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In 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. [ABSTRACT FROM AUTHOR]

In this paper, a refractive index (RI) sensor with superconducting photonic crystal in the terahertz regime is theoretically analyzed by the transfer matrix method. An asymmetric resonance cavity containing gradient thicknesses of the superconducting layer is employed to suppress the resonance absorption linewidth. We present the coupled wave theoretical model to give an optimization scheme for excellent sensing performance. The proposed sensing models can achieve an excellent single resonant peak when the temperature is over 80 K. When the incident angle varies between 50° and 70° in TE mode, the shift of a single resonant peak has a linear relationship with the incident angle. The simulation results report that the sensitivity and figure of merit in the optimal model can reach over 22.2 μm RIU−1 (RIU represents RI unit) and 265 at the ultralow temperature (85 K), respectively. Its performance indicators are dozens of times those of the traditional photonic crystal RI sensor. Our study provides theoretical guidance for the design of a low-temperature RI sensor with a high-performance indicator. [ABSTRACT FROM AUTHOR]

Photonic spin Hall effect (PSHE) is an effective metrological tool to characterize the variation in weak refractive index (RI) and nanostructure parameters. In this Letter, a highly sensitive terahertz Janus sensor (JS) based on PSHE is proposed. Through the asymmetric arrangement of different dielectrics, the sensor has a Janus feature, realizing the multitasking of thickness and RI detection on multiple scales. When electromagnetic waves (EWs) are incident into the JS from the forward scale, the number of graphene layers (1–7 layers) can be exactly identified by thickness detection. Enhancing the PSHE by the property of graphene, the JS can extend the thickness change of the graphene layer at the nanometer level by 106 times to the millimeter level with a sensitivity of 3.02 × 10−3 m/nm. In the case of EWs backward scale propagation, based on the sensitivity of 6.244 × 10−3 m/RIU, the JS can identify different kinds of waterborne bacterium such as Vibrio cholerae, Escherichia coli, and Shigella flexneri, in the RI range of 1.355–1.43 with high precision. The design of the multiscale and multitasking JS with high sensitivity is of great significance for accelerating the research and exploration of graphene materials. In addition, it provides an idea for real-time, no-label, and low-cost detection in the biomedical field. [ABSTRACT FROM AUTHOR]

We propose magnetized gyromagnetic photonic crystals (MGPCs) composed of indium antimonide (InSb) and yttrium iron garnet ferrite (YIGF) layers, which possess the properties of nonreciprocal wide-angle bidirectional absorption. Periodical defects in the MGPCs work as filters. Absorption bands (ABs) for the positive and negative propagations arise from the optical Tamm state and resonance in cavities respectively, and they prove to share no overlaps in the studied frequency range. Given ω = 2.0138 THz, for the positive propagation, the ABs in the high-frequency range are localized in the interval between 0.66 ω and 0.88 ω. In the angular range, the ABs for the TE and TM waves reach 60° and 51°, separately. For the negative propagation, the ABs in the low-frequency range are localized in the interval between 0.13 ω and 0.3 ω. The ABs extend to 60° for the TE waves and 80.4° for the TM waves. There also exists a narrow frequency band in a lower frequency range. The relevant factors, which include the external temperature, the magnetic fields applied to the YIGF, the refractive index of the impedance matching layer, and the defect thickness, are adjusted to investigate the effects on the ABs. All the numerical simulations are based on the transfer matrix method. This work provides an approach to designs of isolators and so on. [ABSTRACT FROM AUTHOR]

A layered metastructure (LM) formed by a quasi‐periodic arrangement of graphene and isotropic dielectric mediums, which can realize the functions of the tunable logic gate and refractive index (RI) sensing based on spin Hall effect (SHE), is theoretically studied. The asymmetric arrangement of the mediums and the increased angle of the incident electromagnetic waves (EWs) equip the LM with Janus feature. Through the modulation of the graphene chemical potential, the sharp absorption peak (AP) in the terahertz (THz) range can be obtained, and then the AP can be used to implement NOT logic and OR logic respectively corresponding to the forward and backward scales. By locating the incident angle of light corresponding to the SHE displacement peak, the linear measurement relationship between RI and SHE angle can be realized, and the widest RI measurement range is 1–1.4 with the angles changing from 21.88° to 61.84°. Additionally, a good linear range can be achieved, owning the optimum sensitivity (S) up to 153.5° RIU−1. The RI sensing still strictly follows the logic functions of the forward NOT and backward OR via adjusting the chemical potential of graphene and discriminating the peak value of SHE displacement. [ABSTRACT FROM AUTHOR]

