Meta Structure Research Articles

Theoretical analysis of a refractive index sensor based on optical Tamm state of graphene metastructure under arbitrary polarization deflection angle

In this paper, a refractive index sensor based on a metastructure (MS) is proposed, which achieves sensing through the sharp valleys formed in the reflection spectrum by the excitation of optical Tamm states (OTS) by gyroidal graphene. Differences in the refractive index of the filling medium in the pores of gyroidal graphene will cause shifts in the reflection valleys. The graphene layer is followed by a periodic structure consisting of alternating zirconium dioxide (ZrO2) and α-molybdenum trioxide (α-MoO3). The 4 × 4 transfer matrix method (TMM) is used for the calculation of the results, which allows the case of arbitrary polarization deflection angles ϕ to be considered in the discussion. Different values of ϕ can lead to a switch in the dominance of the sensor, specifically, the structure has a larger linear interval but lower sensitivity at ϕ = 0°, which is the opposite of the situation at ϕ = 90°. The sensor can be used in a variety of scenarios such as biochemical sensing, gas detection, etc, and brings the polarization deflection angle of the incident wave into the discussion.

Electromagnetically induced transparent bimodal to unimodal conversion realized by the nematic liquid crystal

In this paper, under the action of a gigahertz (GHz) band circularly polarized (CP) wave, a kind of CP metastructure (MS) is proposed. Recently, the nematic liquid crystal (NLC) has received great attention, but it is still difficult to realize the electromagnetically induced transparency (EIT) bimodal to unimodal under the control of NLC. Through the direct mutual coupling of the metal cross resonator, metal ring resonator, and dielectric cross resonator, modes coupling can be formed and generate transparent windows. Two different EIT states (unimodal and bimodal EIT) accompanied by slow light effects can be observed by regulating the NLC with the applied bias voltage (V bias). When the V bias is 0 V, two transparent windows can be achieved in the 6.595–8.443 GHz and 8.443–10.161 GHz bands. When V bias is 20 V, only one transparent window can be achieved in the 6.891–8.682 GHz band. Due to the high symmetry, the MS has the polarization insensitivity to CP waves. These extremely excellent properties make this MS have a wide application prospect. Noteworthy, the theoretical calculation result of EIT is verified by the two-oscillator theory model and circuit model, the results obtained are basically consistent with the simulation results.

StructSim: Meta-Structure-Based Similarity Measure in Heterogeneous Information Networks

Similarity measures in heterogeneous information networks (HINs) have become increasingly important in recent years. Most measures in such networks are based on the meta path, a relation sequence connecting object types. However, in real-world scenarios, there exist many complex semantic relationships, which cannot be captured by the meta path. Therefore, a meta structure is proposed, which is a directed acyclic graph of object and relation types. In this paper, we explore the complex semantic meanings in HINs and propose a meta-structure-based similarity measure called StructSim. StructSim models the probability of subgraph expansion with bias from source node to target node. Different from existing methods, StructSim claims that the subgraph expansion is biased, i.e., the probability may be different when expanding from the same node to different nodes with the same type based on the meta structure. Moreover, StructSim defines the expansion bias by considering two types of node information, including out-neighbors of current expanded nodes and in-neighbors of next hop nodes to be expanded. To facilitate the implementation of StructSim, we further designed the node composition operator and expansion probability matrix with bias. Extensive experiments on DBLP and YAGO datasets demonstrate that StructSim is more effective than the state-of-the-art approaches.

Introducing Entropy into Organizational Psychology: An Entropy-Based Proactive Control Model.

