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In this article, a transmissive three-frequency linearly polarized (LP) wave to circularly polarized (CP) wave metasurface is designed using all-dielectric materials. The structure is composed of a cross-shaped bar resonator and a split circular ring resonator. Numerical simulations results show that when the LP wave is incident on the device, it will be converted into nearly perfect right-handed circularly polarized (RHCP), left-handed circularly polarized and RHCP waves at 2.2146, 2.2467 and 2.3144 THz. The distribution of the conduct current, electric field and magnetic field are investigated to explain the physical mechanism. And the influence of the structural parameters and different incident angles for the structure are also studied in the end. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Nanchang University (Engineering & Technology) is the property of Nanchang University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

All-silicon terahertz absorbers have attracted considerable interest. We present a design and numerical study of an all-silicon polarization-insensitive terahertz metamaterial absorber. The meta-atoms of the metamaterial absorber are square silicon rings which can be viewed as gratings. By properly optimizing the structure of the meta-atom, we achieve a broadband absorptivity that is above 90% ranging from 0.77 THz to 2.53 THz, with a relative bandwidth of 106.7%. Impedance matching reduces the reflection of the terahertz waves and the (0, ±1)-order diffraction induce the strong absorption. The absorption of this absorber is insensitive to the polarization of the terahertz wave and has a large incident angle tolerance of up to 60 degrees. The all-silicon metamaterial absorber proposed here provides an effective way to obtain broadband absorption in the terahertz regime. Metamaterial absorbers have outstanding applications in terahertz communication and imaging. [ABSTRACT FROM AUTHOR]

A novel, all-dielectric metasurface, featuring a missing wedge-shaped nanodisk, is proposed to investigate optical characteristics. By introducing symmetry-breaking to induce Fano resonance, the metasurface achieves an impressive Q-factor of 1202 in the near-infrared spectrum, with a remarkably narrow full width at half maximum (FWHM) of less than 1 nm. The ability to adjust the wavelength resonance by manipulating the structure of the wedge-shaped nanodisk offers a simple and efficient approach for metasurface design. This breakthrough holds great potential for various applications in sensing and optical filtering, marking a significant advancement in the field of nanophotonics. [ABSTRACT FROM AUTHOR]

An all-dielectric hollow nanocylinder dimer metastructure with high sensitivity is proposed and investigated. The unit structure consists of two nanocylinders with two circular air holes etched into them, which are periodically aligned on the SiO2 substrate. Combined with the bound states in the continuum (BIC) theory, five Fano resonances are achieved by breaking the symmetry (height symmetry or aperture symmetry) of two hollow nanocylinders. The modulation depth can reach nearly 100%, the maximum Q-factor exceeds 2220, the refractive index sensitivity is 870 nm/RIU, and the figure of merit (FOM) of 600 is achieved. Therefore, it is believed that the suggested metastructure can be widely used in lasers, optical switches and biological sensors due to its high sensitivity and high Q-factor. [ABSTRACT FROM AUTHOR]

In this paper, a structurally simple transmissive all-dielectric metamaterial absorber is designed, fabricated and measured. The unit cell consists of photosensitive resin and water, which the water layers composed of rectangle loop, rectangular block and traffic circle. It achieves over 90% absorption of electromagnetic waves in the frequency range between 11.0 and 27.3 GHz. Meanwhile, three absorption peaks are located at 12.5, 18.4, and 26.0 GHz, which the absorptive are 97.4%, 98.3%, and 98.5%, respectively. In addition, the characteristics of the designed metamaterial reveal wide-incident angle absorption and polarization-insensitive properties. The experimental sample is measured by using the free-space method, and the experimental results are verified to be in well agreement with the simulation data. Observing the distribution of electric and magnetic fields at different resonance frequencies, the physical mechanism of the absorption is attributed to strong magnetic resonance. Therefore, the proposed metamaterial has potential for widespread use in the fields of civilian and military. [ABSTRACT FROM AUTHOR]

A novel asymmetric all-dielectric metasurface supporting multiple Fano resonances with high quality-factor through the excitation of quasi-bound states in the continuum is theoretically investigated. It is demonstrated that two resonances in the near-infrared wavelength are excited by the symmetry-protected bound state in the continuum, which can be transformed into the electric dipole and the toroidal dipole quasi-BIC resonance with high quality-factor by breaking the symmetry of metasurface. Moreover, the sensing properties based on different liquid refractive indexes are researched theoretically. The results show that the maximum quality-factor of the Fano resonance peak is 8422, and the sensitivity can reach 402 nm/RIU, with a maximum figure of merit of 2400 RIU−1. This research is believed to further promote the development of optical sensing and nonlinear optics. [ABSTRACT FROM AUTHOR]

A transmission‐type all‐medium element is proposed to construct a coded metasurface. Due to the single‐layer metasurface unit structure, large reflection loss will be caused when the base plane is incident. In order to improve the efficiency of the coded metasurface device and reduce the reflection loss, the authors propose a double‐sided metasurface digital unit structure and introduces a wideband anti‐reflection pyramid microstructure to achieve significantly improved transmission characteristics. The optimized unit structure is coded and the coded metasurface is constructed. Different coding metasurface sequences are constructed based on 1‐bit, 2‐bit, and 3‐bit digital coding units. According to generalized Snell's law, the number of transmitted beams can be controlled. The authors introduce complex code addition theory to construct multifunctional beam control metasurface. Based on the far field scattering theory of metasurface, the addition theory of different sequences of transmission‐coded metasurface is analyzed. The addition operation of the superposition of two sets of symmetric double beams and two sets of ordinary double beams can be realized. Based on the analysis of far‐field scattering characteristics, the multifunctional coded metasurface is demonstrated, that is, multiple functions are simultaneously superimposed in one array without interference. [ABSTRACT FROM AUTHOR]