In this paper, a Janus metastructure (JMS) is proposed that can act both as a logic gate and detect multiple physical quantities. By adjusting the incident angle of electromagnetic waves, arranging the dielectrics asymmetrically, and using the anisotropy of the plasma, the Janus function can be obtained, which gives the metastructure a multiscale property. Sharp transmission peak (TP) is generated by located defect mode resonance. The AND logic gate on the positive and negative scales can be realized by judging the TP value. By locking the point frequency of the TP, the refractive index, magnetic field strength, incident angle, and plasma density can be detected simultaneously on the two scales in the GHz range, which is rarely studied. Good sensing performances are also owned, and the corresponding optimal sensitivities are 0.095 (2πc/d)/RIU, 9.42 × 10−3 (2πc/d)/T, 1.48 × 10−3 (2πc/d)/°, and 0.035 (2πc/d) m3/1019, respectively. Compared with the traditional sensors, the proposed JMS equipped with two scales not only can realize the logic gate but also measure multiple physical quantities, which has a certain application potential. [ABSTRACT FROM AUTHOR]

The direction-dependent dual-mechanism refractive index sensor composed of the forward strip graphene and backward composite photonic structure with black phosphorus (BP) is proposed. The linear correlation between the absorption by different mechanisms and the refractive index of the analyte can be realized for two incident directions. The simulated results show that the sensitivities of the forward incidence with the refractive index measurement ranges of 1.2 - 1.6 and 1.6 - 1.9 are 3.135 THz/RIU (refractive index unit) and 1.135 THz/RIU. The sensitivities of the backward incidence with refractive index detection zones 1.2 - 1.5 and 1.6 - 2.0 are 9.500 THz/RIU and 14.650 THz/RIU. In addition, the forward incidence owns more appropriate linearity while the backward incidence possesses better angular stability. These results can find applications in reconfigurable integrated photodetectors for refractive index sensing. [ABSTRACT FROM AUTHOR]

In this paper, a novel magnetized ferrite photonic crystal sensing structure is proposed. Based on the evanescent coupling, the discrete absorption evanescent waves with high absorptance are theoretically investigated. Different from universal transmission evanescent waves’ researches, the absorption mechanism is more suitable for the design of the electromagnetic device and is also rarely studied. Thus, the absorption evanescent wave is scarce and novel, deserving to be explored. Furthermore, most conventional sensors hold single scale, multiscale sensors will have extensive application. Due to the magneto-optical effect and asymmetric arrangement, the symmetry of the reverse distribution of space and time is broken, the nonreciprocity is attained. The sensor proposed can measure the refractive index and magnetic flux density at the forward and backward scales, which is rarely implemented by previous sensors. The combination of multifunction and multiscale is very novel and valuable. Besides, adopting the transfer matrix method, the sensitivity, linear range, quality factor value, and figure of merit are numerically analyzed. Owing to the absorption evanescent wave, the highest quality factor value in the refractive index detection can reach 59473, and the detection limit can achieve about 0.00000884, which means extremely accurate measurements. It is worth emphasizing that the novelty of the multifunctional sensor is the nonreciprocal absorption evanescent wave sensor, which achieves the measurement of refractive index and magnetic flux density of different scales with superior performance, different linear ranges, and different detection limits in the same linear range. Thus, it has enormous applications in fuel gases concentration detection, biological detection, and other sensing fields. [ABSTRACT FROM AUTHOR]

