一维三元异质结构光子晶体反射特性

利用传输矩阵法对一维三元光子晶体异质结构的光学特性进行了研究,讨论了介质层厚无序度对三元结构光子禁带的影响.研究表明,将具有相互交叠光子禁带的一维光子晶体叠加构成异质结,可以有效地增大全角度反射的频率范围,当入射角从0°增大到89°,该结构均可实现从0.410 w/w0到0.654 w/w0宽频波段的全反射;相对于二元结构,三元结构可以减小在实际制作过程中随机误差引起的介质层厚无序对光子带隙的影响.该研究结果可为实现可见光及红外光波段大角度反射器的制备及应用提供理论支持.     

基于光子晶体异质结的高效太阳能电池反射器研究

设计了一种可用于太阳能电池反射器的二维三角晶格光子晶体异质结结构.采用传输矩阵法对该结构在可见至近红外波长范围入射电磁波的反射率进行了模拟计算,并比较了不同入射方向下反射率的变化.结果表明,光线垂直入射时,该结构光子晶体对近红外波段入射光可实现完全反射;随着偏转角度的增大,在整个可见-近红外波段均显示出极高的反射特性.该结构有望用于制作覆盖整个可见光-近红外波段的高效全方位反射器.     

基于光子晶体异质结的高效太阳能电池反射器研究

设计了一种可用于太阳能电池反射器的二维三角晶格光子晶体异质结结构.采用传输矩阵法对该结构在可见至近红外波长范围入射电磁波的反射率进行了模拟计算,并比较了不同入射方向下反射率的变化.结果表明,光线垂直入射时,该结构光子晶体对近红外波段入射光可实现完全反射|随着偏转角度的增大,在整个可见-近红外波段均显示出极高的反射特性.该结构有望用于制作覆盖整个可见光-近红外波段的高效全方位反射器.     

用于可见光区的薄膜光子晶体全角度反射器

采用角域叠加方法可以有效地获得可见光区域的一维光子晶体全角度反射器. 4个TiO₂ /SiO₂薄膜光子晶体用角域叠加形成全角度反射的相对带宽为4133%, 而在同样条 件下用常规的频域叠加方法合成的全角度反射的相对带宽仅为1426%. 阐述了角域叠加的 基本原理，计算给出了可见光区域的全角度反射器，并提出用角域叠加方法可方便地构建频 域叠加所无法实现的紫外区域的全角度反射器. 关键词： 薄膜光子晶体 可见光区域 全角度反射器 角域叠加方法     

含超导材料Thue-Morse序列一维光子晶体传输特性研究

超导光子晶体是一类重要的带隙可调谐的光子晶体.利用传输矩阵法研究了含超导材料的Thue -Morse序列准周期结构—维光子晶体在可见光波段的传输特性.数值结果表明在正入射时,光子带隙宽度和位置基本不随序列项数的增加而改变;准周期超导光子晶体的传输特性可以通过改变传统电介质材料的结构参数和环境温度等来进行调节.     

太赫兹无线通信系统中的反射器研究

采用传输矩阵方法和菲涅尔公式,根据THz频段不同区域内材料折射率的特点,计算模拟了聚合体聚偏氟乙烯（polyvinylidene fluoride,PVDF）/聚碳酸酯（polycarbonate,PC）一维光子晶体对THz波的反射作用.结果表明这种反射器在亚太赫兹频段具有较好的反射性能和较大的反射带宽.此外,根据计算结果,本文还对THz反射器的理论研究和设计进行了讨论. 关键词： 太赫兹反射器 太赫兹无线通信 一维光子晶体     

一维光子晶体的透射谱特性

利用传输矩阵法研究了一维光子晶体的透射谱特性,数值模拟得到了可见光波段一维光子晶体中的透射谱特性,计算结果表明可见光波段入射波长变化时,透射谱禁带宽度发生变化。研究结果为可见光波段一维光子晶体器件的设计提供了理论依据。     

硅基薄膜太阳电池一维光子晶体背反射器的模拟设计与制备

从模拟和实验两个方面研究了一种适用于硅基薄膜太阳电池的一维光子晶体新型背反射器.首先采用时域有限差分方法,模拟研究了组成一维光子晶体的两种介质的折射率比、厚度比以及周期厚度对光子禁带的影响.基于模拟结果,制备出一种由低折射率SiOx层与高折射率非晶硅a-Si层周期性交叠构成的禁带可调式一维光子晶体背反射器.通过改变a-Si层的厚度,使得禁带范围由500—750 nm波长范围红移至650—1100 nm,反射率分别达到96.4%和99%.将上述结构的一维光子晶体作为背反射器分别应用于非晶硅单结太阳电池和非晶硅/微晶硅双结叠层太阳电池,与没有背反射结构电池相比,短路电流密度分别提升了18.3%和15.2%.同时模拟研究了在不同入射角度下自然光、TE波和TM波对光子晶体反射特性的影响.研究结果表明,在太阳电池中,光线倾斜入射对一维光子晶体反射率的影响有限.     

