One-dimensional Periodic Structure Research Articles

Omnidirectional Reflection Band of One-dimensional Periodic Structure (1DPS) of Si/SiO2 with Defect Mode of Nematic Liquid Crystal (5CB)

Omnidirectional Reflection Band of One-dimensional Periodic Structure (1DPS) of Si/SiO2 with Defect Mode of Nematic Liquid Crystal (5CB)

Spatially asymmetric transients of propagating exciton-polariton modes in a planar CdZnTe/CdMgTe guiding structure

We report on ultrafast time-resolved pump-probe studies in a CdZnTe/CdMgTe planar guiding structure covered with a metallic grating. The one-dimensional periodic gold structure allows for efficient coupling into the guiding layer for $p$-polarized 30 fs optical pulses with a large spectral bandwidth of about 60 nm. The resulting spectral width of optical pulses propagating inside the guiding layer corresponds to 20--30 nm. We demonstrate that the excitation of exciton-polariton modes in the guiding layer leads to a modulation of the optical response in the vicinity of the excitonic resonance. Spatially resolved pump-probe measurements show an asymmetric behavior in the optical response when the relative position of the pump and probe spots is varied on the scale of ten micrometers perpendicular to the metal ridges. This is attributed to the excitation of resonant and off-resonant exciton-polariton modes which propagate in opposite directions inside the guiding layer in accordance with their dispersion relations. Two main mechanisms are considered and evaluated, namely, Pauli blocking and excitation-induced dephasing, which are shown to be responsible for the pump-induced changes in the exciton absorption spectrum. While both of these processes lead to the generation of photoexcited carriers in the guiding layer, their impact on the optical properties (transmission and reflection) are different which leads to the asymmetric behavior of the spatially resolved transients.

A wave-based optimization approach of curved joints for improved defect detection in waveguide assemblies

A wave-based numerical approach is proposed for the detection of defects in waveguide assemblies with curved joints. Within this framework, the wave finite element (WFE) method is used. It provides an efficient numerical means for computing waves in one-dimensional periodic structures (waveguides), and assessing the reflection and transmission coefficients of waves around defects and curved joints. A so-called apparent reflection matrix of the defects, which takes into account the influence of the joints on the reflected signals recorded at some measurement point at the beginning of a waveguide assembly, is proposed. This appears to be the relevant criterion for detecting defects. As it turns out, an optimization procedure for the design of curved joints can be proposed to magnify the amplitude of the reflected signals issued from defects. Numerical experiments are carried out on 2D waveguide assemblies, with one or two curved joints which are parameterized with respect to their radius and angle of curvature. Optimized values of these parameters can be found which magnify the reflected signals issued from several kinds of defects. Time response simulations are finally undertaken to highlight the relevance of the proposed approach.

Multi-scale analysis for helically wound structures with one-dimensional periodicity

Purpose The purpose of this study is to present a multi-scale analysis methodology for calculating the effective stiffnesses and the micro stresses of helically wound structures efficiently and accurately. The helically wound structure is widely applied in ocean and civil engineering as load-bearing structures with high flexibility, such as wire ropes, umbilical cables and flexible risers. Their structures are usually composed of a number of twisted subcomponents with relatively large slender ratio and have the one-dimensional periodic characteristic in the axial direction. As the huge difference between the axial length and the cross-section size of this type of structures, the finite element modeling and theoretical analysis based on some assumption are usually unavailable leading to the reduction of computability; even the optimization design becomes infeasible. Design/methodology/approach Based on the asymptotic homogenization theory, the one-dimensional periodic helically wound structure is equivalent to the one-dimensional homogeneous beam. A novel implementation of the homogenization is derived for the analysis of the effective mechanical properties of the helically wound structure, and the tensile, bending, torsional and coupling stiffness properties of the effective beam model are obtained. On this basis, a downscaling analysis formation for the micro-component stress in the one-dimensional periodic wound structure is constructed. The stress of micro-components in the specified geometry position of the helically wound structure is obtained basing on the asymptotic homogenization theory simultaneously. Findings By comparing with the result from finite element established accurately, the established multi-scale calculation method of the one-dimensional periodic helically wound structure is verified. The influence of size effects on the macro effective performance and the micro-component stress is discussed. Originality/value This paper will provide the theoretical basis for the efficient elastoplastic analysis of the helically wound structure, even the fatigue analysis. In addition, it is necessary to point out that the axial length of the helically wound structure in the general engineering problems that such as deep-sea risers and submarine cables.