In this paper, we apply the scatterers of cylindrical rings to a two-dimensional photonic crystals slab. The effects of the number of layers, the thickness, the index, and the height of the cylindrical layers on the photonic band gaps (PBGs) of such slab with different lattice arrangements are studied. It turns out that our new structure helps to obtain a large range of the PBGs. The maximum bandwidth is obtained with the value of 0.117 (2πc/a). The PBGs are moved to the lower frequencies with the augment of thickness, refractive index, and height. The choice of height, refractive index, and thickness is a trade-off, and adding the number of dielectric layers is not always positively correlated with the area of PBGs. In addition, in the W1 waveguide with a triangular lattice layout, we obtain a slow light of 0.026 × c. Compared with the square lattice, the triangular lattice is more suitable for slowing down the speed of light. [ABSTRACT FROM AUTHOR]

In this article, a novel nonlinear model is proposed to describe the permittivity of the plasma, and the nonlinear optical bistable phenomenon of the 1-D photonic crystals, which is composed of a nonlinear plasma defect layer, is theoretically investigated by the conventional transfer matrix method (TMM) under TM wave. It is figured out that the permittivity of nonlinear plasma exists in bistable state. Then, the tuning effects of the number of the photonic crystals’ (PCs) periodic layers, the incident frequency, the thicknesses of the nonlinear plasma layer, and the incident angle on the optical bistability (OB) have been emphatically studied. Additionally, the transmission and the reflectance under the influences of this bistable tuning are further proposed. The calculated results show that the adjustment of the OB can be achieved without changing the multi-layer material geometry. This multi-composite nonlinear plasma defect structure with the tunable bistable phenomenon can be applied to numerous valuable optical devices, such as novel optical power threshold devices, logic gates, and optical information memory. [ABSTRACT FROM AUTHOR]

In this article, a structure based on one-dimensional photonic crystals that can be used for both angle sensing and refractive index sensing is proposed, which is achieved by optical Tamm state. Under Bragg scattering, its features are investigated by the transfer matrix method. This sensing structure is based on a multi-frequency absorption structure, which can achieve an absorption rate higher than 0.9 for three to four frequency points at the same time. The studied results demonstrate that the absorption peaks of such an absorption structure can be changed from three to four by adjusting the number of periods and silver layer thickness. Absorption peaks can occur red and blue shifts employing tailoring the thickness of defect and the angle of the incident light. By altering the thickness of the defect and the number of periods, the interval between the absorption peaks can be dominated. They are all with high-quality factors and can be used to bring about a high absorption sensor for the refractive index or angle. When it acts as a refractive index sensor, the operating range can cover from 2 to 2.7, whose sensitivity and average figure of merit are 32.3 THz/RIU and 100. If the presented device is used as an angle sensor, those values will become 0.5 THz/degree and 1.2, and its measuring range is from 25° to 70°. It can be said that the emergence of this special sensing structure will be possible to have a broad application prospect in the field of measurement. [ABSTRACT FROM AUTHOR]

Recently, the metastructure absorbers (MSA) have opened up a new sensing approach, whereas the existing designs suffer from a short numerical measurement range and small sensitivity span. In this paper, a photoexcited MSA that enables a transition between three operating states in the terahertz (THz) regime is proposed. The MSA merges two kinds of photosensitive semiconductor materials embedded in the split ring structure. By adjusting the wavelength of the pump light, semiconductor materials can be excited thus realizing the mutual change of three states in absorption. The structure appears to dual peaks absorption at normal incidence with absorptivity of 95.32% at 0.9269 THz and 99.42% at 1.5586 THz without the illumination of the pump light. Furthermore, it is worth emphasizing that we introduce a novel idea to utilize this actively tunable MSA for refractive index sensing. Not only it has the advantage of large sensitivity variation from 0.0471 (THz/RIU) to 0.1239 (THz/RIU) but also it can be applied in five different refractive index numerical measurement ranges spanning from 1 to 4 with preferable performance. Finally, the absorption effect of the MSA is analyzed under different incidence and polarization angles. • Tunability of three states using two photosensitive materials can be achieved. • Refractive index sensing with large sensitivity variation in five different refractive index. • The design has superb tolerance of the angular stability. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the properties of anisotropic photonic band gaps (PBGs) for three-dimensional (3D) photonic crystals (PCs) composed of the anisotropic positive-index materials (the uniaxial materials) and the epsilon-negative (ENG) materials with body-centered-cubic (bcc) lattices are theoretically studied by a modified plane wave expansion (PWE) method, which are the uniaxial materials spheres inserted in the epsilon-negative materials background. The anisotropic photonic band gaps (PBGs) and one flatbands region can be achieved in first irreducible Brillouin zone. The influences of the ordinary-refractive index, extraordinary-refractive index, filling factor, the electronic plasma frequency, the dielectric constant of ENG materials and the damping factor on the properties of anisotropic PBGs for such 3D PCs are studied in detail, respectively, and some corresponding physical explanations are also given. The numerical results show that the anisotropy can open partial band gaps in such 3D PCs with bcc lattices composed of the ENG materials and uniaxial materials, and the complete PBGs can be obtained compared to the conventional 3D PCs containing the isotropic materials. The calculated results also show that the anisotropic PBGs can be manipulated by the parameters as mentioned above except for the damping factor. Introducing the uniaxial materials into 3D PCs containing the ENG materials can obtain the larger complete PBGs as such 3D PCs with high symmetry, and also provides a way to design the tunable devices. [Copyright &y& Elsevier]