This paper provides a systematic review of the transfer and quantification of the concept of entropy in multidisciplinary fields and delves into its future applications and research directions in organizational management psychology based on its core characteristics. We first comprehensively reviewed the conceptual evolution of entropy in disciplines such as physics, information theory, and psychology, revealing its complexity and diversity as an interdisciplinary concept. Subsequently, we analyzed the quantification methods of entropy in a multidisciplinary context and pointed out that their calculation methods have both specificity and commonality across different disciplines. Subsequently, the paper reviewed the research on how individuals cope with uncertainty in entropy increase, redefined psychological entropy from the perspective of organizational management psychology, and proposed an "entropy-based proactive control model" at the individual level. This model is built around the core connotation of entropy, covering four dimensions: learning orientation, goal orientation, change orientation, and risk taking. We believe that psychological entropy, as a meta structure of individuals, can simulate, explain, and predict the process of how individuals manage and control "entropy" in an organizational environment from a dynamic perspective. This understanding enables psychological entropy to integrate a series of positive psychological constructs (e.g., lean spirit), providing extensive predictive and explanatory power for various behaviors of individuals in organizations. This paper provides a new direction for the application of the concept of entropy in psychology, especially for theoretical development and practical application in the field of organizational management.

An optimized metastructure switchable between ultra-wideband angle-insensitive absorption and transmissive polarization conversion: a theoretical study.

An optimized metastructure (MS) switchable between ultra-wideband (UWB) angle-insensitive absorption, and transmissive linear-to-circular (LTC) polarization conversion (PC), is proposed, which is a theoretical study. The structural parameters of this MS are optimized by the thermal exchange optimization algorithm. By modulating the chemical potential (μc) of the graphene-based hyperbolic metamaterial embedded in the MS, the MS can achieve UWB absorption in the absorption state and LTC PC in the transmission state. At normal incidence, in the absorption state, the MS exhibits absorptivity exceeding 0.9 within 7-15.45 THz, with a relative bandwidth (RBW) of 75.28%. By elevating μc, an UWB LTC PC is realized, with a RBW of 118.8%, achieving transmittance above 0.9 and the axial ratio below 3 dB. When prioritizing the angular stability, in the absorption state, the MS secures the angular stability of 75° for TE waves and 65° for TM ones. In the transmission state, the angular stability of PC reaches 60°, with RBW = 100.7%. Moreover, by manipulating μc, the tunability of UWB absorption is realized. The optimized MS provides a reference for designing multifunctional intelligent terahertz modulators, with promising application potential in domains like electromagnetic shielding, communication systems, and THz modulation.

Arithmetic logic unit based on the metastructure with coherent absorption.

An arithmetic logic unit (ALU) based on the metastructure (MS) with coherent absorption (CA) is proposed in this Letter. The ALU can perform AND and exclusive OR logical operations at the same frequency point. So it can be regarded as an optical half-adder. By controlling the chemical potential of graphene and the phase difference of coherent electromagnetic waves (EWs), two different binary numbers are input into the ALU. The dynamic absorption peaks, which are generated based on the CA, output the outcomes of the carry-digit bit and non-carry sum bit. This ALU can be used in the field of optical processing and encryption, such as processing hamming code. This given ALU based on the MS with CA has major implications for advancing the study and investigation into the application of CA. Furthermore, it also provides a new, to the best of our knowledge, idea for the study of MS with logical operation.

Switchable multifunctional meta-structure employing vanadium dioxide in the terahertz range

A meta-structure (MS) that can realize a conversion between electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) in the Terahertz (THz) range by utilizing phase-transition vanadium dioxide (VO2) has been reported. This work is controlled by temperature to change the conductivity of VO2 to achieve the switching function. When the VO2 is in the insulator state, the MS is designed to achieve EIT based on the principle of bright mode near-field coupling bright mode. The EIT behavior owns a peak of 0.8 at 0.430 THz with a maximum group delay of up to 6.5 ps. The MS behaves the function of EIA accompanied by the maximum absorption rate of 93.8 % at 0.432 THz while the VO2 film is tuned to the metallic state. The reason for the EIA phenomenon is the magnetic effect of the magnetic dipole generated by the MS in the coupling process. The observed EIT and EIA effects are both theoretically explained by the classic two-oscillator model. In addition, the air columns of the dielectric substrate are utilized for the purpose of frequency approaching. This proposed MS provides a new idea for the design of non-contact regulation and reconfigurable and highly absorbent MSs.