Tunable Sensing Property of 1D Periodic Structure with Defect of Liquid Crystal Sandwiched by Metallic Layers

In this paper, we have investigated the optical properties of one-dimensional periodic structure of dielectric materials with defect of liquid crystal (LC) sandwiched with two silver (Ag) layers. The transmission, reflection and absorption properties of considered periodic structure have calculated theoretically using transfer matrix method (TMM). Our study reports that the tunability of absorption defect peak of the defect periodic structure is achieved by the variation in the incident angle of electromagnetic wave. The obtained result suggests that such defect periodic structure may be used as tunable sensor and filter devices.

Study of Abnormal Group Velocities in Flexural Metamaterials

Generally, it has been known that the optical branch of a simple one-dimensional periodic structure has a negative group velocity at the first Brillouin zone due to the band-folding effect. However, the optical branch of the flexural wave in one-dimensional periodic structure doesn’t always have negative group velocity. The problem is that the condition whether the group velocity of the flexural optical branch is negative, positive or positive-negative has not been studied yet. In consequence, who try to achieve negative group velocity has suffered from trial-error process without an analytic guideline. In this paper, the analytic investigation for this abnormal behavior is carried out. In particular, we discovered that the group velocity of the optical branch in flexural metamaterials is determined by a simple condition expressed in terms of a stiffness ratio and inertia ratio of the metamaterial. To derive the analytic condition, an extended mass-spring system is used to calculate the wave dispersion relationship in flexural metamaterials. For the validation, various numerical simulations are carried out, including a dispersion curve calculation and three-dimensional wave simulation. The results studied in this paper are expected to provide new guidelines in designing flexural metamaterials to have desired wave dispersion curves.

Self-Organized, One-Dimensional Periodic Structures in a Gold Nanoparticle-Doped Nematic Liquid Crystal Composite.

Composite structures exhibiting a periodic arrangement of building blocks can be found in natural systems at different length scales. Recreating such systems in artificial composites using the principles of self-assembly has been a great challenge, especially for 1D microscale systems. Here, we present a purposely designed composite material consisting of gold nanoparticles and a nematic liquid crystal matrix that has the ability to self-create a periodic structure in the form of a one-dimensional photonic lattice through a phase separation process occurring in a confined space. Our strategy is based on the use of a thermoswitchable medium that reversibly and quickly responds to both heating and cooling. We find that the period of the structure is strongly related to the size of the confining space. We believe that our findings will allow us to not only better understand the phase separation process in multicomponent soft/colloid mixtures with useful optical properties but also improve our understanding of the precise assembly of advanced materials into one-dimensional periodic systems, with prospective applications in future photonic technologies.

Computing the complex wave and dynamic behavior of one-dimensional phononic systems using a state-space formulation

Inspired by advances in photonics, band structures have been used to investigate the wave behavior along phononic structures as well as their singular properties such as band gaps, defects and topological modes. The most commonly used method for computing band structures is the plane wave expansion, but it cannot be used to compute the forced response of a finite structure with boundary conditions and applied loads. To obtain such dynamic response, it is usually necessary to employ a full finite element model of the whole structure or spectral models that take advantage of the periodicity. This paper proposes a new spectral approach, based on a Riccati differential equation with the impedance as variable, to compute the transfer matrix of one-dimensional phononic systems with arbitrary geometric and material profiles. With this formulation, not only the complex band structure can be computed, but also the forced response. Results for ducts, rods and beams are presented and validated with the extended plane wave expansion and scaled spectral element methods. The proposed approach can also be applied to any one-dimensional periodic structures such as Levy plates, cylindrical shells and photonic systems. It can also be used to investigate with high accuracy and efficient computational cost the physical behavior of generic structures with non-slowly varying properties, gradient-index systems and cloaking devices.

