Kerker Effect Research Articles

Resonant Metasurfaces with Van Der Waals Hyperbolic Nanoantennas and Extreme Light Confinement

This work reports on a metasurface based on optical nanoantennas made of van der Waals material hexagonal boron nitride. The optical nanoantenna made of hyperbolic material was shown to support strong localized resonant modes stemming from the propagating high-k waves in the hyperbolic material. An analytical approach was used to determine the mode profile and type of cuboid nanoantenna resonances. An electric quadrupolar mode was demonstrated to be associated with a resonant magnetic response of the nanoantenna, which resembles the induction of resonant magnetic modes in high-refractive-index nanoantennas. The analytical model accurately predicts the modes of cuboid nanoantennas due to the strong boundary reflections of the high-k waves, a capability that does not extend to plasmonic or high-refractive-index nanoantennas, where the imperfect reflection and leakage of the mode from the cavity complicate the analysis. In the reported metasurface, excitations of the multipolar resonant modes are accompanied by directional scattering and a decrease in the metasurface reflectance to zero, which is manifested as the resonant Kerker effect. Van der Waals nanoantennas are envisioned to support localized resonances and can become an important functional element of metasurfaces and transdimensional photonic components. By designing efficient subwavelength scatterers with high-quality-factor resonances, this work demonstrates that this type of nanoantenna made of naturally occurring hyperbolic material is a viable substitute for plasmonic and all-dielectric nanoantennas in developing ultra-compact photonic components.

Enhanced light confinement in nonlocal resonant metasurfaces with weak multipolar scatterers

Stronger light confinement can be enabled by nanoantennas in the nanostructure and result in efficient control of the directionality of the scattering. We report on an observation of the well-pronounced multipolar resonances from nickel nanoantennas originating from collective effects. We show that the collective coupling of multipolar modes from weak scatterers can substantially enhance the electric dipole and quadrupole resonances. We also demonstrate the generalized lattice Kerker effect in this nanoantenna array. Resonant multipolar excitations within nickel nanoantenna arrays can significantly enhance phenomena such as magneto-optical effects, indicating promising potential for advanced applications in the field of nanophotonics and sensing.

Anisotropic virtual gain and large tuning of particles’ scattering by complex-frequency excitations

Active tuning of the scattering of particles and metasurfaces is a highly sought-after property for a host of electromagnetic and photonic applications, but it normally requires challenging-to-control tunable (reconfigurable) or active (gain) media. Here, we introduce the concepts of anisotropic virtual gain and oblique Kerker effect, where a completely lossy anisotropic medium behaves exactly as its anisotropic gain counterpart upon excitation by a synthetic complex-frequency wave. The strategy allows one to largely tune the magnitude and angle of a particle’s scattering simply by changing the shape (envelope) of the incoming radiation, rather than by an involved medium-tuning mechanism. The so-attained anisotropic virtual gain enables directional super-scattering at an oblique direction with fine-management of the scattering angle. Our study is based on analytical techniques that allow multipolar decomposition of the scattered field in agreement with full-wave simulations, and lays the foundations for a light management method.

Nonlocal meta-lens with Huygens’ bound states in the continuum

Meta-lenses composed of artificial meta-atoms have stimulated substantial interest due to their compact and flexible wavefront shaping capabilities, outperforming bulk optical devices. The operating bandwidth is a critical factor determining the meta-lens’ performance across various wavelengths. Meta-lenses that operate in a narrowband manner relying on nonlocal effects can effectively reduce disturbance and crosstalk from non-resonant wavelengths, making them well-suitable for specialized applications such as nonlinear generation and augmented reality/virtual reality display. However, nonlocal meta-lenses require striking a balance between local phase manipulation and nonlocal resonance excitation, which involves trade-offs among factors like quality-factor, efficiency, manipulation dimensions, and footprint. In this work, we experimentally demonstrate the nonlocal meta-lens featuring Huygens’ bound states in the continuum (BICs) and its near-infrared imaging application. All-dielectric integrated-resonant unit is particularly optimized to efficiently induce both the quasi-BIC and generalized Kerker effect, while ensuring the rotation-angle robustness for generating geometric phase. The experimental results show that the single-layer nonlocal Huygens’ meta-lens possesses a high quality-factor of 104 and achieves a transmission polarization conversion efficiency of 55%, exceeding the theoretical limit of 25%. The wavelength-selective two-dimensional focusing and imaging are demonstrated as well. This work will pave the way for efficient nonlocal wavefront shaping and meta-devices.