一维电介质-金属光子晶体的光学特性研究

利用传输矩阵方法,研究了一维电介质-金属光子晶体的光学特性,该光子晶体通过在Si/SiO₂组成的电介质型光子晶体中插入一定厚度Al层形成。计算结果表明,金属层的引入可以有效提高反射效率,[Si(46 nm)/SiO₂(60 nm)/Al(10 nm)/SiO₂(60 nm)]5结构的单位周期传输衰减从[Si(46 nm)/SiO₂(120 nm)]5的7.2 dB增大到了20 dB;可以得到更宽频率范围的全方向反射带隙,例如[Si(46 nm)/SiO₂(60 nm)/Al(30 nm)/SiO₂(60 nm)]5结构即可提供550 nm带宽的全方向反射;同时讨论了金属吸收、金属层厚度及插入位置对其光学特性的影响。这种电介质-金属光子晶体有望作为性能优异的光学反射镜得到应用。     

混合准周期异质结构的带隙补偿与展宽

基于一维光子晶体异质结构的多帯隙交叠补偿思想,提出了一种新颖的混合准周期级联结构,用于扩大全方位光子带隙.该全方位反射器结构由Fibonacci准周期结构和Thue-Morse准周期结构级联构成,研究表明,相比单种准周期结构,其全方位光子带隙宽度有显著提高.系统研究了结构参数(如周期数、阶数、介质折射率和厚度)对该结构光子带隙的影响,通过与周期结构带隙特性的比较,分析了准周期结构易于实现多带隙交叠的原因,为更复杂带隙结构的补偿和展宽奠定了设计基础.     

Analysis and optimization of a new photonic crystal filters in near ultraviolet band

Transmission characteristics of one-dimensional (1D) photonic crystals (PCs) heterostructures containing defective are studied using the transfer matrix method. The key is to search the best combination style for different 1D PCs to form heterostructures. It is shown that the non-transmission range over near ultraviolet and visible range can be substantially enlarged and the phenomenon of narrow band PC filter in near ultraviolet can be realized by adjusting the repeat cycle counts of various photonic crystals. The theoretical results on multiple heterostructures containing TiO₂/SiO₂ multilayer films are presented. With a perfect omni-directional and high peak transmission filters for TE modes, this structure opens a promising way to fabricate ultra-narrow band PC filters with wide non-transmission range in near ultraviolet and visible range.     

Design of broad omnidirectional total reflectors based on one-dimensional dielectric and magnetic photonic crystals

Omnidirectional total reflectors based on one-dimensional dielectric and magnetic photonic crystals are investigated in this paper. We adopt the transmission matrix method to analyze the transmission properties of such reflectors and use the decimal genetic algorithm to obtain broad omnidirectional total reflection (ODTR) bandwidth. Finally, an omnidirectional total reflector with very broad ODTR bandwidth of 1.34ω₀ is achieved.     

Polarization- and direction-independent defect modes in a wide incident-angle range within Bragg gaps by photonic heterostructures containing negative-index materials

We propose a type of photonic heterostructure by combining dielectric one-dimensional (1D) defective photonic crystals (PCs) and magnetic 1D defective PCs. Both of the two PCs consist of alternating positive-index-material (PIM) layers with a negative-index-material (NIM) defect layer. It is demonstrated by transfer matrix method that there is a polarization- and direction-independent defect mode in a wide incident-angle range within Bragg gaps in the heterostructure. The field distributions prove that the dielectric 1D defective PC benefits to achieve the approximately omnidirectional defect mode for TE waves while the magnetic 1D defective PC benefits for TM waves. Such a structure is useful for designing polarization-independent and omnidirectional or large incident angle narrow-passband filters in optical devices.     

Omnidirectional reflector using one-dimensional dispersive photonic heterostructure

We present theoretical design for omnidirectional reflector (ODR) using one-dimensional photonic heterostructure. With the help of transfer matrix approach, we present a simple design to achieve the ODR at a desired wavelength range of interest using a high refractive index material which is dispersive at that wavelength range. Taking material combinations of SiO₂ and GaSb as low and high index medium a perfect ODR is designed in the 1480–1680 nm wavelength region.     