Phase selection and intermittency of exciton-polariton condensates in one-dimensional periodic structures

An exciton-polariton condensate loaded in a single active miniband in a one-dimensional microcavity wire with a complex-valued periodic potential changes its state with an increase of the polariton-polariton repulsion. This effect depends on the type of the single-particle dispersion of the miniband, which can be fine tuned by the real and imaginary components of the potential. As a result, the condensate can be formed in a zero state, $\ensuremath{\pi}$ state, or mixed state of spatiotemporal intermittency, depending on the shape of the miniband, strength of interparticle interaction, and distribution of gain in the system. The change of the condensate wave function with increasing interaction takes place by proliferation of dark solitons, which are the building blocks of the new condensate phase. We show that, in general, the interacting polaritons are not condensed in the state with minimal losses, nor do they accumulate in the state with a well-defined wave vector.

Tunable optical filter based on one-dimensional periodic structure composed of SiO2 and anisotropic metamaterial (AMM) with a liquid crystal defect layer sandwiched by two SiO2

This paper reports the tunable transmission properties of asymmetric one-dimensional periodic structure (1DPS) composed of SiO2 and anisotropic metamaterial (AMM) layers with defect of liquid crystal (LC) sandwiched by two SiO2 layers, i.e., (SiO[Formula: see text]AMM)[Formula: see text]SiO[Formula: see text]LC[Formula: see text]SiO[Formula: see text](SiO[Formula: see text]AMM)3 using the transfer matrix method (TMM). We have studied the optical properties of the periodic structure (SiO[Formula: see text]AMM)3 [Formula: see text]SiO[Formula: see text]LC[Formula: see text]SiO[Formula: see text](SiO[Formula: see text]AMM)3 with a different incident angle of the electromagnetic wave for particular director angle of LC molecules. The tunability of the transmission property of the considered 1DPS shows that the transmittance depends upon the orientation of LC molecules. Such an asymmetric periodic structure (1DPS) composed of SiO2 and AMM with a defect of LC sandwiched by two SiO2 layers, (SiO2 [Formula: see text]AMM)[Formula: see text]SiO[Formula: see text]LC[Formula: see text]SiO[Formula: see text](SiO[Formula: see text]AMM)3, may be used as a tunable optical filter and bi-stable device.

Formation of controllable 1D and 2D periodic surface structures on cobalt by femtosecond double pulse laser irradiation

Controlling the surface morphology at the subwavelength scale is one of the cornerstones of modern nanophotonics. Femtosecond laser-induced surface structuring is a viable technique for the large-scale formation of nano- and microscale structures. A typical example is the formation of one-dimensional laser-induced periodic surface structures (LIPSSs), which can lead to strong modifications of optical and wetting properties of the material surface. Creating two-dimensional (2D) patterned structures, however, is a more challenging and rewarding task. Here, we demonstrate a single step method for fabricating various subwavelength structures on the cobalt (Co) surface using different laser fluences (0.12–0.24 J/cm2) and time delay (0–30 ps) between double pulses. More importantly, we can control the geometry and organization of the formed structures demonstrating spherical, triangular, rhombic, and high spatial frequency LIPSSs using two temporally delayed orthogonally polarized femtosecond laser beams. We show that the laser fluence and delay time between the two beams are the controlling parameters for realizing the different surface morphologies. We provide a numerically supported, phenomenological model to explain the formed 2D structures. Our model employs elements from both the scattered surface-wave interference and the self-organization theories that are commonly used to explain uniform surface structures.