We demonstrate a simple subwavelength all-dielectric photonic device with greatly enhanced transverse magneto-optical Kerr effect (TMOKE) in the transmission mode. The concept utilizes the diffracted waves of the periodic magnetic material bismuth-substituted iron garnet grating to excite the guided mode in the planar waveguide, and adds a buffer layer under the all-dielectric guided mode grating. In the study, it was found that increasing the refractive index of the buffer layer can reduce the coupling between the grating and the waveguide, so that full width at half maximum of the transmission spectra can be narrowed, and the value of TMOKE can be greatly enhanced up to 1.82. It is worth noting that the TMOKE value of the guide mode grating with buffer layer is 3 times that of those without buffer layer, thus opening up different avenues for designing efficient, integrated and low-loss magneto-optical devices. Enhanced TMOKE has great potential for applications such as biosensing/high-resolution sensing, magneto-optical modulation and magnetic measurement.

Chiral metasurfaces have great potential in various applications such as polarimetric imaging and biomedical recognition. However, simultaneous broadband and high circular dichroism (CD) with high polarization extinction ratio (PER) remains a challenge. Here, we present a novel approach to realize simultaneous broadband and high CD with high PER in the optical communication band using a two-dimensional all-dielectric chiral metasurface. The structure is formed by a two-level chiral structure of split cross (first-order) and trapezoid-shaped (second-order) of Si nano ribs, respectively, in which constructively coupled first- and second-order of chirality occurs, resulting in the broad chiral response in the far field of multipoles excited by incident light of different chiralities. Theoretical results show that a CD in transmission reaching 0.9 (up to 0.993) and a PER exceeding 20 dB (up to 35 dB) over the entire wavelength range from 1.39 to 1.61 μm can be achieved simultaneously, consistent with the experimental results of CD ∼0.9 and PER of 10 dB (up to 19.7 dB). Our design paves the way for chiral metasurfaces toward practical applications in terms of working bandwidth, high CD and PER as well as integrality of the devices in many fields.

A novel, all-dielectric metasurface, featuring a missing wedge-shaped nanodisk, is proposed to investigate optical characteristics. By introducing symmetry-breaking to induce Fano resonance, the metasurface achieves an impressive Q-factor of 1202 in the near-infrared spectrum, with a remarkably narrow full width at half maximum (FWHM) of less than 1 nm. The ability to adjust the wavelength resonance by manipulating the structure of the wedge-shaped nanodisk offers a simple and efficient approach for metasurface design. This breakthrough holds great potential for various applications in sensing and optical filtering, marking a significant advancement in the field of nanophotonics.

Metasurface tuning is performed using different ways for a wide range of applications. This study presents the design of a thermally‐tuned all‐dielectric reconfigurable metasurface. A microfluidic channel, filled with different concentrations of tellurium–selenium (Te‐Se) alloy, is added on the top of the elliptical dielectric resonator (EDR) unit cell of the considered metasurface. The electrical properties of used semiconductor alloy are varied in the range of 400 to 700°C (steps size of 100°C). The impact of thermal tuning on the reflection and transmission characteristics of the designed metasurface is analyzed in the frequency range of 20–30 GHz using COMSOL Multiphysics. Obtained results demonstrated that the realized metasurface exhibits reconfigurable behavior in terms of variations in the reflection and transmission characteristics with a change in either temperature or concentrations of selenium and tellurium. The wider bands with high reflection and low transmission frequency bands are obtained with lower concentrations of selenium and tellurium for all operating temperatures. [ABSTRACT FROM AUTHOR]

All-silicon terahertz absorbers have attracted considerable interest. We present a design and numerical study of an all-silicon polarization-insensitive terahertz metamaterial absorber. The meta-atoms of the metamaterial absorber are square silicon rings which can be viewed as gratings. By properly optimizing the structure of the meta-atom, we achieve a broadband absorptivity that is above 90% ranging from 0.77 THz to 2.53 THz, with a relative bandwidth of 106.7%. Impedance matching reduces the reflection of the terahertz waves and the (0, ±1)-order diffraction induce the strong absorption. The absorption of this absorber is insensitive to the polarization of the terahertz wave and has a large incident angle tolerance of up to 60 degrees. The all-silicon metamaterial absorber proposed here provides an effective way to obtain broadband absorption in the terahertz regime. Metamaterial absorbers have outstanding applications in terahertz communication and imaging.

