Analysis of Reflectance Properties in 1D Photonic Crystal Containing Metamaterial and High-Temperature Superconductor

In the present work, reflectance properties of one-dimensional photonic crystal (1D PC) containing a metamaterial and high-temperature superconductor have been investigated theoretically and analyzed. The reflectance/transmittance spectrum of the proposed structure is obtained by using the characteristic or transfer-matrix method (TMM). The results show that by increasing the thickness of the metamaterial layer, the width of the second reflection band decreases while the width of the first reflection band remains almost the same though it shifts towards the higher frequency side. In addition to this, a new band gap arises in the lower side of frequency. But, when the thickness of the superconductor layer is increased, the width of both the bands increases and no additional band arises in this case. Moreover, the reflection band is also affected by varying the operating temperature of the superconducting layer and the results show that bands get narrower by increasing the operating temperature. Finally, the effect of incident angle on the reflection band has been discussed for both transverse electric (TE) and transverse magnetic (TM) polarizations.     

Investigating the Omnidirectional Photonic Band Gap in One-Dimensional Superconductor–Dielectric Photonic Crystals with a Modified Ternary Fibonacci Quasiperiodic Structure

In this paper, an omnidirectional photonic band gap (OBG) of one-dimensional (1D) superconductor–dielectric photonic crystals (SDPCs) with a modified ternary Fibonacci quasiperiodic structure which originates from Bragg gap is theoretically investigated by the transfer matrix method (TMM) in detail. The SDPCs are composed of superconductor and two kinds of homogeneous, isotropic dielectric. Such OBG is independent of the incidence angle and the polarization of electromagnetic wave (EM wave). From the numerical results, the OBG can be notably enlarged by tuning the thickness of superconductor and dielectric layers but cease to change with increasing the Fibonacci order. The OBG also can be manipulated by the ambient temperature of system. Especially, the ambient temperature of system is close to the critical temperature. However, the damping coefficient of superconductor has no effects on the OBG. The gap/midgap ratio of OBG also is studied by those parameters. It is shown that 1D SDPCs with a modified ternary Fibonacci quasiperiodic structure have a superior feature in the enhancement of OBG compared with the conventional 1D ternary and conventional ternary Fibonacci quasiperiodic SDPCs.     

Properties of Photonic Band Gaps in Superconductor Multilayer Structure with Periodically Varying Ambient Temperature

The properties of the reflectance for a superconductor multilayer structure with periodically varying ambient temperature have been theoretically investigated by the transfer matrix method (TMM). From the numerical results, it has been shown that such system has the photonic band gap (PBG) properties of photonic crystals (PCs), so it can also be called superconductor photonic crystals (SPCs). It is found that the locations and bandwidths of PBGs can be modulated by the incident angle. The frequency ranges and central frequencies of PBGs can be tuned by the temperature and thickness of superconductor layer A (higher temperature superconductor layer), respectively. The bandwidths of PBGs can be notably enlarged with increasing the temperature of superconductor layer A. The frequency ranges of PBGs can be controlled by increasing the thickness of superconductor layer A, and the more PBGs appear. The damping coefficient of superconductor and the number of periods have little effect on the bandwidths of PBGs under low-temperature conditions. It is shown that this kind of SPCs has potential applications in filters, microcavities, and fibers, etc.     

夹杂及弹性耦联对手性蜂窝复合材料吸振带隙的影响

为了研究手性蜂窝复合材料的振动特性与其振动传播带隙之间的关系,首先,建立了该种材料离散多自由度的夹杂-韧带振动力学模型,该模型考虑了其内嵌夹杂的局部振动与由微结构韧带连接的节点环之间的弹性耦联及诱发共振模态。然后,重点研究了微结构元件之间的耦联程度和微结构元件的尺寸参数对材料吸振带隙低频段和高频段的影响,并结合有限元方法对模型进行了验证分析。结果表明:除柔性包覆的夹杂以外,耦联诱发振动、节点环和韧带的材料及尺寸参数都对手性蜂窝复合材料的固有振动频率产生显著影响,从而控制带隙的位置和带宽。随着节点环内、外弹性耦联程度的减小,夹杂的模态频率将控制带隙的低频段,且随着夹杂质量的增大,低频段的频率降低;高频段由韧带振动表征;当节点环内、外弹性耦联程度增大时,带隙的低频段对韧带和框架的模态更加敏感,从而出现比夹杂模态频率更低的带隙。无论弹性耦合程度强弱,当韧带和节点环的厚度减小时,材料第三阶较高的包覆层变形频率将被相对更低的韧带振动频率取代。所得结论可为小尺寸、低频宽带隙手性蜂窝型隔振材料的设计研究提供理论指导。     

