Tunable Multiple Fano Resonances in One-Dimensional Photonic Crystal Containing Multiple Superconductor

We investigated the optical properties of one-dimensional photonic crystal composed of multiple different superconductor materials altogether theoretically by transfer matrix method. The number of Fano resonances generated in transmittance spectra depends on the number of different superconductor materials incorporated in the structure of photonic crystal. The Fano resonances are very sharp and sensitive to the varying parameters. The line profile of multiple Fano resonances in transmission spectra can be tuned by varying the thickness of the layers, the angle of incidence, and the temperature of superconductor photonic crystal. The tunable characteristic of multiple Fano resonances has potential application in bistable optical devices, switches, and sensors.     

Analysis of Temperature-Dependent Optical Properties in 1D Ternary Superconducting Photonic Crystal with Mirror Symmetry

The temperature dependence of the defect mode in a 1D ternary superconducting photonic crystal (PC) with mirror symmetry was theoretically investigated by simultaneously considering thermal expansion effect and thermal-optical effect. Three different materials H (high-refractive index dielectric), L (low-refractive index dielectric), and S (superconducting material) are used to construct the ternary superconducting PC structure. For comparison, six structures are discussed. It is found that the structure (HLS) ^N (SLH) ^N has the highest temperature sensitivity. Here, N is the number of periods. The average change in the central wavelength of the defect mode is 31.18 nm/K as the thickness of superconducting layer is 50 nm. Thus, based on the structure (HLS) ^N (SLH) ^N , a low temperature sensor with higher sensitivity can be designed to realize the low temperature sensor.     

Study of Defect Modes in 1d Photonic Crystal Structure Containing High and Low T c Superconductor as a Defect Layer

The present paper describes the study of defect modes in a one-dimensional photonic crystal (1d-PC) containing a high and low temperature superconductor as a defect layer at different temperatures below the superconducting transition temperature (T _c ). Since the refractive index of the superconducting material is dependent on the penetration depth, which depends on the temperature of the superconducting material, hence by changing the temperature of the superconducting material its refractive index can also be changed. Analysis of the transmission spectra of defect modes in the reflection band of 1d-PC structure shows a shift in the wavelength peak of the defect mode. The shift in peak is different for different superconducting materials and it increases with the increase in temperature whether the defect layer is high T _c or low T _c superconductors. We also study the presence two defect layers in a 1d-PC structure, one with high T _c and other with a low T _c superconductor. Further, the effect of variation in the thickness of the defect layer on the defect modes of the PC structure has also been studied In order to obtain the transmission (reflection) spectra of a 1d-PC structure with a defect, we employ the transfer matrix method (TMM). This property of the defective PC structure can be exploited in designing the temperature sensor and narrow optical filters. Further, this tunable feature of superconductor photonic crystal has technical use in the superconducting electronics and photonics.     

Filtering Properties of Photonic Crystal Dual-Channel Tunable Filter Containing Superconducting Defects

In this work, we analyze filtering properties in a photonic crystal (PC) dual-channel tunable filter. The filter structure containing twin superconducting thin films is denoted as (1/2) ^M S₁(2/1) ^N S₂(1/2) ^M . Here, 1 and 2 are dielectrics of SrTiO₃ and Al₂O₃, respectively. S₁ and S₂ are two high-temperature superconducting thin films taken to be the typical system, YBa₂Cu₃O_7?x . The two channel frequencies can be designed to locate within the photonic band gap (PBG) of the original PC (1/2) ^M . Channel frequencies can be significantly changed by changing N, the stack number of the center PC. With the use of superconducting defects, channel frequencies are temperature-dependent, that is, the filter is thermally tunable. The proposed filter structure is of technical use in superconducting photonic applications at terahertz frequency.     

Omnidirectional Reflectance of Superconductor-Dielectric Photonic Crystal in THz Frequency Range

Journal of Superconductivity and Novel Magnetism - In this paper, we analyze the omnidirectional reflection characteristics of a superconductor photonic crystal for TE and TM modes, by using the...     