Abstract Metasurface tuning is performed using different ways for a wide range of applications. This study presents the design of a thermally‐tuned all‐dielectric reconfigurable metasurface. A microfluidic channel, filled with different concentrations of tellurium–selenium (Te‐Se) alloy, is added on the top of the elliptical dielectric resonator (EDR) unit cell of the considered metasurface. The electrical properties of used semiconductor alloy are varied in the range of 400 to 700°C (steps size of 100°C). The impact of thermal tuning on the reflection and transmission characteristics of the designed metasurface is analyzed in the frequency range of 20–30 GHz using COMSOL Multiphysics. Obtained results demonstrated that the realized metasurface exhibits reconfigurable behavior in terms of variations in the reflection and transmission characteristics with a change in either temperature or concentrations of selenium and tellurium. The wider bands with high reflection and low transmission frequency bands are obtained with lower concentrations of selenium and tellurium for all operating temperatures.

In this article, an all-dielectric metasurface-based refractive index sensor is proposed in the near-infrared wavelength regime. The sensor employs well known magnetic dipole and electric dipole resonances for sensing. We have also computationally demonstrated that sensitivity and figure of merit of the sensor can be enhanced by increasing the interaction between the electromagnetic field and the surrounding medium using a suitable design modification. The proposed improved sensor can be used in anemia detection and also to measure its progress as proposed in this work. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As a type of material engineered to serve special purposes, metamaterials have attracted more attention from researchers. The traditional metamaterial absorber usually has a sandwich structure: periodic metal patches on the top surface, intermediate dielectric lay in between, and a metal layer on the bottom. The top metal must be designed with extra accuracy and complexity to obtain a stronger wave absorption effect and multi-band wave absorption ability, which undoubtedly increases the difficulty and cost of design and fabrication. To overcome the inherent problems of a metal structure, the absorber based on all-dielectric metamaterial is proposed. Combining 3D printing technology with the principle of electromagnetic metamaterial, a multi-band metamaterial absorber is proposed using 3D printed materials. In this paper, we designed the metamaterial absorber with acrylonitrile butadiene styrene, which has many advantages: lightweight, small volume, saline-alkaline tolerance, low cost, and easy to fabricate. Because there is no metal resonance surface structure, the absorber has the property of lightweight, small volume, and easy to prepare. We also tested the resonance absorption of this 3D printed absorber and the results showed that resonance absorption peaks below − 10 dB can be realized and the minimum peak can reach − 35 dB. [ABSTRACT FROM AUTHOR]

In this paper, an all-dielectric metastructure-based high-contrast refractive index sensor is proposed. This structure can be utilized to detect various concentrations of glycerol-water mixtures by evaluating transmission spectral lines and resonant wavelength shifts related with liquid concentration detection. The experimental and calculated results of the developed sensor structure are able to excite three resonance peaks, demonstrating that the structure is capable of reaching excellent sensing capabilities. It has been established that this work has the potential to be useful in medical and biological detection; this is of great scientific and practical significance. [ABSTRACT FROM AUTHOR]

All-dielectric metasurfaces have great potential as highly sensitive refractometric sensors relying on their spectral shifts because of an extensive range of design flexibilities and their smaller absorption losses than plasmonic platforms. However, simultaneously realizing both high quality (Q) factors and the large interplay of light with external medium in such photonic sensors remains one of the key challenges for their better performance. This study proposes silicon block metasurfaces with nanogaps to overcome this challenge based on quasi-bound states in the continuum (BICs). We show that the metasurface has two quasi-BIC modes—magnetic dipole (MD) and electric quadrupole (EQ)—and their electric fields experience large enhancement at the ∼30 nm nanogap regions. Consequently, introducing nanogaps into the metasurfaces increases the environmental refractive index sensitivity by up to 2.7 times in the MD mode while keeping the high Q factors and achieves the figure-of-merit (FOM) of 239. In addition, we show that the appropriate selection of the amount of asymmetry is needed under the trade-off between the FOM and spectral signal-to-noise ratio, which provides design guidelines for highly sensitive biosensors based on quasi-BICs.

Beam splitters are widely applied in various optical systems as a common beam-splitting device. The conventional stereoscopic and flat-type beam splitters greatly limit the packaging and integration of optical systems due to their large size and restricted emitting direction. Recently, beam-splitting devices made of various transmissive or reflective metasurfaces have shown the potential to overcome these challenges. However, in optical systems such as machine vision, these single-ended beam splitters increase the design complexity of the signal feedback link due to the limitation of the beam-splitting path direction. Here, we proposed and numerically simulated a transflective all-dielectric metasurface beam splitter by applying incompletely transmissive structural designs to the metasurface and using the transmission phase modulation mechanism. It can realize the beam separation for arbitrarily polarized incident light on the same side of the normal at both transmissive and reflective ends with a single-layer unit cell arrangement structure and has a similar emergence angle. The results reveal that at 1550 nm, the angular tolerance bandwidth is about 32°, the total splitting efficiency is over 90%, and the splitting ratio is approximately 1:1. After comparison and verification of simulation results, this transflective metasurface beam splitter is hopeful to be applied in new compact optical systems that require real-time signal feedback, such as coaxial light sources and photoelectric sensing. [ABSTRACT FROM AUTHOR]

