光子晶体光纤的研究与进展

光子晶体光纤是90年代发展起来的新型光波导材料,具有十分重要的研究和应用价值.本文综述了光子晶体光纤的特征和传输机理、光子晶体光纤的研究类型、制备工艺,并进一步介绍了光子晶体光纤的几个重要用途.     

光子晶体及SiO2光子晶体的制备技术

光子晶体是一种具有光子带隙的周期性电介质结构,落在光子带隙中的光将不能传播。由于其独特的调节光子传播状态的功能,成为实现光通讯和光子计算机的基础。SiO2胶体球作为胶体光子晶体的组成基元,具有广阔的应用前景。本文介绍了光子晶体的概念、特征与应用领域,以及SiO2光子晶体的制备技术。     

光子晶体传感器研究进展

部分生物体呈现的颜色具有与角度有关,不易褪色的特点。光子晶体是一种介电常数随空间周期性变化的新型光学微结构材料,其最根本特征是具有光子禁带。本文介绍了光子晶体的结构性能特点及自组装制备方法如模板法、刻蚀法等。也重点阐述了光子晶体在光、电、力、热及化学物质检测方面的应用,体现了光子晶体在传感器应用上的优势。文末对光子晶体今后的研究方向做了展望。     

基于聚合物的一维光子晶体研究进展

从一维光子晶体组装材料角度出发,总结分析了基于聚合物的有机/有机型和有机/无机杂化型一维光子晶体的结构特点、组装原理和方法、性能及应用。在有机/有机型一维光子晶体中,主要介绍了含有不同亲疏水链段的嵌段共聚物和含有可聚合双键的表面活性剂自组装形成的一维光子晶体。在有机/无机杂化型一维光子晶体中,既论述了基于聚合物、无机材料直接交替组装形成的多层膜,也讨论了基于两种无机材料组装,然后再填充柔性聚合物的一维光子晶体。通过对以上两类光子晶体材料的总结分析可知,基于聚合物材料制备的一维光子晶体可以实现多种功能,在柔性传感器、柔性光电器件、光子晶体纸、电子皮肤、3D打印等方面具有良好的应用前景。但目前基于聚合物的一维光子晶体存在组装均匀性有待提高、组装面积较小等问题,如何大规模制备均匀的功能性一维光子晶体是重要的研究方向,也是影响其实际应用的关键。     

光子晶体光局域效应提高TiO_2吸光率的应用及规律研究进展

半导体TiO_2只能吸收波长小于387 nm的紫外光,实际应用受到限制,近年来出现的新型材料——光子晶体在提高光吸收率方面引起研究者的兴趣。综述利用光子晶体提高TiO_2光吸收率的研究进展,重点阐述光子晶体在太阳能电池、光催化降解有机物和光解水制氢领域的应用,介绍当前探究光子晶体提高光吸收率的规律。总体来说,光子晶体提高光收率效果显著,但对其规律的认识不足,了解光子晶体的应用进展和规律研究现状,对高效光催化剂的制备具有重要意义。     

理化所光子晶体电浸润性研究取得新进展

正在国家自然科学基金委和中国科学院的大力支持下,中科院理化技术研究所仿生材料与界面科学院重点实验室的科研人员在具有超浸润性光子晶体的制备及应用方面取得系列进展。研究人员考察了基底浸润性对光子晶体组装单元—乳胶粒的形貌及其分子组装形式的影响;利用界面特殊的浸润性调控,实现了具有特殊光功能的花形及面包形的各向异性结构光子晶体制备;结合超亲水基材及超疏水模板形成的三明治限域作用,制备得到具有良好光波导行为的光子晶体微阵列;设计具有梯度浸润性的聚离子液体     

全光法制作三维光子晶体的研究进展

三维光子晶体作为一种新型材料已经得到了广泛的应用。用全光法制备三维光子晶体具有容易实现、成本低廉等优点。本文介绍了用光学方法制备三维光子晶体的几种方法。     

化学所利用低黏附超疏水基材制备窄带隙聚合物光子晶体研究取得新进展

光子晶体以其特殊的周期结构和可以对光子传播进行调控的特性被称为“光学半导体”,被认为是未来光子工业的材料基础。近年来,光子晶体的结构、制备和光学特性研究受到全球范围内的高度关注,并在各类光学器件、光导纤维通讯和光子计算等领域呈现广阔的应用前景。在国家自然科学基金委、科技部和中国科学院的支持下,化学所有机固体和新材料实验室的科研人员针对目前光子晶体制备和应用开展了广泛研究。他们通过结构设计,制备了具有硬核一软壳结构的乳胶粒,制备了具有特殊紧密堆积结构的高强度光子晶体。     

混合烧结法在玻璃陶瓷制备中的应用

概述了混合烧结法的分类、致密化机理、影响因素和在玻璃陶瓷制备中的应用.和传统玻璃陶瓷制备工艺相比,混合烧结法的特点在于玻璃陶瓷中的晶体是直接加入或是通过外加晶体和玻璃反应析出而不是从母相玻璃中直接析出,因而对母相玻璃组分要求不十分严格,在直接利用废玻璃制备玻璃陶瓷和复相玻璃陶瓷方面有着独特的优势.本文重点介绍了近年来该工艺在这方面的应用和进展.     