Effective optical properties of the one-dimensional periodic structure of $$\hbox {TiO}_{{2}}$$ and $$\hbox {SiO}_{2 }$$ layers with a defect layer of nanocomposite consisting of silver nanoparticle and E7 liquid crystal

In this work, the dielectric property of a nanocomposite (NC) consisting of silver nanoparticle and E7 liquid crystal (LC) has been investigated theoretically at different temperatures. The study shows that the surface plasmon resonance (SPR) and filling fraction of the silver nanoparticle significantly change the dielectric property of the NC. To study the optical property of the defective periodic structure, the NC was considered as a defect layer in a semifinite one-dimensional periodic structure (1DPS) of $$\hbox {TiO}_{{2}}$$ and $$\hbox {SiO}_{{2}}$$ layers, i.e. ( $$\hbox {TiO}_{{2}}{\vert }\hbox {SiO}_{2})^{5}{\vert }\hbox {NC}{\vert }(\hbox {TiO}_{{2}}{\vert }\hbox {SiO}_{2})^{5}$$ . The optical properties of the 1DPS with the NC as the defect layer have been studied by the simple transfer matrix method (TMM). Moreover, the transmission and absorption characteristics of the 1DPS in the presence of silver nanoparticle in the NC have been studied with different orientations of the LC molecule.

Enhancement of absorption property of one-dimensional ternary periodic structure containing plasma based hyperbolic material for the application of microwave devices

Abstract This work reports a theoretical analysis of the absorption properties of a one-dimensional ternary periodic structure of dielectric, silicon dioxide and hyperbolic materials using well-known simple transfer matrix method (TMM). The hyperbolic material is a composite material of dielectric and plasma materials in which the optical constants of hyperbolic material have been studied by considering the effective medium theory. The relative permittivity of hyperbolic material has been studied with the variation of filling fraction and the electron collision frequency. The absorption of ternary periodic structure was studied with varying incident angle, in which the maximum absorption is found at incident angle 80°. Therefore, we have studied the absorption spectra of the considered periodic structure with variation of filling fraction, electron collision frequency, and thickness of dielectric material where the incident angle is constant at 80° for the maximum absorption. In this particular case, we have obtained the enhanced absorption spectra for ternary periodic structure in comparison to other angle of incidence at low normalized frequency. However, zero absorption for the same structure is obtained at the high normalized frequency range that exhibits a band gap. Now, the enhanced absorption of the considered structure has been studied with variation of filling fraction, electron collision frequency and thickness of dielectric material. We have obtained that the enhanced high absorption at the low microwave frequency may be used as a sensor, detector, logic gate; and the absorption band gap at the high microwave frequency range may as tunable absorber based microwave devices.

A bi-patch loaded microstrip line based 1-D periodic structure with enhanced stop bandwidth and band switching characteristics

ABSTRACTA one-dimensional periodic structure comprising of eight unit cells each having two metallic patches sandwiched between microstrip line and ground plane has been investigated. Patches bearing dissimilar dimensions present distinct reactive loads, determined by their respective areas, to generate relatively wider bandgap. Patches can be selectively connected to ground or left floating through a combination of vias and externally controlled FET switches. Dispersion analysis of the structure has been carried out to determine the propagating modes of the line for all four possible states of the unit cell. A top-down, design guide approach has been adopted with the effect of parameters determining performance attributes captured. The proposed structure acts as an all pass filter from DC to 19.5 GHz with all patches floating and exhibits stopband characteristics from 6 to 19.5 GHz with different combinations of the switches offering an overall stop bandwidth greater than 100%. The proposed structure offers tunability from no bandgap to bandgap with added advantages of band switching capability with double the number of unique reconfigurable switch patterns as compared to conventional single patch structures.

Graphene layers on semi-finite 1D asymmetric periodic structure of Si/Glass materials with defect of nematic liquid crystal for a sensor device

In this work, the effective absorption property of graphene layers on one-dimensional periodic structure (1DPS) of Si/Glass materials with nematic liquid crystal (NLC) as a defect has been studied theoretically. The graphene sheets are stuck on the one end of Si as well as Glass of the semifinite periodic structure of Si/Glass materials. Now the nematic liquid crystal (NLC) is embedded with the semifinite periodic structure of Si/Glass materials containing graphene layers. Using the transfer matrix method (TMM), the transmission and absorption behavior of graphene layers on semi-finite 1D asymmetric periodic structure of Si/Glass materials with a defect of nematic liquid crystal have been studied. Our results suggest that defect layer of nematic liquid crystal (NLC) in the semi-finite 1D asymmetric periodic structure with graphene layers (G),(Si∣Glass)m∣G∣NLC∣G∣(Si∣Glass)n with m = 3 & n = 5, may be used as sensor device due to high absorption behavior for a specific director angle of molecules of the nematic liquid crystal (NLC). Besides this, the absorption behavior of the structure for TE mode, (Si∣Glass)3∣G∣NLC∣G∣(Si∣Glass)5, is more effective in comparison to the absorption behavior of the structure for TM mode at normal incidence wave.