Although many multi-band terahertz (THz)–metasurface perfect absorbers (MPAs) have been proposed, many efforts are still suffering from complex structure design and high fabrication cost, thus limited in practical application. Here, a simple design of the dual-band MPA was proposed in the THz region, which is composed of the complementary-star-shaped (CSS) structure all-dielectric GaAs array. Simulation results show that the designed MPA can achieve an absorbance of over 99.9% at 0.715 THz and 0.861 THz, respectively, which can be confirmed by the coupling mode theory (CMT). In addition, the high Q-factors of about 79.58 and 78.27 of the designed MPA can be achieved, respectively. The observed perfect absorption of the MPA is mainly contributed to the excitations of the surface plasmonic polaritons (SPPs) modes. The absorption properties of the MPA can be adjusted by varying the geometric parameters of the unit-cell structure. Due to its excellent properties, the designed dual-band MPA may find many potential THz applications in sensing, detecting, thermal emitting, and imaging. [ABSTRACT FROM AUTHOR]

A novel asymmetric all-dielectric metasurface supporting multiple Fano resonances with high quality-factor through the excitation of quasi-bound states in the continuum is theoretically investigated. It is demonstrated that two resonances in the near-infrared wavelength are excited by the symmetry-protected bound state in the continuum, which can be transformed into the electric dipole and the toroidal dipole quasi-BIC resonance with high quality-factor by breaking the symmetry of metasurface. Moreover, the sensing properties based on different liquid refractive indexes are researched theoretically. The results show that the maximum quality-factor of the Fano resonance peak is 8422, and the sensitivity can reach 402 nm/RIU, with a maximum figure of merit of 2400 RIU−1. This research is believed to further promote the development of optical sensing and nonlinear optics.

In this study, an all-dielectric metamaterial absorber consisting of a ring nanocavity array, a spacer layer, and a metallic substrate is designed and investigated. The simulation results show that the two perfect absorption peaks (99.91% and 99.96%) are achieved at 539 nm and 673 nm. The two resonance modes caused by the different electric and magnetic field distributions of the ring nanocavity structure lead to different absorption and sensing properties. In addition, the influence of the structural parameters, such as the width of the nanocavity, on the sensing characteristics was studied and is presented here. A high sensitivity and narrow band result in a huge figure of merit when the proposed absorber is operated as a refractive index sensor. [ABSTRACT FROM AUTHOR]

Water-based absorbers have shown great development potential in the past few years. In this paper, an all-dielectric transparent bi-directional water-based broadband metamaterial absorber is designed. The simulation results indicate that absorptance of the absorber is over 90% in 5.7–41.6 GHz, and its fraction bandwidth is 151.8%. The experimental results are greatly consistent with the simulations. The designed absorber has excellent performances of polarization insensitivity, oblique incidence stability and thermal stability. When the absorptance is more than 0.8, the maximum incident angle reaches 40° in TE mode and is over 60° in TM mode. In 0–80 °C, absorptance of the absorber is hardly changed. Because of the optical transparency of the designed absorber, it can be extensively used in stealth window weapons and electromagnetic compatibility equipment. [ABSTRACT FROM AUTHOR]

We numerically investigated double symmetry-protected bound states in the continuum (BICs) in an all-dielectric metasurface composed of a periodically arranged silicon disk etched with a rectangular slot. Quality factors of the double BICs promptly increase with the decrease of the asymmetry parameter, and their electric fields are locally enhanced in surrounding medium. The refractive index sensor based on the double BICs exhibits excellent performance with figures of merit of 3243 and 171,965, respectively. Our proposed metasurface will open up avenues for the development of applications in multiwavelength sensors, narrow-band filters, optical switches, and nonlinear optics. [ABSTRACT FROM AUTHOR]

Based on the generalized Snell's law, an achromatic cloaking device with oblique incidence based on multilayer frame metasurfaces is proposed. The cloaking device consists of three layers of metasurface structures, which have functions of beam deflection, steering, and collection, respectively. To solve the problems of ohmic loss and high temperature resistance of metal structure, all-silicon dielectric material is used to design the metasurface unit structures. The linear dispersion and phase gradient of the unit structures can be controlled simultaneously by changing the dimension parameters of the all-silicon dielectric unit structures, so that the electromagnetic waves with different frequencies of oblique incidence can deflect around the cloaking object without scattering. At the frequencies of 0.375 and 0.75 THz, the simulation results show that the designed device can achieve the function of oblique incidence achromatic cloaking, and reduce the influence of chromatic dispersion on the metasurface cloaking device. The structures and methods used in this paper not only enrich the functions and types of metasurface devices, but also lay a foundation for the development of achromatic cloaking metasurface, which has a certain development prospect in radar, hallucinatory optics, perfect lens, and other fields. [ABSTRACT FROM AUTHOR]

A temperature‐tunable terahertz (THz) perfect absorber (PA) composed of a periodic array of deep subwavelength micro‐cross‐shaped (MCS) structures of the strontium titanate (STO) resonator is proposed and investigated theoretically, which can be applicable for the temperature sensing. Simulation results indicate that the absorbance of 99.8% at 0.221 THz can be achieved when the designed PA is under the room temperature of T = 300 K, which is in good agreement with the calculation done by the coupling mode theory (CMT). The simulated distributions of electric and magnetic fields in the unit‐cell structure of the designed PA reveal that the observed perfect absorption is mainly attributed to the Mie resonance of the all‐dielectric MCS structure STO. In addition, this designed PA is polarization‐insensitive and wide‐angle absorption for both transverse magnetic (TM) and transverse electric (TE) waves. The resonance absorption properties of the designed PA can be controlled by changing the geometrical parameters of STO resonator structure. The designed PA can be served as a temperature sensor, which has a sensitivity of about 0.37 GHz K−1 since the electrical property of the STO is dependent on the variation of surrounding temperature. Furthermore, the perfect absorption can also be achieved by the PAs using the square, circular, and ring STO structures. The proposed design concepts of the STO‐based tunable PAs can find potential THz applications in sensing, detecting, imaging, and so on. [ABSTRACT FROM AUTHOR]