InSb all-dielectric metasurface for ultrahigh efficient Si-based mid-infrared detection.

Mid-infrared (MIR) Si-based optoelectronics has wide potential applications, and its design requires simultaneous consideration of device performance optimization and the feasibility of heterogeneous integration. The emerging interest in all-dielectric metasurfaces for optoelectronic applications stems from their exceptional ability to manipulate light. In this Letter, we present our research on an InSb all-dielectric metasurface designed to achieve ultrahigh absorptivity within the 5-5.5 µm wavelength range. By integrating an InSb nanodisk array layer on a Si platform using wafer bonding and heteroepitaxial growth, we demonstrate three kinds of metasurface with high absorptivity of 98.36%, 99.28%, and 99.18%. The enhanced absorption is mainly contributed by the Kerker effect and the anapole state and the peak, with the added flexibility of tuning both the peak and bandwidth of absorption by altering the metasurface parameters. Our findings provide an alternative scheme to develop high-performance detectors and absorbers for MIR silicon photonics.

Design of Multifunctional Color Routers with Kerker Switching Using Generative Adversarial Networks

AbstractTo achieve optoelectronic devices with high resolution and efficiency, there is a pressing need for optical structural units that possess an ultrasmall footprint yet exhibit strong controllability in both the frequency and spatial domains. For dielectric nanoparticles, the overlap of electric and magnetic dipole moments can scatter light completely forward or backward, which is called Kerker theory. This effect can expand to any multipoles and any directions, re‐named as generalized Kerker effect, and realize controllable light manipulation at full space and full spectrum using well‐designed dielectric structures. However, the complex situations of multipole couplings make it difficult to achieve structural design. Here, generative artificial intelligence (AI) is utilized to facilitate multi‐objective‐oriented structural design, wherein the study leverages the concept of “combined spectra” that consider both spectra and direction ratios as labels. The proposed generative adversarial network (GAN) is named as DDGAN (double‐discriminator GAN) that discriminates both images and spectral labels. Using trained networks, the simultaneous design for scattering color and directivities, RGB color routers, as well as narrowband light routers is achieved. Notably, all generated structures possess a footprint <600 × 600 nm indicating their potential applications in optoelectronic devices with ultrahigh resolution.

ENZ medium triggered collapse of Fano resonances and emergence of generalized nonreciprocal Kerker effects by subwavelength hybrid meta-atoms

ENZ medium triggered collapse of Fano resonances and emergence of generalized nonreciprocal Kerker effects by subwavelength hybrid meta-atoms

Tunable Kerker Scattering in a Self‐Coupled Polaritonic Metasurface

AbstractThe strong coupling between electronic transitions and resonant cavity modes, facilitated by coherent energy transfer, presents unprecedented opportunities for tailoring the photoelectronic properties of constituent components. Here, the concept of Kerker effect is leveraged to demonstrate the dynamic control of scattering directionality in dielectric nanostructures by tuning the exciton‐photon coupling. First, theoretical evidence for a significant modification of the scattering directionality of a dielectric metastructure engineered by excitonic polaritons is provided. As a proof of concept, self‐coupled metasurfaces composed of bulk MoS2, which exhibit a forward/backward scattering ratio up to 20, are constructed. Importantly, tunable directionality is achieved by thermally controlling the excitonic coupling to the Mie modes. The simulated results are in good agreement with the experimental measurements, and the subsequent multipole decompositions effectively elucidate the underlying mechanism, attributed to the interplay between electric and magnetic dipole modes that are modified by excitons. The findings shed light on the control of light flow in the far field through coherent light–matter interactions, thereby opening up numerous possibilities for active optical antennas and quantum emitters on a nanoscale.