A regularized adaptive spatial resolution technique for fast and accurate analysis of metal–dielectric crossed gratings

The application of regularized jump points has been proposed [Khavasi and Mehrany in Opt Commun 284(13):3211–3215, 6] as an adaptive spatial resolution (ASR) technique to improve the convergence of the Fourier modal method (FMM) in the analysis of one-dimensional periodic structures. We extend this approach to obtain the optical response of metal–dielectric crossed gratings, two-dimensional periodic structures with a high-contrast permittivity distribution. A metallic grid and a slab of split-ring resonators are analyzed using the proposed ASR technique, and the results compared with those obtained using the conventional ASR technique and FMM. The results show that, by adequately choosing the discontinuity points of the dielectric function in the new coordinates, the convergence speed and accuracy of the proposed ASR technique are further increased compared with the conventional ASR technique.

Brewster effect when approaching exceptional points of degeneracy: Epsilon-near-zero behavior

We reveal that the phenomenon of full transmission without phase accumulation commonly associated with epsilon-near-zero (ENZ) materials for a plane-wave does not require vanishing of permittivity. We theoretically connect the phenomenon with condition of the Brewster effect satisfied at the edges of stop bands (so called exceptional points of degeneracy) and show that the full transmission without phase accumulation can be observed in various one-dimensional periodic structures. Particularly, exploiting the manifold of exceptional points of degeneracy in one-dimensional all-dielectric periodic lattices, we demonstrate that these structures not only offer a lossless and extremely simple, CMOS compatible alternative for some applications of ENZ media, but exhibit new properties of all-angle full transmission with zero phase delay.

Anisotropic behaviour and elastic moduli of average isotropic and anisotropic elastic media

Using matricant method elastic moduli of occasionally heterogeneous isotropic and anisotropic elastic media were received. Anisotropic behaviour and conditions for change in anisotropy of media associated with averaging of one-dimensional periodic structures was determined.

Backward Third-Harmonic Pulse Generation in a One-Dimensional PIM/NIM Structure

In this work, a set of couple-mode equations for describing a backward third harmonic generation (BTHG) in a one-dimensional periodic structure of positive-index material (PIM) layers and third-order nonlinear negative-index material (NIM) layers was analysed using multiple-scale method. Due to the negative-index phase matching and band-edge field enhancement the intensities of backward third-harmonic pulsed generated from the PIM/NIM periodic structure is increased for 100 time of those generated from a single NIM medium.

A tunable broadband filter of ternary photonic crystal containing plasma and superconducting material

This work reports the optical properties of a one-dimensional (1D) ternary periodic structure composed of a dielectric, magnetized cold plasma (MCP) and superconducting material by using well-known simple transfer matrix method. The MCP has considered right-hand and left-hand polarizations having positive (+ B) and negative (− B) transverse magnetic field, respectively. The transmittance of the ternary photonic crystals is analyzed by varying the angle of incidence, the magnetic field, the electron density of the magnetized cold plasma, the temperature of the superconductor, the thickness of magnetized cold plasma and superconducting material for the right-hand and left-hand polarization structures. The transmittance of the ternary photonic crystal containing dielectric, magnetized cold plasma and superconducting material has tunable broadband and narrowband filters for the left-hand and right-hand polarizations, respectively. The magnetized cold plasma layer in the ternary photonic crystal also played an important role to form the tunable gap due to the transverse magnetic field. The analysis of the transmittance of the ternary photonic crystal containing dielectric, magnetized cold plasma and superconducting materials has shown an innovative idea for the formation of the tunable broadband and the narrowband filters.