• A three-layer all-dielectric structure achieves dynamic tunable structural color. • The structure suppresses multimodal spectra, enhancing transmission rates for primary CMY colors. • The transmission efficiency for magenta reaches 96 %, yellow 89 %, and cyan an outstanding 99 %. In this paper, we propose a three-layer all-dielectric structure capable of dynamic tunability by varying the lattice period and incident angle, thereby facilitating the production of high-quality colors. By integrating three dielectric layers with outer rings and inner cylinders, we effectively suppress multimodal spectra, leading to significantly improved transmission rates for the CMY primary colors. The high transmission efficiency for magenta reaches 96 %, yellow reaches 89 %, and cyan attains an outstanding 99 %. The materials utilized in this design possess characteristics conducive to practical fabrication, thereby offering extensive possibilities for practical applications. Furthermore, our findings provide new insights and potential avenues for future research and applications of structural colors in all-dielectric materials. [ABSTRACT FROM AUTHOR]

We have designed and analyzed the high quality-factor (Q-factor), multiple Fano resonances device on the basis of the all-dielectric metastructure. The unit structure consists of two rectangular air holes etched within a silicon cube and periodically aligns on the substrate of silicon dioxide. The results demonstrate that four Fano resonances are achieved by integrating the theory of bound states in the continuum (BIC)and breaking the symmetry (width symmetry or depth symmetry) of two rectangle air holes, and the resonant wavelength can be modified by altering structural parameters. The sensing characteristics of the presented structure are studied. The sensitivity(S) of 304 nm/RIU, the maximal Q-factor of 2142 and the figure of merit (FOM) of 515.3 are achieved while width symmetry is broken. Meanwhile, the sensitivity of 280 nm/RIU, the maximal Q-factor of 2517 and the FOM of 560 are gotted through breaking depth symmetry. The proposed metastructures can be used for the lasers, biosensing and nonlinear optics.

Reconfigurable metasurfaces provide a new way for applications requiring dynamic tunability, such as focusing lenses, holographic displays, optical switch and so on. In this paper, a reconfigurable bi-functional metasurface is proposed. Using phase-change material Ge2Sb2Se4Te1(GSST) as pattern layer, calcium fluoride as substrate, the metasurface can be switched from highly transmission (90 %) mode to perfect absorption (99 %) mode in the 1.55 μm wavelength region, when the GSST layer is transformed from the amorphous to crystalline state. And the response of this metasurface is independent of the polarization of incident wave. Our novel design has potential significance in the design of infrared switching devices in the future.

Due to their extraordinary abilities to manipulate light propagation at the nanoscale, dielectric resonators that generate electric and magnetic Mie resonances for minimal optical loss have recently attracted great interest. Based on an all-dielectric metasurface, made of H-type silicon nanoarrays, this study proposed and constructed a visible-wavelength-range color filter, with high-quality Mie resonance and the ability to synthesize new colors. Using the finite-difference time-domain (FDTD) approach, we can create a larger color gamut by modifying the H-type array's structural properties. The all-dielectric color filter suggested has a high color saturation and narrow bandwidth. The Mie resonance can be adjusted by manipulating the structural characteristics. By translating the reflectance spectrum into color coordinates and using the CIE1931 chromaticity diagram, a wide range of colors can be generated. This color filter offers a larger color range and saturation than other color filters. We produced color passband filters that span the visible spectrum using Mie resonator arrays, based on an H-type nanoresonator. This technology could have many applications, including high-resolution color printing, color-tunable switches, and sensing systems. [ABSTRACT FROM AUTHOR]

All-dielectric magnetophotonic nanostructures are promising for integrated nanophotonic devices with high resolution and sensitivity, but their design requires computationally demanding electromagnetic simulations evaluated through trial and error. In this paper, we propose a machine-learning approach to accelerate the design of these nanostructures. Using a data set of 12 170 samples containing four geometric parameters of the nanostructure and the incidence wavelength, trained neural network and polynomial regression algorithms were capable of predicting the amplitude of the transverse magneto-optical Kerr effect (TMOKE) within a time frame of 10 -3 s and mean square error below 4.2%. With this approach, one can readily identify nanostructures suitable for sensing at ultralow analyte concentrations in aqueous solutions. As a proof of principle, we used the machine-learning models to determine the sensitivity ( S = |Δθ res /Δ n a |) of a nanophotonic grating, which is competitive with state-of-the-art systems and exhibits a figure of merit of 672 RIU -1 . Furthermore, researchers can use the predictions of TMOKE peaks generated by the algorithms to assess the suitability for experimental setups, adding a layer of utility to the machine-learning methodology.