Abstract: In this paper, the properties of photonic band gaps (PBGs) for three-dimensional magnetized plasma photonic crystals (MPPCs) composed of anisotropic dielectric (the uniaxial material) spheres immersed in homogeneous magnetized plasma background with simple-cubic lattices are theoretically investigated by the plane wave expansion (PWE) method, as the Voigt effects of magnetized plasma are considered. The equations for calculating the anisotropic PBGs in the first irreducible Brillouin zone are theoretically deduced. The anisotropic PBGs and two flatband regions can be obtained. The effects of the ordinary-refractive index, extraordinary-refractive index, filling factor, plasma frequency and plasma cyclotron frequency on the characteristics of anisotropic PBGs for the three-dimensional MPPCs are studied in detail and some corresponding physical explanations are also given. The numerical results show that the anisotropy can open partial band gaps in simple-cubic lattices and the complete PBGs can be found compared to the conventional three-dimensional MPPCs doped by the isotropic material. The bandwidths of PBGs can be enlarged by introducing the magnetized plasma into three-dimensional PCs containing the uniaxial material. It is also shown that the anisotropic PBGs can be manipulated by the ordinary-refractive index, extraordinary-refractive index, filling factor, plasma frequency and plasma cyclotron frequency. The locations of flatband regions cannot be tuned by any parameters except for the plasma frequency and plasma cyclotron frequency. Introducing the uniaxial material in three-dimensional magnetized plasma-dielectric photonic crystals can enlarge the PBGs and also provide a way to obtain the complete PBGs as the three-dimensional MPPCs with high symmetry. [Copyright &y& Elsevier]

In this paper, the dispersive properties of three-dimensional (3D) magnetized plasma photonic crystals (MPPCs) composed of anisotropic dielectric (the uniaxial material) spheres immersed in homogeneous magnetized plasma background with face-centered-cubic (fcc) lattices are theoretically investigated by the plane wave expansion method, as the Voigt effects of magnetized plasma are considered. The equations for calculating the anisotropic photonic band gaps (PBGs) in the first irreducible Brillouin zone are theoretically deduced. The anisotropic PBGs and two flatbands regions can be obtained. The effects of the ordinary-refractive index, extraordinary-refractive index, filling factor, plasma frequency, and external magnetic field on the dispersive properties of the 3D MPPCs are investigated in detail, respectively, and some corresponding physical explanations are also given. The numerical results show that the anisotropy can open partial band gaps in 3D MPPCs with fcc lattices and the complete PBGs can be found compared to the conventional 3D MPPCs doped by the isotropic material. The bandwidths of PBGs can be tuned by introducing the magnetized plasma into 3D PCs containing the uniaxial material. It is also shown that the anisotropic PBGs can be manipulated by the ordinary-refractive index, extraordinary-refractive index, filling factor, plasma frequency, and external magnetic field, respectively. The locations of flatbands regions cannot be manipulated by any parameters except for the plasma frequency and external magnetic field. Introducing the uniaxial material can obtain the complete PBGs as the 3D MPPCs with high symmetry and also provides a way to design the tunable devices. [ABSTRACT FROM AUTHOR]

