrated to illustrate the relationship between the coupling effects and scattering coefficients. [ABSTRACT FROM AUTHOR]