TM Wave Resonant Peaks in Defect-Free Multilayer Structures Containing Nano-Scale Y123 Superconductors

In the ultraviolet region and by using transfer matrix method, the transmission spectra of electromagnetic waves through one-dimensional quasiperiodic photonic structures consisting of high-temperature yttrium barium copper oxide (Y123) superconductor and strontium titanate (STO) dielectric layers are studied theoretically. It is shown that for TE polarization at oblique incidence two band gaps are created, while for TM polarization three band gaps are produced. The edges of both polarizations shift to higher wavelengths by increasing incident angles. Also, for angles of incidence greater than 78^°, the second gap for TM-polarized light is eliminated. It is also found that in the supposed structure the number of PBGs can be modulated by the thickness of dielectric layer, while it is nearly insensitive to the thickness of superconductor layer. Interestingly, for the incidence angles other than normal incidence the structure can exhibit some narrow resonant peaks near wavelengths where the electric permittivity of the superconductor layer changes sign. These resonant peaks are only for TM polarization and not present for TE polarization. This structure can act as a very compact polarization sensitive splitters and defect-free multichannel narrowband tunable filters.     

Enhancement of Omnidirectional Photonic Bandgaps in One-Dimensional Superconductor–Dielectric Photonic Crystals with a Staggered Structure

In this paper, the properties of the omnidirectional photonic bandgap (OBG) realized by one-dimensional (1D) photonic crystals with a staggered structure which is composed of superconductor and isotropic dielectric have been theoretically investigated by the transfer matrix method (TMM). From the numerical results, it has been shown that such OBG is insensitive to the incident angle and the polarization of electromagnetic wave (EM wave), and the frequency range and central frequency of OBG can be tuned by the ambient temperature of system, the average thickness of superconductor layer, the average thickness of dielectric layer, and staggered parameters, respectively. The bandwidth of OBG can be notably enlarged with increasing average thickness and staggered parameter of superconductor layer. Moreover, the frequency range of OBG can be narrowed with increasing the average thickness, staggered parameter of dielectric layer, and ambient temperature, respectively. The damping coefficient of superconductor layer has no effect on the bandwidth of OBG under low-temperature conditions. It is shown that 1D superconductor–dielectric photonic crystals (SDPCs) have a superior feature in the enhancement of frequency range of OBG. This kind of OBG has potential applications in filters, microcavities, and fibers, etc.     

Investigation of Transmission Properties in One-Dimensional Quasi-periodic Superconducting Photonic Crystal

This paper explores the transmission characteristics of superconducting quasi-periodic photonic crystal structure arranged in Thue-Morse and double-period sequences. We mainly focused on the cutoff frequency of transmittance spectra. The study shows that the cutoff frequency can be appreciably tuned by generation number of sequence, thicknesses of constituent layers and operating temperature. Shifting behaviour of cutoff frequency is in contrast with periodic structure on varying superconductor thickness and temperature whereas it shows opposite trend on changing the dielectric layer thickness. It is also observed that different quasi-periodic structures show distinct values of cutoff frequency and different transmission properties. This features allow to tune the cutoff frequency or band gap in the whole infrared frequency region.     

Localized Modes in Metamaterial-Dielectric Photonic Crystals with a Dielectric-Superconductor Pair Defect

Transmission coefficient and dispersion relation are calculated for a one-dimensional photonic crystal of alternating dielectric-metamaterial slabs with a dielectric-superconductor pair defect. The presence of the superconductor slab in the pair defect layer leads to a strong depletion of the TM transmission coefficient in a frequency range close to the edges of the non-Bragg gap and around the characteristic resonance frequency of the superconductor and introduces TM electromagnetic modes inside such gap. The features of the arising modes depend on the relation between the thicknesses of the layers involved in the defect and a low-frequency mode can arise from the low-frequency continuum of the bulk metamaterial modes at a non-zero in-plane wave vector.     