• A new GH GDM method is also introduced. • The GDM method improves accuracy and provides a third window with increased sensitivity. • The function realization of a polarization isolator is proposed. • High sensitivity polarization conversion of reflected waves can obtain. To address the increasing demand for micro-detection with high accuracy and bridge the gap in the application of topological photonics to Goos-Hänchen (GH) effects, an unprecedented Janus multi-transconductor predicated on the novel one-dimensional quasi-conjugate topological photonics crystals (1D QTCs) operating in the terahertz band is established. Calculated by the transfer matrix and stationary phase methods, the proposal sets forth a multi-transduction scheme correlating double physical parameters including refractive index, and magnetic field intensity with the polarization state and GH lateral shift. As a GH amplitude transconductor, antipodal enhanced GH shift values with disparate orders of magnitude and sensitivities are elicited in the forward incidence (FI) and backward incidence (BI) modes, and the GH differential measurement (GDM) method is first introduced to expand the detection window. Moreover, the Jauns sensitivity could be seamlessly modulated by the external magnetic field of the indium antimonide layer. As a polarization transconductor, manipulating the two physical parameters could result in polarization conversion in BI mode, but only quasi-LPWs are obtained in FI mode. Conversely, the polarization state could transduce the physical parameters and GH shift. The proposal constitutes an invaluable reference for advancing the application of topological photonics and the GH effect. [ABSTRACT FROM AUTHOR]

In this proposal, we introduce a Janus layered metastructure (JLM) composed of three distinct structures. The first and third structures (S1 and S3) are designed based on Brewster and Bragg reflection laws, which enable the selection of a specific incident angle of electromagnetic waves (EMWs) by adjusting the refractive indices of the materials. By matching the thickness of the dielectric layer to the optical wavelength, S 1 , and S 3 operate across the 30–300 μm band, achieving angle selection (AS) of EMWs in the THz band. The second structure (S 2) consists of a single layer of graphene and SiO 2 arranged in quasi-periodic sequences, which absorbs EMWs in the THz band and achieves broadband absorption without angle sensitivity. By combining the characteristics of these three structures, we achieve a broadband directional thermal radiation covering the 30–300 μm band. Additionally, the adjustability of the AS of S1 and S3 and the absorption effect of S2 enable Janus ultra-wideband tunable directional thermal radiation at large angles depending on the specific needs. • The proposed JLM has realized directional thermal radiation. • The direction of thermal radiation can be adjusted easily by changing the refractive index of composed materials. • The relative radiation band is 10 (30–300 μm). • Both sides of the JLM can be adjusted independently to suit different application scenarios. [ABSTRACT FROM AUTHOR]

In this work, a multifunctional metastructure (MS) that combines the functions of a circular-to-linear polarization conversion (PC) and sensing is presented. The device uses a 2 × 2 array of three layers of media as the unit structure to modulate an incident circularly polarized wave into a linearly polarized one by reflection in the terahertz (THz) band. Its output linear polarized wave axial ratio (AR) is larger than 20 dB in the 1.61–2.638 THz range, with a relative bandwidth of 48% and an insertion loss below 4%. In addition, filling the device with liquids of different refractive indices shifts the frequency of the sharp AR peak generated by its output linear polarized wave. Utilizing this property, the device can also be used a refractive index sensor. When the thickness of the liquid to be measured is 2 μm, the device has a frequency sensitivity of 178 GHz/RIU (refractive index unit) and a figure of merit (FOM) of 12.7. Parameters and angles are also discussed and the principle is analyzed through current density plots. The given design can be applied in satellite communication systems, signal modulation, and sensing. • The MS achieves circular-to-linear polarization conversion. • The MS realizes refractive index sensor. • The MS realizes a multifunctional device combining a circular-to-linear polarization converter and a sensor. • The MS discusses the effect of different parameters as well as angles on performance. [ABSTRACT FROM AUTHOR]