Beyond Conventional Sensing: Hybrid Plasmonic Metasurfaces and Bound States in the Continuum.

Fano resonances result from the strong coupling and interference between a broad background state and a narrow, almost discrete state, leading to the emergence of asymmetric scattering spectral profiles. Under certain conditions, Fano resonances can experience a collapse of their width due to the destructive interference of strongly coupled modes, resulting in the formation of bound states in the continuum (BIC). In such cases, the modes are simultaneously localized in the nanostructure and coexist with radiating waves, leading to an increase in the quality factor, which is virtually unlimited. In this work, we report on the design of a layered hybrid plasmonic-dielectric metasurface that facilitates strong mode coupling and the formation of BIC, resulting in resonances with a high quality factor. We demonstrate the possibility of controlling Fano resonances and tuning Rabi splitting using the nanoantenna dimensions. We also experimentally demonstrate the generalized Kerker effect in a binary arrangement of silicon nanodisks, which allows for the tuning of the collective modes and creates new photonic functionalities and improved sensing capabilities. Our findings have promising implications for developing plasmonic sensors that leverage strong light-matter interactions in hybrid metasurfaces.

Structure‐Induced Tunable Multipolar Moments and the Associated Purcell Enhancement in Silicon‐Like Metasurfaces

The recent breakthrough in integrating single quantum emitters to dielectric metasurfaces opens up avenues in quantum technologies with the possibility to obtain on‐demand single photon sources and efficient spin–photon interface. All‐dielectric metasurfaces with unprecedented possibilities of generating directional light scattering instigated a novel concept of the Kerker effect that led to applications in nanophotonics. Here, an all‐dielectric metasurface consisting of silicon‐like nanodisks with square lattice symmetry that exhibits Kerker condition governed by constructive interference of multipoles optimized for the zero‐phonon line (ZPL) of negatively charged nitrogen‐vacancy (NV‐) center at a wavelength of 640 nm is discussed. The phase and amplitude of excited multipolar moments are manipulated by varying the geometrical parameters of the metasurfaces. The constructive interference between multipolar moments generates a Kerker condition, which is tunable by varying the diameter, thickness, refractive index of nanodisks, and substrate refractive index. The Kerker condition is further used to control the emission from a single NV‐ center and a Purcell enhancement of 300 times is achieved at 640 nm. The study profoundly explores new insights into quantum metasurfaces and paves a new way to utilize dielectric resonators with emitters as on‐chip quantum light sources at Kerker condition.

Special scattering regimes for conical all-dielectric nanoparticles

All-dielectric nanophotonics opens a venue for a variety of novel phenomena and scattering regimes driven by unique optical effects in semiconductor and dielectric nanoresonators. Their peculiar optical signatures enabled by simultaneous electric and magnetic responses in the visible range pave a way for a plenty of new applications in nano-optics, biology, sensing, etc. In this work, we investigate fabrication-friendly truncated cone resonators and achieve several important scattering regimes due to the inherent property of cones—broken symmetry along the main axis without involving complex geometries or structured beams. We show this symmetry breaking to deliver various kinds of Kerker effects (generalized and transverse Kerker effects), non-scattering hybrid anapole regime (simultaneous anapole conditions for all the multipoles in a particle leading to the nearly full scattering suppression) and, vice versa, superscattering regime. Being governed by the same straightforward geometrical paradigm, discussed effects could greatly simplify the manufacturing process of photonic devices with different functionalities. Moreover, the additional degrees of freedom driven by the conicity open new horizons to tailor light-matter interactions at the nanoscale.