Two Channel Thermally Tunable Band-Stop Filter for Wavelength Selective Switching Applications by Using 1D Ternary Superconductor Photonic Crystal

By studying temperature-dependent dispersion characteristics and group velocity of 1D ternary photonic crystal (TPC) composed of dielectric-superconductor-dielectric materials, a thermally tunable band-stop filter which is capable of stopping unique wavelength channels without causing any interference amongst equally spaced wavelength channels of full width at half maximum of 1 nm each as per the requirement of wavelength division multiplexing standards adopted by the International Telecommunication Union specifying channel spacing in terms of frequency (wavelength) is suggested. The proposed structure can efficiently work as a two-channel wavelength selective switch for wavelength division multiplexing (WDM)-based all-optical networks. This study also gives theoretical insight to design some new kind of optical memories and tunable buffers which holds data temporary and have potential applications in modern communication systems.     

Optical Properties of New Type of Superconductor-Semiconductor Metamaterial Photonic Crystals

Based on the fundamentals of the characteristic matrix method, we theoretically investigate the optical properties of onedimensional superconductor metamaterial photonic crystals. The photonic crystals are composed of a superconductor layer and two semiconductor metamaterial layers of In_0.53Ga_0.47As with different doping densities. The numerical results show negative values in permittivity of the metamaterial layer along a broad band of the incident radiation. The negative values show a significant effect on the optical properties of the present structure. Moreover, the optical properties of our design can be controlled by different parameters such as thicknesses of the layers, the operating temperature and the doping density. Our results may be suitable for different applications in the optical community.     

Investigation of Reflectance Properties in 1D Ternary Annular Photonic Crystal Containing Semiconductor and High-<Emphasis Type="Italic">T</Emphasis><Subscript><Emphasis Type="Bold">c</Emphasis></Subscript> Superconductor

In this paper, we present the theoretical investigation and study of reflectance properties in a 1D ternary annular photonic crystal (TAPC) containing a semiconductor and a high-temperature superconductor. The proposed structure consists of alternate layers of indium nitride (InN), Bi₂Sr₂CaCu₃O₈ (BSCCO), and air placed in free space. A reflectance spectrum of the TAPC is obtained by employing the transfer matrix method (TMM) in the cylindrical waves for both transverse electric (TE) and transverse magnetic (TM) polarized waves. From the study of reflectance spectra, it is observed that the reflection band of the annular photonic crystal depends on the azimuthal mode number m in addition to other parameters. It is found that for azimuthal mode number m = 0, the width of the reflection band of the annular photonic crystal is the same as that of a planar photonic crystal (PPC). When the azimuthal mode number increases, the width of the reflection band increases at higher m values (m >5) for TE waves. In the case of the TM wave, it is interesting to observe that a superpolariton gap is created for a higher value of the azimuthal number (m >0). Further, we see the effect of the starting radius (ρ ₀) on the reflection band of the TAPC structure at the given m number for both TE- and TM-polarized waves. Finally, the effect of temperature on the reflectance spectra for both TE and TM waves at the given ρ ₀ and azimuthal mode has been studied.     

Maximization of Photonic Bandgaps in Two-Dimensional Superconductor Photonic Crystals

In this paper, we investigate the properties of photonic band structures in two-dimensional superconductor photonic crystals (2D-SCPCs) using the frequency dependent plane wave expansion method. We consider two types of 2D-SCPCs, which are composed of superconductor (dielectric) rods embedded into a dielectric (superconductor) background, named type I (type II) SCPCs. We target maximization of the gap-to-mid-gap ratio by varying many parameters, namely, shape of the rods, the operating temperature, the permittivity of the dielectric material, and the threshold frequency of the superconductor. We show that the type II SCPCs have a higher gap-to-mid-gap ratio than the type I SCPCs. In addition, the PBGs can be tuned efficiently by the operating temperature. Moreover, the photonic band structures can be tailored by changing the dielectric constant of the background (rods) in the type I (type II) SCPCs.     

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.     

Transport Properties of a Single Crystal of Pressure-Induced Superconductor CePtSi2

We synthesized single crystals of pressure-induced superconductor CePtSi₂ by an In-flux method, and measured its electrical resistivity ρ under hydrostatic pressure. At ambient pressure, ρ shows two maxima at T ₁=3.7 K and T ₂=33 K, and a downward bend at the Néel temperature T _N. With increasing pressure T _N decreases and disappears above 1.11 GPa, as reported in a polycrystalline sample. On the other hand, the maximum at T ₁ becomes a shoulder above P _v=1.21 GPa, and begins to increase with increasing pressure, indicating the beginning of a valence crossover.     

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.     