• The proposed LPS can achieve the function of isolator and switch with one structure. • The presented LPS has the angle stabilization. • The presented LPS enable high isolation, extinction ratio and low insertion loss. • Multiple parameters can be adjusted to manipulate the transmission frequency and bandwidth. • The proposed LPS can be applied to the area of communication and computer. In this paper, a multifunctional device based on a one-dimensional (1-D) magnetized InSb layered photonic structure (LPS) that can achieve the function of a magnetic-controlled isolator and switch is proposed, with the advantages of multi-function. The external conditions for realizing the LPS function are temperature 303 K, magnetic field B 1 = 0–0.3 T, B 2 = 0 T, which are easier to obtain through an applied magnetic field device. B 1 and B 2 differ only in intensity. Both B 1 and B 2 are applied magnetic fields parallel to the positive y -axis. The change of magnetic field can influence the the cyclotron frequency of the electron which affect the dielectric constant of the tensor form, and finally lead to the change of refractive index (RI), resulting in interesting electromagnetic phenomena. Temporal inversion symmetry and spatial inversion symmetry could be easily broken to actualize nonreciprocal phenomena because of the magneto-optic effect of Indium antimonide (InSb) and an asymmetric arrangement of quasi-periodic media. For the isolator, the transmittance of forwarding propagation arrives at 0.994 and the backward scale is much closer to 0. The isolation and insertion loss achieves 34 dB and 0.0269 dB, and the range of the angle stabilization is from 17° to 31°. For the switch operating, just changing the value of B 1 from 0.3 T to 0 T, can realize the function of the switch operating instead of an isolator. This shift is easier to reach by turning off the magnetic field. The extinction ratio attains 99.8 % and angle stabilization is between 9° and 31°. This magnetic-structure multifunctional LPS can play a vital constructive role in medicine, computing, and other fields. [ABSTRACT FROM AUTHOR]

• A multichannel one-way and wide-angle absorber in THz regime with the cascading quasi-periodic structure containing superconducting layers is theoretically realized. • The features of one-way multi-band absorption can be tuned by the ambient temperature of superconducting layers and the thicknesses of different dielectrics. • The RBWs of the unidirectional absorption regions located in lower, middle and high frequencies can reach to 51.94%, 30.18%, 19.12% when T S =90 K and T U =10 K, respectively. • The wide-angle absorption is polarization-dependent, the maximum angle that the TE and TM waves can sustain in the absorption region is 76° and 84°, separately. • The absorptance in two opposite transmission directions can be enhanced with the augment of superconducting layers' operating temperature. • It is feasible to form multiple Fabry-Perot resonance cavities via splicing two kinds of quasi-periodic sequences together, which breaks the spatial inversion symmetry of PCs. In this paper, a one-way multichannel and wide-angle absorber based on the one-dimensional superconductor photonic crystals (SPCs) in the terahertz regime is realized via splicing the classical quasi-period sequences and manipulating the ambient temperature properly, whose characteristics and mechanisms are theoretically investigated by the transfer matrix method. The preeminent absorbing features of the proposed SPCs are ascribed to the temperature and frequency-dependent refractive index of the superconductor components, whose imaginary part plays a role in giving rise to the high dissipation. Additionally, when the thickness of the whole structure is of the order of the incident electromagnetic wavelength, the one-way absorption and the reflection in the opposite direction can be perfectly obtained. The calculated results demonstrate that the relative bandwidths of the one-way effective absorption regions in our proposed SPCs can reach to 51.94%, 30.18%, and 19.12%, respectively, and the maximum angle where the wide-angle absorption region can sustain is up to 84° for TM wave by controlling the related parameters. Moreover, the impacts of the external factors such as temperature and incident angle and the interior elements including the thicknesses of diverse layers and the recursive numbers of the cascading sequences on the absorbing performance are also taken into account. To explicitly verify the reliability of our model, the impedance matching and the average refractive index are introduced for explaining the splendid multichannel absorption. As a whole, our research offers effective guidance for the theoretical excogitation of the multichannel and wide-angle absorber in the optical field. [ABSTRACT FROM AUTHOR]