Polarization-controlled dual resonant lattice Kerker effects

Polarization-controlled dual resonant lattice Kerker effects

Dynamic Tuning and Swapping of Electric and Magnetic Dipolar Mie Resonances in High Index Dielectric Particles Dispersed in an Anisotropic Medium

AbstractHigh refractive index (n > 2.5) dielectric particles support strong electric and magnetic Mie resonances in the visible region enabling optical properties such as directional scattering, anapole modes, and Fano resonances with applications in nanophotonics. Selenium particles, which possess a high refractive index at optical frequencies, have been synthesized using a controlled approach involving a moderate reduction of selenious acid to obtain particles of the desired size. The extinction spectra from UV–vis spectroscopy in conjunction with theoretical simulations confirm the presence of highly size‐dependent dipole and quadrupole Mie resonances in the visible region. Dynamic tuning of magnetic and electric Mie resonances and swapping of electric and magnetic dipoles are observed in a colloidal dispersion of 250 nm‐sized selenium particles in a nematic liquid crystal due to the anisotropic nature of the latter. Theoretical simulations reveal the presence of unidirectional scattering and photonic‐nanojet formation, attributed to generalized Kerker's effects in nanophotonics and meta‐optics, due to the swapping phenomena leading to the superposition of dipole and quadrupole resonances. The manipulation of Mie resonances in the liquid crystal based colloidal metamaterial has the potential for large‐scale and cost‐effective nanophotonic device applications.

Kerker Effects and Bound States in the Continuum in PT-Symmetric Dielectric Metasurfaces

We investigate the light transmission and reflection spectra of parity-time (PT) symmetric dielectric metasurfaces composed of high refractive index nanostructures with in-plane gain-loss modulation through the scattering matrix and semianalytical Cartesian multipoles methods. We find that the Kerker effects, i.e., the strong forward-to-backward asymmetric scattering originating from overlapping the electric and magnetic multipolar resonances, can be tailored by the gain and loss. In addition, we observe another kind of high-Q resonances, i.e., quasi-bound states in the continuum which couple to the electric and magnetic multipolar radiations, in the transmission and reflection spectra with different incident polarizations lights by manipulating the gain and loss in the metasurfaces. Our results suggest the ways to achieve Kerker effects and engineer the resonances in non-Hermitian metasurfaces for many practical applications in nanophotonics.

Polarization-independent resonant lattice Kerker effect in phase-change metasurface

Resonant lattice Kerker effect in periodic resonators is one of the most interesting generalizations of the Kerker effect that relates to various fascinating functionalities such as scattering management and Huygens metasurfaces. However, so far this effect has been shown to be sensitive to the incident polarization, restricting its applications. Here, we report, for the first time, polarization-independent resonant lattice Kerker effect in metasurfaces composed of periodic Ge2Se2Te5 (GST) disks. For such a metasurface of square lattice, the spectrally overlap of the electric dipole and magnetic dipole surface lattice resonances can be realized by choosing an appropriate GST crystalline fraction regardless of the incident polarization. The operation wavelength and the required GST crystalline fraction can be conveniently tuned over large ranges since these parameters scale linearly with the disk size and the lattice period, greatly facilitating the design. Making use of the obtained resonant lattice Kerker effect, we realize a reconfigurable and polarization-independent lattice Huygens’ metasurface with a dynamic phase modulation of close to 2π and high transmittance. This work will advance the engineering of the resonant lattice Kerker effect and promote its applications in phase modulation and wavefront control.

Transverse Kerker effect in all-dielectric spheroidal particles

Kerker effect is one of the unique phenomena in modern electrodynamics. Due to overlapping of electric and magnetic dipole moments, all-dielectric particles can be invisible in forward or backward directions. In our paper we propose new conditions between resonantly excited electric dipole and magnetic quadrupole in ceramic high index spheroidal particles for demonstrating transverse Kerker effect. Moreover, we perform proof-of-concept microwave experiment and demonstrate dumbbell radiation pattern with suppressed scattering in both forward and backward directions and enhanced scattering in lateral directions. Our concept is promising for future planar lasers, nonreflected metasurface and laterally excited waveguides and nanoantennas.