Abstract We propose and numerically demonstrate a phase-gradient metasurface with high anomalous transmission efficiency and a large anomalous refraction angle that consists of discontinuous regular hexagonal nanorods supported by a silica substrate. The metasurface achieves high anomalous transmission efficiency and a full 2 $$\pi$$ π phase shift for the wavelength range of 1400–1600 nm. At a central wavelength of approximately 1529 nm, the total transmission efficiency reaches 96.5%, and the desired anomalous transmission efficiency reaches 96.2%, with an anomalous refraction angle as large as 30.64. With the adjustment of the period and the number of nanorods per periodic interval, the anomalous transmission efficiency exceeds 69.6% for a large anomalous refraction angle of 68.58. The superior performance of the proposed design may pave the way for its application in optical wavefront control devices.

All-dielectric metasurfaces supporting photonic bound states in the continuum (BICs) are an exciting toolkit for achieving resonances with ultranarrow linewidths. However, the transition from theory to experimental realization can significantly reduce the optical performance of BIC-based nanophotonic systems, severely limiting their application potential. Here, we introduce a combined numerical/experimental methodology for predicting how unavoidable tolerances in nanofabrication such as random geometrical variations affect the performance of different BIC metasurface designs. We compare several established all-dielectric BIC unit cell geometries with broken in-plane inversion symmetry including tilted ellipses, asymmetric double rods, and split rings. Significantly, even for low fabrication-induced geometrical changes, both the BIC resonance amplitude and its quality factor (Q-factor) are significantly reduced. We find that the all-dielectric ellipses maintain the highest Q-factors throughout the geometrical variation range, whereas the rod and split ring geometries fall off more quickly. The same behavior is confirmed experimentally, where geometrical variation values are derived from automated processing of sets of scanning electron microscopy (SEM) images. Our methodology provides crucial insights into the performance degradation of BIC metasurfaces when moving from simulations to fabricated samples and will enable the development of robust, high-Q, and easy to manufacture nanophotonic platforms for applications ranging from biomolecular sensing to higher harmonic generation.

In this paper, an all-dielectric metastructure-based high-contrast refractive index sensor is proposed. This structure can be utilized to detect various concentrations of glycerol-water mixtures by evaluating transmission spectral lines and resonant wavelength shifts related with liquid concentration detection. The experimental and calculated results of the developed sensor structure are able to excite three resonance peaks, demonstrating that the structure is capable of reaching excellent sensing capabilities. It has been established that this work has the potential to be useful in medical and biological detection; this is of great scientific and practical significance.

Terahertz waves have widespread applications in various fields ranging from wireless communication to fundamental physics. Achieving bright and broadband terahertz sources still remains a challenge. Recent research has revealed that all‐dielectric metasurfaces with strong electromagnetic resonances and negligible Ohmic loss can enhance nonlinear optical processes and weaken the influences of phase‐matching conditions, providing new opportunities for developing terahertz sources. Here, an all‐dielectric metasurface supporting quasi‐BIC (bound states in the continuum), which enhances terahertz emission in a nonlinear optical film under the excitation of femtosecond laser pulses, is proposed. It is observed that the terahertz emission in lithium niobate (LiNbO3) films is enhanced up to 17 times by a silicon dioxide metasurface and that the terahertz emission enhancement spans the frequency range in 0.1–4.5 THz. This mechanism for the terahertz emission enhancement is attributed to the tight confinement of the pump field in the LNibO3 which is caused by quasi‐BIC resonances. The all‐dielectric metasurface is patterned on the LiNbO3 film instead of etching it, providing a simple way for engineering nonlinear optical processes in LiNbO3. This work paves the way for broadband terahertz emitters. [ABSTRACT FROM AUTHOR]

The advancement of infrared detection technology has imposed increasingly stringent requirements on the infrared radiation regulation materials. Spectral selective emitters can effectively mitigate infrared signals within the detected bands, while simultaneously leveraging undetected band for efficient radiative cooling, thereby enhancing the infrared stealth effectiveness. Herein, we design an all-dielectric selective emitter consisting of only five layers by incorporating the SiO 2 reststrahlen layer with a Ge/MgF 2 photonic multilayers. We quantified the infrared stealth performance of the selective emitter that the emissivity in the undetected band (5−8 μm) is 0.81 and the emissivity values in detected bands are 0.20 (3−5 μm) and 0.17 (8−13 μm), respectively. The simulation results demonstrate that the selective emitter exhibits superior radiative cooling performance and infrared stealth capabilities, as evidenced by significantly lower physical temperature and radiation intensity compared to traditional broadband low emissivity emitters. Furthermore, the all-dielectric structure ensures nearly perfect microwave transmissivity for selective emitters. When combined with microwave absorbers, they exhibit a remarkable microwave absorptivity exceeding 0.9 within the 8−18 GHz range, effectively achieving infrared-microwave compatible stealth. The all-dielectric emitter presents a novel structure for spectral selective infrared radiation control materials, featuring reduced layer complexity and the absence of metallic materials, thereby enhancing its potential for temperature resistance. This work holds significant implications for advancing selective emitters in high-temperature infrared-microwave compatible stealth applications. • We propose a new all-dielectric selective emitter composed of only five layers. • The exceptional spectral selectivity of the selective emitter enhances infrared stealth capabilities. • The selective emitter exhibits lower physical temperature and infrared radiation in high temperature conditions. • The combination of selective emitters and microwave absorbers can effectively achieve infrared-microwave compatible stealth. [ABSTRACT FROM AUTHOR]