An Ultra‐Wideband Janus Metastructure with Graphene for Detector Based on Anapole Mode in the Terahertz Region

AbstractIn this paper, an ultra‐wideband Janus metastructure (MS) utilizing anapole mode for detector in the terahertz (THz) range by graphene is proposed. Specifically, when Fermi level (Ef) is set to 0.9 eV, the MS demonstrates ultra‐broadband absorption exceeding 0.9 from 0.754 to 5 THz in the −z‐direction with a relative bandwidth of 147.6 %, in which perfect absorption of over 98% develops from 3.24 to 5 THz. In the case of the +z‐direction, the absorptivity maintains around 0.6 within the 0.745 ∼ 5 THz range. As Ef equals 0 eV, the difference in absorption between the −z‐direction and +z‐direction exceeds 0.9 from 4.49 to 4.76 THz. The study also explores the MS for refractive index sensing near 3.71 THz by a unique difference detection, measuring two refractive index ranges: 1.2 ∼ 2.6 and 4.5 ∼ 4.7, with corresponding sensitivities of 0.0450 and 0.0304, respectively. Owing to its highly symmetrical structure, the MS is insensitive to the polarization state of the electromagnetic (EM) waves, performing remarkable angular stability as the incident angle varies from 0 to 60 degrees in the −z‐direction. These splendid properties make the design a good candidate for biomedical sensing, EM cloaking, and full‐space EM wave control.

Transformation of twin-peak electromagnetically induced transparency to twin-peak electromagnetically induced absorption based on magnetic dipole and dielectric resonator

This paper puts forward the transmission from twin-peak electromagnetically induced transparency (EIT) to twin-peak electromagnetically induced absorption (EIA), while it is rare to see the transformation between EIT and EIA in metastructure (MS) in one device in previous articles. With the incidence of TE waves, two transparent windows are generated, ranging from 0.382 THz to 0.986 THz which are separated by 0.604 THz, when the conductivity of vanadium dioxide (VO2) is set to 10 S/m. Two peaks reach 0.864 and 0.934, respectively, accompanied by the largest group delays of the two peaks being 7.55 and 4.54 ps. In addition, VO2 blocks in the metallic state will affect interference paths between energy levels, contributing to the formation of EIA, then maintaining a common absorption of 0.607 at 0.429 THz and 0.904 at 0.678 THz. Under the combined action of the dielectric resonator and metal resonator, the conversion from bimodal EIT to bimodal EIA is hardly been researched, at the same time, the adoption of the circuit model and the four-level theory proves the rationality of the model. The transformation from EIT to EIA is aroused by changing the state of VO2, promising broad prospects in multifunctional devices.

Broadband electromagnetically induced transparency to broadband electromagnetically induced absorption conversion with silicon based on metastructure

Electromagnetically induced transparency-like (EIT-like) and electromagnetically induced absorption-like (EIA-like) can be easily generated separately in metastructure (MS), but it is rare to achieve both states simultaneously in a single device, let alone broadband EIT-like and EIA-like. Notably, the responses of the left-handed circularly polarized waves and the right-handed circularly polarized waves to the MS are the same, demonstrating the generation of polarization-insensitive EIT-like and EIA-like. The photosensitive silicon (Si) is chosen to control the state of the device, realizing the mutual conversion between EIT-like and EIA-like. With the incidence of circularly polarized (CP) waves, the broadband EIT-like can be observed between 0.505 THz and 1.403 THz, where the maximum group delay and group index can arrive at 1.57 ps and 7.26, respectively. Besides, the transition from broadband EIT-like to broadband EIA-like can be successfully achieved in the same frequency band when Si is excited by the pump light, where Si-based ladder structure (SBLS) is adapted to enhance absorption efficiency to realize broadband EIA-like. The relative bandwidths of EIT-like and EIA-like have reached 26.5% and 15.2%, respectively. The theoretical RLC (resistance, inductance, and capacitance) equivalent circuit model demonstrates the feasibility of broadband EIT-like and EIA-like implementation.