The Microwave Properties of YBCO Photonic Crystal Structure Microstrip

We have fabricated three YBCO microstrip lines. One is conventional microstrip line. Two are etched periodic holes. The thickness for the microstrip lines with and without holes are 0.3 and 0.45μm, respectively. The periodic holes in the microstrip line change the microwave properties more significantly in the case of thin film than thick film. We have also fabricated YBCO photonic bandgap (PBG) microstrip circular disk filter in film with thickness 0.7,μm. The center frequency of the pass band filter is 12.23,GHz. The filter provides band width 1.6% and low insertion loss about ?0.5 d B.     

基于LiNbO3材料的可调谐光子晶体滤波特性研究

提出了含有电光材料LiNbO3的一维三元光予晶体结构,利用传输矩阵法,研究了在外电场作用下缺陷共振峰的波长可调谐滤波特性.在不改变光子晶体几何外形尺寸的情况下,通过改变施加于电光材料LiNbO3上的外电场调节其折射率,使得带隙内产生的强局域、高透射、窄宽度的缺陷共振峰发生偏移,从而实现滤波器的可调谐特性.数值模拟结果表明,在近红外波段,缺陷共振峰随外电场的增加向短波长方向线性移动;同时,在固定外电场作用下,随着入射角度的增大,光子带隙将整体向着短波长方向平移,且带隙内的缺陷共振峰随之发生同步移动.以上这些特性,可应用于近红外波段的波长可调谐滤波器件中.     

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。     

一种含Re单晶镍基合金的蠕变行为

通过组织形貌观察及蠕变曲线测定,研究了一种含Re镍基单晶合金的高温蠕变行为.结果表明,4.2％Re单晶合金在1060～1100℃温度区间具有较好的承温能力,但表现出较强的施加应力敏感性.经高温蠕变断裂后,在试样不同区域γ'相具有不同的组织形貌,在远离断口区域γ'相形成的筏状组织与施加应力轴方向垂直,而在近断口区域,筏状γ'相的粗化及扭曲程度增加为该区域发生较大塑性变形所致.在蠕变后期,合金的变形机制是迹线方向为[011]和[011]的滑移位错切入筏状γ'相,主次滑移系交替开动,使筏状γ '相发生扭折形成不规则的扭曲形态,直至发生断裂是合金的蠕变断裂机制.     

TiO2/SrTiO3光子晶体薄膜的制备及光电催化性能

以单分散聚苯乙烯(PS)微球在FTO导电玻璃表面自组装形成的蛋白石(Opal)结构为模板,使用溶胶-凝胶法进行TiO2前驱体的填充,退火后制备出反蛋白石结构的TiO2光子晶体薄膜。进一步通过水热反应将部分TiO2反应生成SrTiO3从而形成TiO2/SrTiO3异质结。通过多种手段技术表征了所制备材料和结构的晶型,形貌及其光电化学性能。研究结果表明,SrTiO3的负载量和晶粒大小可以通过水热反应时间调控。在经过0.5h的水热反应后,SrTiO3的负载量为9.6%,TiO2/SrTiO3薄膜保持了原有的光子晶体结构,且光电流增大了82%。TiO2/SrTiO3异质结构的形成能有效地促进光生载流子的分离,提高光电催化性能。     

Feasibility Assessment and Analysis of a Forward Injected Photonic Crystal Device

A forward injected photonic crystal device design has been proposed for the purpose of injecting a high carrier concentration across the intrinsic region of a p-i-n diode formed across the waveguide of a photonic crystal in order to modulate the refractive index of the waveguide and generate a highly compact optical device. A numerical model was developed and evaluated both to assess the feasibility of this particular approach and to optimize the design. Carrier concentrations as high as $5.5 times 10^{17} hbox{cm}^{-3}$ were injected across the intrinsic region of a p-i-n diode formed across the waveguide of an InP photonic crystal slab by highly forward biasing the device. This level of injection was capable of causing a negative shift in the refractive index of approximately −0.004 with response times of around 1 ns. The refractive indexes and absorption coefficients generated during this analysis were then applied to a photonic crystal waveguide in order to assess the feasibility of developing a compact optical device using a strongly forward injected p-i-n diode.      

光子晶体纤维的制备及应用

光子晶体纤维是一种具有结构色的纤维,其无需染色就具有颜色亮丽、永不褪色、色彩饱和度高等特点,符合当前绿色、环保的要求,拥有广阔的发展前景。概述了光子晶体的原理、制备方法及应用,重点探讨了光子晶体纤维的制备方法,介绍了目前研究报道的多层膜干涉、自组装、电泳沉积、静电纺丝和热压印等方法,并讨论了这些方法的优缺点。