Frequency conversion such as harmonic generation is a fundamental physical process in nonlinear optics. The conventional nonlinear optical systems suffer from bulky size and cumbersome phase-matching conditions due to the inherently weak nonlinear response of natural materials. Aiming at the manipulation of nonlinear frequency conversion at the nanoscale with favorable conversion efficiencies, recent research has shifted toward the integration of nonlinear functionality into nanophotonics. Compared with plasmonic nanostructures showing high dissipative losses and thermal heating, all-dielectric nanostructures have demonstrated many excellent properties, including low loss, high damage threshold, and controllable resonant electric and magnetic optical nonlinearity. In this review, we cover the recent advances in nonlinear nanophotonics, with special emphasis on third- and second-harmonic generation from all-dielectric nanoantennas and metasurfaces. We discuss the main theoretical concepts, the design principles, and the functionalities of third- and second-harmonic generation processes from dielectric nanostructures and provide an outlook on the future directions and developments of this research field.

Beam splitters are widely applied in various optical systems as a common beam-splitting device. The conventional stereoscopic and flat-type beam splitters greatly limit the packaging and integration of optical systems due to their large size and restricted emitting direction. Recently, beam-splitting devices made of various transmissive or reflective metasurfaces have shown the potential to overcome these challenges. However, in optical systems such as machine vision, these single-ended beam splitters increase the design complexity of the signal feedback link due to the limitation of the beam-splitting path direction. Here, we proposed and numerically simulated a transflective all-dielectric metasurface beam splitter by applying incompletely transmissive structural designs to the metasurface and using the transmission phase modulation mechanism. It can realize the beam separation for arbitrarily polarized incident light on the same side of the normal at both transmissive and reflective ends with a single-layer unit cell arrangement structure and has a similar emergence angle. The results reveal that at 1550 nm, the angular tolerance bandwidth is about 32°, the total splitting efficiency is over 90%, and the splitting ratio is approximately 1:1. After comparison and verification of simulation results, this transflective metasurface beam splitter is hopeful to be applied in new compact optical systems that require real-time signal feedback, such as coaxial light sources and photoelectric sensing.

An all-dielectric metamaterial absorber based on water resonator encapsulated in resin container is proposed. The absorber can afford the maximum absorption up to 98% at 190 GHz, as well as the wide absorption frequency range from 115 GHz to 300 GHz and a nearly 90% relative absorption bandwidth. The role of water resonator sealed in the resin shell in improving absorption capability is demonstrated by the comparison result that the proposed absorber is superior to pure water or pure resin absorber with the same dimension and interpreted by a further study on the fields and power loss density distributions. Moreover, the proposed absorber can remain excellent absorption performance even for the oblique incidence with large angles. Besides the outstanding absorption performance, the proposed absorber has the advantage of low cost endowed by the use of water, which makes it promising for EM compatibility in the millimetre-wave and high-power cases. [ABSTRACT FROM AUTHOR]

Topological photonics is an emergent field at the cross of photonics and topological physics which opens our eyes to novel topological phenomena and versatile photonic effects. Photonic crystals (PhCs) are the optical analogs of conventional crystals that have proven to be an excellent photonic platform to explore topological physics. Here, we present a brief review of the all-dielectric topological PhCs by focusing on several prominent milestones of topological phases, such as the Su-Schrieffer–Heeger model, topological insulators, topological semimetals, and higher order topological phases. For each topological phase, the topological invariants and the intriguing topological properties as well as the potential applications are discussed. We conclude with the current challenge and the prospect of all-dielectric topological PhCs.

[Display omitted] Recent demonstrations of deep- and vacuum-ultraviolet (DUV and VUV) light emission from artificially engineered meta-atoms through nonlinear harmonic signal generation processes have opened up new avenues for fundamental engineering approaches and modern applications. While many different phenomena based on optical metasurfaces have been revealed in linear optics, several studies have reported the observation of various nonlinear optical phenomena in such nanosystems, like, for example, second and third harmonic generation (SHG and THG), multiphoton luminescence, higher harmonic generation, and four-wave mixing. Plasmonic and all-dielectric flatland metasurfaces enable successful manipulation of light–matter interactions on ultradense platforms and provide substantial enhancement of driving fields, which make these architectures promising and attractive to efficiently radiate intense and coherent second and third harmonic radiations. In this focused Review, we highlight and discuss the recent state-of-the-art methods that have been developed and proposed for the generation of nonlinear harmonic signal and high-energy DUV and VUV lights. This contribution not only summarizes the strategies that have been exploited for augmenting the intensity of nonlinear UV signal, but also introduces the novel mechanisms to strongly optimize the conversion efficiency of this principle. We envisage that this understanding allows to compare the performance of versatile nonlinear DUV and VUV metasources and paves the way of designing much more efficient light emitting tools such as lasers, super-resolution imaging nanosystems, and nanolithography apertures. [ABSTRACT FROM AUTHOR]