Transverse Kerker Effect for Dipole Sources.

Transverse Kerker effect is known by the directional scattering of an electromagnetic plane wave perpendicular to the propagation direction with nearly suppression of both forward and backward scattering. Compared with plane waves, localized electromagnetic emitters are more general sources in modern nanophotonics. As a typical example, manipulating the emission direction of a quantum dot is of vital importance for the investigation of on-chip quantum optics and quantum information processing. Herein, we introduce the concept of transverse Kerker effect for dipole sources utilizing a subwavelength dielectric antenna, where the radiative power of magnetic, electric, and more general chiral dipole emitters can be dominantly redirected along their dipole moments with nearly suppression of radiation perpendicular to the dipole moments. This type of transverse Kerker effect is also associated with Purcell enhancement mediated by electromagnetic multipolar resonances induced in the dielectric antenna. Analytical conditions of transverse Kerker effect are derived for the magnetic, electric, and chiral dipole emitters. We further provide microwave experiment validation for the magnetic dipole emitter. Our results provide new physical mechanisms to manipulate the emission properties of localized electromagnetic source which might facilitate the on-chip quantum optics and beyond.

Realization of ultrawide-angle high transmission and its applications in 5G millimeter-wave communications.

By using single-layer metasurfaces, we realized ultrawide-angle high-transmission in the millimeter-wave band, which allowed more than 98% transmission of dual-polarized electromagnetic waves for almost all incident angles. The multipolar expansion method was used to analyze and verify the condition of the generalized Kerker effect at the corresponding reflected angles. Using quartz glass substrates with the same metallic periodic structures, electromagnetic windows are proposed that can improve any-directed 5G millimeter-wave communication signals from outdoor to indoor environments. The proposed interpretations can connect the Kerker effect with actual applications and enable the design of easy-to-integrate all-angle Kerker effect metasurface devices.

Germanium Metasurfaces with Lattice Kerker Effect in Near-Infrared Photodetectors.

In O-and C-band optical communications, Ge is a promising material for detecting optical signals that are encoded into electrical signals. Herein, we study 2D periodic Ge metasurfaces that support optically induced electric dipole and magnetic dipole lattice resonances. By overlapping Mie resonances and electric dipole lattice resonances, we realize the resonant lattice Kerker effect and achieve narrowband absorption. This effect was applied to the photodetector demonstrated in this study. The absorptance of the Ge nanoantenna arrays increased 6-fold compared to that of the unpatterned Ge films. In addition, the photocurrent in such Ge metasurface photodetectors increases by approximately 5 times compared with that in plane Ge film photodetectors by the interaction of these strong near-fields with semiconductors and the further transformation of the optical energy into electricity.

Template‐Assisted Self‐Assembly of Colloidal Silicon Nanoparticles for All‐Dielectric Nanoantenna

AbstractA solution‐based bottom‐up process to produce one‐ and two‐dimensional arrays of densely packed spherical nanoparticles (NPs) of crystalline silicon (Si), having the lowest order Mie resonance in the visible range, is developed. First, an agglomeration‐free solution of Si NPs with a narrow size distribution is prepared. By using grooves fabricated on the surface of a polymer as a template, arrays of Si NPs with different shapes are formed by a template‐assisted self‐assembly method, and then they are transferred to an arbitrary substrate. To demonstrate proper formation of Si NP arrays, polarization‐resolved scattering spectra are measured for different size linear arrays, i.e., a monomer to a pentamer, of Si NPs placed on a silica substrate. The observed spectra are well‐reproduced by the numerical simulations. When the polarization direction of incident light is parallel to the array axis, the scattering spectra are strongly modified from that of a Si NP monomer due to near‐field coupling of the electric dipole (ED) modes. In a Si NP tetramer, the peak of the ED mode overlaps with that of the magnetic dipole (MD) mode and strong forward scattering is observed at the MD peak wavelength due to the Kerker effect.