Frequency Reconfigurable and Multifunctional Metastructure Regulated by Nematic Liquid Crystal: Broadband Circular to Linear Polarization Converter

AbstractWith the tunability of the nematic liquid crystal (NLC), a broadband frequency reconfigurable and versatile metastructure (MS) is proposed and theoretically investigated in this paper, combining circular‐to‐linear (CTL) polarization conversion (PC) and circular‐to‐circular (CTC) PC simultaneously. The MS is composed of two via‐coupled modules, which can respond differently to the incident waves. Each module is connected utilizing a metal via a column, thus exceedingly enhancing the energy transmission and reducing the loss when transmitting. When the applied bias voltage (Vbias) is 0 V, the NCL molecules follow the initial orientation. The MS converts the incident right circular polarized (RCP) waves into linear polarized (LP) waves within 8.11–9.95 gigahertz (GHz) with a relative bandwidth of 20.38% and achieves the PC of left circular polarized (LCP) into RCP waves. As the Vbias reaches 20 V, the original operating interval reconfigures and shifts overall toward a lower frequency. The bandwidth of CTL is 7.66–9.02 GHz, and the CTC PC is broadened to 20.20%. Meanwhile, the structure justification is verified, and the inducing mechanism of PC is expounded. Possessing the merits of versatile collaborative processing and wide operating bands, such an MS is promising to be a polarization‐controlled application candidate and enrich multifunctional designs.

Tunable Transmissive Metastructure for Precise or Broadband Polarization Conversion Modulation Based on Graphene

AbstractBased on the principle of Fabry–Perot (F–P) cavity resonance and the selective permeability of gratings to specific electromagnetic waves, a graphene‐based metastructure (MS) is proposed for transmissive polarization conversion (PC). Using the full‐wave numerical simulation, it is found that by varying the Fermi energy of graphene, the effective resonance range of the suggested MS can be dynamically adjusted from 0.47 to 0.348–0.714 THz, achieving the target of precise to ultra‐broadband polarization modulation. In this paper, the plausibility of the structure is verified from multiple perspectives, and the correlation analyses of the electric and magnetic fields are the supporting illustrations. Additionally, the triggering mechanism of PC is visually illustrated in the study of the surface currents distributions. Simulation results reveal that the MS is superior in performance, functionality, and principle, and it is foreseen to hold excellent promise for integrated equipment in the terahertz (THz) band.

Broadband plasmon-induced transparency to an anapole mode induced absorption conversion Janus metastructure by a waveguide structure in the terahertz region.

A Janus metastructure (MS) assisted by a waveguide structure (WGS) resting on anapole modes and exhibiting direction-dependent behavior has been developed in the terahertz (THz) region. Ultra-broadband absorption is formed by the destructive interference through the anapole as well as Janus trait and is shaped by nested WGS. In this design, vanadium dioxide (VO2) is expected to attain functional transformation from plasmon-induced transparency (PIT) to absorption. The insulating nature of the VO2 results in the creation of the PIT, which is characterized by a wide and high transmission window ranging from 1.944 THz to 2.284 THz, corresponding to the relative bandwidth of 7.4% above 0.9. However, when the VO2 reaches the metallic state, a high absorptivity of 0.921 at 2.154 THz can be implemented in the -z-direction owing to the excitement of the toroidal dipole and electric dipole moments in the near-infrared region. And in the +z-direction, the broadband absorption above 0.9 in the 1.448-2.497 THz range takes shape in virtue of surface plasmon polariton modes, in which intensely localized oscillation of free electrons is confined to the metal-dielectric interface supported by the WGS. Noting that the MS is equipped with a favorable sensitivity to the incidence angle, we develop an ultra-broadband backward absorption in the TM mode from 0.7-10 THz nearly all above 0.9 when the incidence angle changes from 30°-70°. Moreover, owing to the highly symmetrical structure, the MS exhibits exotic polarization angular stability. All the awesome properties make this MS a good candidate for various applications such as in electromagnetic wave steering, spectral analysis, and sensors.