周期附加质量充液管路减振特性研究

以充液管路振动控制为目标研究周期附加质量的新型声子晶体管路振动传播特性。利用传递矩阵法建立周期附加质量充液管路带隙理论模型,深入分析影响带隙特性关键因素,包括附加质量尺寸、安装位置及材料阻尼。数值计算表明,声子晶体管路存在低频振动带隙可有效抑制振动传播,且设计方法简单、操作方便、减振效果明显,以期为充液管路减振设计提供新思路。     

“工”字型径向弹性超材料零频起始带隙特性研究

为了得到零频起始带隙,提出"工"字型径向弹性超材料,并研究了其不同约束状态下弹性波的传播特性。通过对色散关系,频响函数和本征模位移场计算研究,发现在双面约束状态下可产生0~16 849 Hz的零频起始宽频带隙,主要由约束作用引起的模态转变产生。进一步,通过研究有限周期结构的方向振动位移场,发现零频起始带隙产生的机制为局域共振机制。最后,分析了结构参数对零频带隙位置及带宽的影响。研究结论可以应用于超低频减振等工程领域。     

“工”字型径向弹性超材料零频起始带隙特性研究

为了得到零频起始带隙,提出"工"字型径向弹性超材料,并研究了其不同约束状态下弹性波的传播特性。通过对色散关系,频响函数和本征模位移场计算研究,发现在双面约束状态下可产生0~16 849 Hz的零频起始宽频带隙,主要由约束作用引起的模态转变产生。进一步,通过研究有限周期结构的方向振动位移场,发现零频起始带隙产生的机制为局域共振机制。最后,分析了结构参数对零频带隙位置及带宽的影响。研究结论可以应用于超低频减振等工程领域。     

YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7−<Emphasis Type="Italic">x</Emphasis></Subscript>/BaTiO<Subscript>3</Subscript> 1D Superconducting Photonic Crystal with Tunable Broadband Response in the Visible Range

Based on the transfer matrix method, we studied theoretically the transmittance of a 1D photonic crystal (PC), consisting of alternating layers of a dielectric material (BaTiO₃) and a superconductor (YBa₂Cu₃O_7?x ). The dielectric properties of this system are described by the two fluid model. We have investigated the transmittance intensity and its bandwidth dependence on the superconductor thickness, incident angle, and temperature in the PC. It was found that the electromagnetic wave propagation can be controlled to be forbidden or allowed in certain wavelengths in the visible and ultraviolet range, and the photonic band gap (PBG) width can also be tuned varying these parameters. We showed that by increasing the thickness of the superconductor layer it is possible to control the number of PBGs in the structure. Also, we found that the frequency ranges of PBGs are sensitive to the incident angle and the polarization of the electromagnetic waves; the bandwidth of PBGs can be notably enlarged by increasing the angle in the TE polarization, but narrowed in the TM one. Additionally, we found that transmission is not markedly affected by temperature variation, but small shifts in the PBGs are presented. We hope these results can be of technical use for developing potential applications in optoelectronic devices.     

Photonic and omnidirectional band gap engineering in stack of exponential graded index material and negative index material

We have investigated the photonic band gaps (PBG) and omnidirectional band gaps in one-dimensional photonic crystals made up of alternate layer of exponential graded index material and negative index material. We have considered the influence of material properties, geometrical parameters and material composition on the PBG and omnidirectional band gap. Results show that the parameters of exponential graded index material and negative index material can change the photonic and omnidirectional band structures remarkably. Number and bandwidth of PBG increases with increasing the negative index material layer thicknesses while thicknesses of graded index layer only have an effect on the bandwidth of PBGs. The bandwidth of PBG also depends on grading profile parameter of exponential graded index layers and bandwidth can be tuned with increase the value of grading profile parameter. This work can facilitate the design of filters and reflectors, and provide the basic understanding of the influence of graded index materials and metamaterials on the PBG properties.     

层状双周期结构声子晶体带隙特性研究

设计了一种层状五组元双周期结构声子晶体,并将其等效为一维声子晶体,采用传递矩阵法推导出了该结构的能带结构;在该带隙范围内弹性波或声波的传播能够得到有效抑制,实现对噪声的控制。同时,分析了取消内部周期以后第一带隙的变化以及改变硅橡胶层厚度对第一带隙的影响。结果表明,该结构与简单二元结构相比,在降低带隙频率的同时有效减轻了结构质量,且"内部周期"主要影响带隙宽度;当增加硅橡胶层的厚度时,带隙频率进一步降低。     

Omnidirectional Photonic Band Gap in One-Dimensional Ternary Superconductor-Dielectric Photonic Crystals Based on a New Thue–Morse Aperiodic Structure