Dielectric omnidirectional visible reflector

We demonstrate the fabrication of an all-dielectric omnidirectional mirror for visible frequencies. The dielectric reflector consists of a stack of 19 alternating layers of tin (IV) sulfide and silica. Using a combination of thermal evaporation (for tin sulfide) and thick electron-beam evaporation (for silica), we have achieved a refractive-index contrast of 2.6/1.46 , one of the highest refractive-index contrasts demonstrated in one-dimensional photonic bandgap systems designed for the visible frequency range. The tin sulfide-silica material system developed allowed the formation of a broadband visible reflector with an omnidirectional range greater than 10%. Possible applications of the system include efficient reflectors, high-frequency waveguides for communications and power delivery, and high- Q cavities.     

Transmission properties of one-dimensional graded photonic crystals and enlargement of omnidirectional negligible transmission gap

We investigate numerically the transmission properties of one-dimensional (1D) graded photonic crystals (PCs) in detail. Under the condition of linearly graded structures, the gap broadening of three cases is calculated: the case when the thickness of low index layer is increased, the case when the thickness of high index layer is increased and the case when the thickness values of both layers are increased simultaneously. Then the gap broadening of another graded case with the thickness exponentially increased is presented. At last the enlargement of omnidirectional negligible transmission band gap is obtained.     

Omnidirectional reflection from the one-dimensional photonic crystal containing anisotropic left-handed material

We study the transmission properties in the one-dimensional photonic crystal containing alternate anisotropic left-handed material (LHM) layers and regular isotropic right-handed material (RHM) layers. For such an anisotropic case, the dispersion relation from the Bloch theorem is derived and the Bragg gaps of the periodic structure are observed. It is found that in the m=0 Bragg gap, there is an omnidirectionally reflectional (ODR) region, which is also invariant with a change of scale length, similar with the [`(n)]=0\bar{n}=0 gap in isotropic one-dimensional photonic crystal. With the aid of effective medium theory (EMT), the analytic expressions of all six elements of the effective electric permittivity tensor and magnetic permeability tensor are obtained. By using these results, we investigate the ODR region in the m=0 Bragg gap in all the possible cases of both TE and TM modes. We find that with different choices of parameters, the m=0 Bragg gap has different transmission properties, and the ODR region in it changes, consequently. The edges of the ODR region are given out in these cases. To one's interest, these results predict a complete reflection region in the m=0 Bragg gap, which is able to omnidirectionally reflect waves in both TE and TM modes.     

<Emphasis Type="BoldItalic">λ</Emphasis> /4 rule used for designing large high-reflectance region in 2D and 3D photonic crystals

Based on a series of numerical results calculated by the transfer-matrix method, we find that the /4 rule for one-dimensional (1D) optical films is also valid for 2D and 3D photonic crystals (PCs) in designing a large high-reflectance region (HRR), if the 1D counterpart approximation is used for them. A detailed process of the 1D counterpart approximation is described. The results of the 1D counterparts of real 2D and 3D PCs are in good agreement with the /4 rule. Therefore, the /4 rule can be extended to 2D and 3D structures for designing large HRRs. PACS 42.70.Qs; 42.25.Bs     

利用一维电介质和磁光子晶体设计宽带全方向全反镜

研究了基于一维电介质-磁光子晶体的全方向全反射镜（简称全反镜）。利用传输矩阵法分析了全反镜的传输特性。为了获得宽频带全反镜,利用十进制遗传算法优化全反镜的结构参数,即层厚度系数与周期数。设计过程逐步详细阐述。计算结果指出,随着参加优化的变量（厚度系数和周期数）数增多,全反带更宽,薄膜层数更少、结构总厚度更薄。最后得到了一个宽带全反镜 (0.255A0.255B)5(0.169A0.066B)8,其带宽可达1.34ω0,而薄膜层数大幅降为26层,总厚度仅为1.8634λ0,结构也非常简单。     

基于含单负材料光量子阱结构的全向多通道滤波器

分析了含单负材料的光量子阱结构中的振荡透射模的性质.用两种单负（负介电常量或负磁导率）材料交替周期堆叠形成的两个光子晶体构造了一维光量子阱结构,该结构中仅其中一个光子晶体含有零有效位相带隙.数值计算结果发现,在零有效位相带隙内存在振荡透射模.通过改变井区域光子晶体内单负材料层的厚度及周期数,振荡透射模的数目、频率及频率间隔均可调节.振荡透射模对入射角度的依赖均很弱;随着入射角度的改变,缺陷模频率的相对改变量保持在0.02以下.该研究结果可用于设计多通道全向滤波器.