Transition from electromagnetically induced transparency to Electromagnetically Induced Absorption Utilizing Phase-Change Material Vanadium Dioxide Based on Circularly Polarized Waves

A circular-polarization metastructure (MS) with switchable functions connected to the transition from electromagnetically induced transparency (EIT) to electromagnetically induced absorption (EIA) is theoretically proposed under the action of circularly polarized (CP) waves in the terahertz (THz) band. Additionally, we use the phase-change material vanadium dioxide (VO 2 ) to achieve functional transformation. The MS is mainly composed of two metal bright modes and a VO 2 resonator. When the VO 2 is insulating, the EIT with a high and wide transmission window is realized between 0.460 THz and 0.911 THz due to the coupling between two bright modes. Once VO 2 reaches the metal state, the original high transmission window is transformed into the high absorption window and the phenomena from EIT to EIA (vice versa) are successfully achieved from 0.460 THz to 0.911 THz. The group delays and group index of EIT are 161 ps and 1126, respectively. The simulation results of EIT and EIA are verified by fitting the theoretical two-oscillator model. • The proposed MS provides a new idea to manipulate the transition between EIT and EIA. • Multiple parameters can be adjusted to manipulate the transmission amplitude and frequency. • The presented structure is great transparency or absorption for the EM wave. • The thickness of the proposed MS is subwavelength. • The proposed MS can be applied to antenna fields and wave plates.

Non-adiabatic dynamics simulations of the S1 excited-state relaxation of diacetyl phenylenediamine.

The small molecule built around the benzene ring, diacetyl phenylenediamine (DAPA), has attracted much attention due to its synthesis accessibility, large Stokes shift, etc. However, its meta structure m-DAPA does not fluoresce. In a previous investigation, it was found that such a property is due to the fact that it undergoes an energy-reasonable double proton transfer conical intersection during the deactivation of the S1 excited-state, then returns to the ground state by a nonradiative relaxation process eventually. However, our static electronic structure calculations and non-adiabatic dynamics analysis results indicate that only one reasonable non-adiabatic deactivation channel exists: after being excited to the S1 state, m-DAPA undergoes an ultrafast and barrierless ESIPT process and reaches the single-proton-transfer conical intersection. Subsequently, the system either returns to the keto-form S0 state minimum with proton reversion or returns to the single-proton-transfer S0 minimum after undergoing a slight twist of the acetyl group. The dynamics results show that the S1 excited-state lifetime of m-DAPA is 139 fs. In other words, we propose an efficient single-proton-transfer non-adiabatic deactivation channel of m-DAPA that is different from previous work, which can provide important mechanistic information of similar fluorescent materials.

A Meta-Structure-Based Frequency Doubler With Low Input Power

As the operating frequency increases, the output power of traditional frequency doublers becomes too low to drive the next stage devices. To address this problem, a double-layer meta-chip circuit consisting of a symmetrical split ring (SSR) structure with a doubler circuit is presented. It combines the transmission mode in the rectangular waveguide with the resonance mode in the meta structure. The meta structure improves the coupling efficiency between the diode and electromagnetic energy, strengthens the electric field at the diode, and ultimately enhances the efficiency of the frequency doubler at low input power. From 160–180 GHz, the experiments show that the frequency doubler with SSR achieved a peak efficiency of 22.4% with an output power of 10.6 mW. Its performance of maximum output power is 45.2% better than the traditional structure, which provides an important technical approach to achieve higher efficiency at low input power.

METAL SURFACE DEFECT DETECTION USING DEEP LEARNING

The purpose of the proposed work is to apply a deep learning technique to quickly and accurately detect surface faults. The Shot MultiBox Detector (SSD) network was chosen and fused with the convolution neural network (CNN) MobileNet to generate the MobileNet-SSD because of the meta structure. A surface defect detecting technique was then planned, mostly employing the MobileNet-SSD. The network topology and settings were changed to form the detection model since the SSD's structure was optimized without sacrificing accuracy. The proposed technique was utilized to detect common defects on a container's protection surface, such as breaches, dents, burrs, and abrasions, within the filling line. The results reveal that our method is more accurate and faster than lightweight network methods and classic machine learning methods at detecting surface faults. The findings add to our understanding of fault detection in real-world industrial settings.