• The JM is multi-function, has high quality factors, and works in THz. • The JM can realize two different logic gates on the positive and negative scales. • The JM can realize the sensing of three different physical quantities. • The JM provides a new way for the detection of human organs by angle sensing. • The JM provides a new idea for glucose and bacterium detections by RI sensing. In this paper, a Janus metastructure (JM) is given, which can realize the multi-function of different logic gates and detection of multiple physical quantities such as magnetic field, angle, and refractive index on the positive and negative scales. Furthermore, the multiscale sensing is also controlled by the logic gate. By varying the two different magnetic fields applied to the specific medium layers, the sharp absorption peak (AP), which is modulated by the external magnetic fields, is obtained in the terahertz (THz) range. The emergence of AP follows NOR logic and AND logic gates, on the positive and negative scale respectively. The results demonstrate that the frequency point (FP) of AP will fluctuate in response to the changes in the detection of physical quantities. Consequently, it is possible to accomplish physical quantities sensing functionalities by determining the FP of AP. The JM, proposed in this paper, provides a new research idea and has a more promising future. Its detection ranges of refractive index, tiny angular changes and magnetic field are 0.61 ∼ 0.65 T or 1.185 ∼ 1.2 T, 1.4 ∼ 1.9 degrees or 2.9 ∼ 3 degrees, and 1.05 ∼ 1.45 or 2.1 ∼ 2.5, which can be widely used in biomedical and physical fields. [ABSTRACT FROM AUTHOR]

• The LPS can detect four different quantities simultaneously based on a single LPS. • The LPS provides (phase/frequency) modulation detection methods based on CPA. • The LPS enables a wide detection range, high sensitivity, and little detection limit. • The LPS can be applied to pressure sensing, photosensitive sensing, and biosensing. Contrary to the traditional single-function sensor, a layered photonic structure (LPS) is proposed in this paper for multipurpose sensing based on the mechanism of coherent perfect absorption (CPA), which can simultaneously detect changes in the thickness of the dielectric layers, the refractive index, the incident angle, and the applied magnetic field intensity. Utilizing the Faraday effect of magnetized yttrium iron garnet, CPA is excited in the LPS. The transfer matrix method (TMM) is utilized to theoretically calculate the sensitivity, linear range, and figure of merit of the structures. To achieve high adaptability and a wide sensing range, the LPS provides two modulation detection methods based on CPA: phase modulation, which regulates and compensates for absorption via changing the optical phase, and frequency modulation, which utilizes the frequency band in comb-like absorption peaks. Due to the fragility of CPA, the multipurpose structure is of high precision, high-sensitivity. Furthermore, LPS benefits from its compact size and ease of fabrication. Therefore, we expect that our study will have some viable potential in the gauging arena. [ABSTRACT FROM AUTHOR]

A new novel of scatterers which is in the form of a multi-ring shape is proposed in this paper. The circular scatterers in the two-dimensional (2D) photonic crystals (PCs) have been replaced by the multi-ring ones based on the honeycomb and Kagomé lattices, and the effects of the number of layers (N), the refractive index (n), and the ring width (W) for the multi-ring scatterers on the photonic band gaps (PBGs) are also researched. After that, the relative properties of the absolute PBGs and all-angle negative refraction (AANR) phenomenon in two different types of inserted scatterers have been probed into. The band structure diagrams of those two lattices and equifrequency contours (EFCs) for two different inserted scatterers are acquired through the plane wave expansion (PWE) method. Through comparison, it is qualified for being figured out that, if the scatterer structure is varied from circular rode to multi-ring one, the bandwidths of some absolute PBGs can be expanded or the number of absolute PBGs can be added. Then, through the diagrams of EFCs and the band structures, the phenomenon that the AANR range shrank after the change has been discovered, and verify it by calculation. • A novel multi-ring structure scatterer with high symmetry is proposed. • The multi-ring structure provides multiple parameters which can be adjusted to control the PBGs for TE and TM polarization PBGs. • The introduction of multi-ring scatterers reduces the frequency range of AANR, which provides a new idea for the design of beam splitters. [ABSTRACT FROM AUTHOR]