In this paper, an omnidirectional photonic band gap (OBG) of one-dimensional (1D) ternary superconductor-dielectric photonic crystals (SDPCs) based on a new Thue–Mores aperiodic structure is theoretically studied by the transfer matrix method (TMM) in detail. Compared to zero- $\bar{n}$ gap or single negative (negative permittivity or negative permeability) gap, such OBG originates from Bragg gap. From the numerical results, the bandwidth and central frequency of OBG can be notably enlarged by manipulating the thicknesses of superconductor and dielectric layers but cease to change with increasing the Thue–Mores order. The OBG also can be tuned by the ambient temperature of the system especially close to the critical temperature. However, the damping coefficient of the superconductor layer has no effects on the OBG. The relative bandwidth of OBG also is investigated by the parameters as mentioned above. It is clear that such 1D ternary SDPCs have a superior feature in the enhancement of the bandwidth of OBG compared to the conventional ternary SDPCs and conventional ternary Thue–Mores aperiodic SDPCs. These results may provide theoretical instructions to design the future SDPCs devices.     

a-Si：H叠层薄膜太阳电池的最佳设计的计算机模拟

为了更好地利用太阳光谱，提高电池效率．可以在单结电池最佳设计的基础上采用叠层技术。本文对a-Si：H叠层薄膜太阳电池进行了计算机模拟，提出各层电池的禁带宽度最佳匹配以及各层电池本征层的最佳厚度的设计方案。计算表明，当单结电池效率为12．09％时，三叠层电池的效率增加至16．93％，但进一步增加电池的层数，电池效率的增加变得缓慢。另外．禁带宽度对本征层最佳厚度也有一定的依赖关系。禁带宽度越大，本征层最佳厚度也越大。     

一种基于局域共振的低频超宽带隙瓣状声学超材料

针对低频声波的衰减问题,设计了一种基于局域共振(Local Resonance,LR)机理的带瓣型结构的声学超材料,并运用COMSOL有限元软件MULTIPHYSICS 4.3计算分析了所设计的结构元胞带隙特性及其振动特性,研究表明,所设计的声学超材料比无瓣型声学超材料带隙更宽,并且仅用单层结构同种元胞组合就可以在一定频率下形成较宽的多个完全带隙,而不需要通过不同种元胞组合或是多层结构的复合而达到一定带隙特性。在此基础上,进一步对所设计的声学超材料的几何尺寸进行了优化。     

Control of the coating layer thickness of TiO2–SiO2 core–shell hybrid particles by liquid phase deposition

This paper describes control of the coating layer thickness and the crystallite size of the core–shell hybrid particles by controlling the process parameter. The core–shell hybrid particles were prepared using liquid phase deposition (LPD). We confirmed that the homogeneous coating was attained from the result of the zeta potential and the transmission electron microscope (TEM) observation. Furthermore, the coating layer microstructure was estimated using Brunauer–Emmett–Teller (BET) method. The obtained coating layer of titania was estimated using the band gap energy. Results indicate that the blue shift of the band gap energy signifies that the physical property of the hybrid particles was controlled by the coating layer thickness and the crystallite size, which are determined by the processing parameters.     

一维光子晶体的带隙特性研究

一维光子晶体是指介质只在一个方向成周期性排列的材料。利用薄膜光学的特征矩阵法研究了一维光子晶体的禁带特性,分析了填充率变化、厚度的随机扰动对光子带隙的影响。结果表明,随着填充率的变化,各能级的带隙率变化,并且存在一个极大值;厚度的随机扰动对光子带隙也有一定的影响,随机度不同,对光子带隙的影响也不一样。本研究对一维光子晶体的设计与制备有一定的参考价值。     

Theoretical modelling of one dimensional photonic crystal based optical demultiplexer

An optical demultiplexer through one-dimensional Si–SiO₂ photonic crystal structure in the presence of air cavity with a single crystal PMN-0.38PT material is presented. The transmittance of this structure is obtained using the transfer matrix method. The transmittance of this structure shows a sharp passband in the band gap region. It is observed that by introducing PMN-0.38PT layer in both sides of the air cavity, the existing band gap region of Si–SiO₂ structure is slightly increased. Here, PMN-0.38PT material is working as a tunable element for passband. By applying some external potential on PMN-0.38PT crystal, the thickness of cavity layer can be tuned and the passband can be placed at any desired wavelength in the band gap region. Since the photonic band gap region contains a range of wavelengths which are not allowed to pass through the structure can be considered as a multiplex signal for the proposed demultiplexer. Therefore, any optical signal that lies in the band gap region of the structure can be separated into its components as a pass band. Hence, the proposed structure will work as an optical demultiplexer.