Enhancement of microwave absorption bandwidth of MXene nanocomposites through macroscopic design.

MXene, the new family of two-dimensional materials having numerous nanoscale layers, is being considered as a novel microwave absorption material. However, MXene/functionalized MXene-loaded polymer nanocomposites exhibit narrow reflection loss (RL) bandwidth (RL less than or equal to −10 dB). In order to enhance the microwave absorption bandwidth of MXene hybrid-matrix materials, for the first time, macroscopic design approach is carried out for TiO2-Ti3C2Tx MXene and Fe3O4@TiO2-Ti3C2Tx MXene hybrids through simulation. The simulated results indicate that use of pyramidal meta structure of MXene can significantly tune the RL bandwidth. For optimized MXene hybrid-matrix materials pyramid pattern, the bandwidth enhances to 3–18 GHz. Experimental RL value well matched with the simulated RL. On the other hand, the optimized Fe3O4@TiO2-Ti3C2Tx hybrid exhibits two specific absorption bandwidths (minimum RL value - −47 dB). Compared with other two-dimensional nanocomposites such as graphene or Fe3O4-graphene, MXene hybrid-matrix materials show better microwave absorption bandwidth in macroscopic pattern.

Semi-Supervised Learning on Meta Structure: Multi-Task Tagging and Parsing in Low-Resource Scenarios

Multi-view learning makes use of diverse models arising from multiple sources of input or different feature subsets for the same task. For example, a given natural language processing task can combine evidence from models arising from character, morpheme, lexical, or phrasal views. The most common strategy with multi-view learning, especially popular in the neural network community, is to unify multiple representations into one unified vector through concatenation, averaging, or pooling, and then build a single-view model on top of the unified representation. As an alternative, we examine whether building one model per view and then unifying the different models can lead to improvements, especially in low-resource scenarios. More specifically, taking inspiration from co-training methods, we propose a semi-supervised learning approach based on multi-view models through consensus promotion, and investigate whether this improves overall performance. To test the multi-view hypothesis, we use moderately low-resource scenarios for nine languages and test the performance of the joint model for part-of-speech tagging and dependency parsing. The proposed model shows significant improvements across the test cases, with average gains of -0.9 ∼ +9.3 labeled attachment score (LAS) points. We also investigate the effect of unlabeled data on the proposed model by varying the amount of training data and by using different domains of unlabeled data.

Weighted meta paths and networking embedding for patent technology trade recommendations among subjects

Most patent technology recommendations are based on link prediction of a homogeneous trade network and multiple-attribute matching. We constructed a heterogeneous information network (HIN) with four types of nodes and seven types of relations; designed a heterogeneous relation traversal algorithm based on the meta paths and meta structures inspired by the depth first search (DFS) strategy; obtained subject-relation sequences; and then calculated the weight of each meta path and meta structure through logistic regression. Using the relation sequence corpus of the weighted meta paths and meta structures among subjects, the patent technology trade recommendation model based on network embedding (PSR-vec) was proposed. The model was trained by using the Skip-gram method to obtain a vector-space representation for all subjects. Finally, the recommendation target was achieved by measuring the cosine similarity of the subject vectors. Through empirical research on the electronic information patent data, we observed that the PSR-vec model with weighted meta paths and meta structures was more precise than that with a single meta path or meta structure, which indicated that the patent technology trade was influenced by multiple factors. Second, the PSR-vec model combining weighted meta paths and meta structures was more precise than the unweighted model, which reflected more differences in multiple factors affecting trade. Third, compared to Deep Walk, Node2vec, Metapath2vec, and GraphSAGE methods, the PSR-vec model had a higher precision of up to 80%. Eventually, the recommendation subjects of PSR-vec included the holding relation, the supply relation, and the loose relation, which increased the diversity of the recommendation results. Our research thus provided a decision-making method for effective docking among patent technology trade subjects.