A lens antenna (LA) with the characteristics of ultrawide band and high aperture efficiency is proposed in this letter. Moreover, the proposed lens is automatically designed by the genetic algorithm (GA) and finite-different time-domain method, which provides a convenient solution for lens designing. Compared to the feeding ridged horn, the measured gains of the LA are enhanced by 4.4–7.4 dB in the 6–18 GHz band, and the measured aperture efficiencies are also increased by 10%–33% in the band. The maximum aperture efficiency is 92.4% at 6 GHz. Moreover, the 1 dB steady gain band is 13–18 GHz (up to 32.3%). The all-dielectric structure can be easily manufactured using three-dimensional printing technology, which endues the lens with the advantages of low cost, light weight, and easy fabrication. [ABSTRACT FROM AUTHOR]

An all-dielectric transparent metamaterial absorber with encapsulated water is demonstrated in this paper. Because the proposed absorber is realized using only water and polydimethylsiloxane (PDMS) without any conductive patterns, optical transparency is achieved. In addition, the high dielectric loss of water renders it a good candidate for an electromagnetic absorber. The absorptivity is increased by encapsulating the water within the PDMS, and the absorptivity of the proposed absorber is numerically compared with that of the PDMS and water with the same size. When the proposed absorber is realized using two layers, 92.5% absorptivity is achieved at 10.8 GHz, and the absorptivity exceeds 90% in the range of 10.45 to 11.20 GHz, which corresponds to 6.9% bandwidth. Therefore, the proposed absorber has advantages of high transparency, low cost, wide absorption bandwidth, and eco-friendly fabrication.

In this study, an all-dielectric metamaterial absorber consisting of a ring nanocavity array, a spacer layer, and a metallic substrate is designed and investigated. The simulation results show that the two perfect absorption peaks (99.91% and 99.96%) are achieved at 539 nm and 673 nm. The two resonance modes caused by the different electric and magnetic field distributions of the ring nanocavity structure lead to different absorption and sensing properties. In addition, the influence of the structural parameters, such as the width of the nanocavity, on the sensing characteristics was studied and is presented here. A high sensitivity and narrow band result in a huge figure of merit when the proposed absorber is operated as a refractive index sensor.

Water-based absorbers have shown great development potential in the past few years. In this paper, an all-dielectric transparent bi-directional water-based broadband metamaterial absorber is designed. The simulation results indicate that absorptance of the absorber is over 90% in 5.7–41.6 GHz, and its fraction bandwidth is 151.8%. The experimental results are greatly consistent with the simulations. The designed absorber has excellent performances of polarization insensitivity, oblique incidence stability and thermal stability. When the absorptance is more than 0.8, the maximum incident angle reaches 40° in TE mode and is over 60° in TM mode. In 0–80 °C, absorptance of the absorber is hardly changed. Because of the optical transparency of the designed absorber, it can be extensively used in stealth window weapons and electromagnetic compatibility equipment.

We propose and numerically demonstrate a phase-gradient metasurface with high anomalous transmission efficiency and a large anomalous refraction angle that consists of discontinuous regular hexagonal nanorods supported by a silica substrate. The metasurface achieves high anomalous transmission efficiency and a full 2 π phase shift for the wavelength range of 1400–1600 nm. At a central wavelength of approximately 1529 nm, the total transmission efficiency reaches 96.5%, and the desired anomalous transmission efficiency reaches 96.2%, with an anomalous refraction angle as large as 30.64. With the adjustment of the period and the number of nanorods per periodic interval, the anomalous transmission efficiency exceeds 69.6% for a large anomalous refraction angle of 68.58. The superior performance of the proposed design may pave the way for its application in optical wavefront control devices. [ABSTRACT FROM AUTHOR]

We design and numerically investigate an all-dielectric metasurface with a single nanodisk in a unit cell supporting quasi-bound state in the continuum (BIC) arising from the distortion of symmetry-protected BIC. We demonstrate that by breaking out-of-plane symmetry, in the direction perpendicular to a nanodisk with an inclined surface, the transformation of BIC into quasi-BIC, having Fano line-shape, can be observed with an increasing inclination angle. Such transformation is analysed in detail by calculating charge density distributions, far-field radiations and near-field distributions, demonstrating the dominant electric quadrupole component in the quasi-BIC. In addition, the quasi-BIC can be easily tailored by the intrinsic material loss and the Fermi energy of graphene. By introducing this unique degree of freedom beyond the in-plane symmetry, one can realize access to the multipolar BIC-associated leaky state in simpler metasurface, indicating potential applications in the quasi-BIC-based switching and optical modulators. [ABSTRACT FROM AUTHOR]

Due to their extraordinary abilities to manipulate light propagation at the nanoscale, dielectric resonators that generate electric and magnetic Mie resonances for minimal optical loss have recently attracted great interest. Based on an all-dielectric metasurface, made of H-type silicon nanoarrays, this study proposed and constructed a visible-wavelength-range color filter, with high-quality Mie resonance and the ability to synthesize new colors. Using the finite-difference time-domain (FDTD) approach, we can create a larger color gamut by modifying the H-type array’s structural properties. The all-dielectric color filter suggested has a high color saturation and narrow bandwidth. The Mie resonance can be adjusted by manipulating the structural characteristics. By translating the reflectance spectrum into color coordinates and using the CIE1931 chromaticity diagram, a wide range of colors can be generated. This color filter offers a larger color range and saturation than other color filters. We produced color passband filters that span the visible spectrum using Mie resonator arrays, based on an H-type nanoresonator. This technology could have many applications, including high-resolution color printing, color-tunable switches, and sensing systems.