Lu2O3-SiO2体系闪烁体材料研究进展

闪烁体材料是一类吸收X-射线或α,β-射线等高能光子后发出可见光的光功能材料,在高能物理、核医学、地质勘探等领域应用广泛.综述了Lu2O3-SiO2体系闪烁体材料的最新研究进展,包括闪烁晶体、闪烁陶瓷、闪烁粉体和闪烁薄膜的研究现状,并对Lu2O3-SiO2体系闪烁体材料的应用和发展进行了总结.     

光子晶体增强三线态-三线态弱光上转换发光特性研究

基于三线态-三线态湮灭机制的长波激发短波发射的弱光频率上转换,由于所需激发光能量接近太阳光强度,在太阳能电池、光催化降解和生物成像等领域显现诱人应用前景。本文采用无皂乳液聚合法制备纳米尺寸的聚苯乙烯-甲基丙烯酸甲酯-丙烯酸(P(St-MMA-AA))单分散乳胶微球,通过控制表面活性剂用量来调控乳胶微球尺寸大小,并利用竖直沉积法制备获得与上转换发光体系匹配的光子晶体薄膜。研究表明,该光子晶体可有效增强双组份体系的上转换发光。为弱光上转换技术走向应用探索一条新途径。     

Design of photonic crystals for light-emitting diodes

Photonic crystals (PCs) can greatly enhance the optoelectronic performance of light-emitting diodes (LEDs) due to their distinctive color, photonic band gap, etc. Therefore, many scholars have conducted extensive research based on the high light extraction efficiency, good monochromaticity, and other excellent optoelectronic properties of PC LEDs. This review discusses the main principles of photonic crystals to improve the optoelectronic performance of LEDs and summarizes 12 structural applications of photonic crystal LEDs, such as PC slabs, Bragg grating, backside reflectors, surface PC, embedded PC, dual PC, PC beads, CPC, PC thin films, LIPC, defective PC, and composite architectures with other materials that boost LED optoelectronic qualities. In summary, it is found that photonic crystals can not only greatly improve the light extraction efficiency of LEDs but also improve other optoelectronic properties such as luminescent color and directional radiation angle, and reduce the manufacturing cost of LEDs. Photonic crystal LEDs are expected to be a strong candidate for future lighting technology. Finally, the prospects and challenges of PC LEDs are summarized.     

Magnetic assembly route to colloidal responsive photonic nanostructures

Responsive photonic structures can respond to external stimuli by transmitting optical signals. Because of their important technological applications such as color signage and displays, biological and chemical sensors, security devices, ink and paints, military camouflage, and various optoelectronic devices, researchers have focused on developing these functional materials. Conventionally, self-assembled colloidal crystals containing periodically arranged dielectric materials have served as the predominant starting frameworks. Stimulus-responsive materials are incorporated into the periodic structures either as the initial building blocks or as the surrounding matrix so that the photonic properties can be tuned. Although researchers have proposed various versions of responsive photonic structures, the low efficiency of fabrication through self-assembly, narrow tunability, slow responses to the external stimuli, incomplete reversibility, and the challenge of integrating them into existing photonic devices have limited their practical application. In this Account, we describe how magnetic fields can guide the assembly of superparamagnetic colloidal building blocks into periodically arranged particle arrays and how the photonic properties of the resulting structures can be reversibly tuned by manipulating the external magnetic fields. The application of the external magnetic field instantly induces a strong magnetic dipole-dipole interparticle attraction within the dispersion of superparamagnetic particles, which creates one-dimensional chains that each contains a string of particles. The balance between the magnetic attraction and the interparticle repulsions, such as the electrostatic force, defines the interparticle separation. By employing uniform superparamagnetic particles of appropriate sizes and surface charges, we can create one-dimensional periodicity, which leads to strong optical diffraction. Acting remotely over a large distance, magnetic forces drove the rapid formation of colloidal photonic arrays with a wide range of interparticle spacing. They also allowed instant tuning of the photonic properties because they manipulated the interparticle force balance, which changed the orientation of the colloidal assemblies or their periodicity. This magnetically responsive photonic system provides a new platform for chromatic applications: these colloidal particles assemble instantly into ordered arrays with widely, rapidly, and reversibly tunable structural colors, which can be easily and rapidly fixed in a curable polymer matrix. Based on these unique features, we demonstrated many applications of this system, such as structural color printing, the fabrication of anticounterfeiting devices, switchable signage, and field-responsive color displays. We also extended this idea to rapidly organize uniform nonmagnetic building blocks into photonic structures. Using a stable ferrofluid of highly charged magnetic nanoparticles, we created virtual magnetic moments inside the nonmagnetic particles. This "magnetic hole" strategy greatly broadens the scope of the magnetic assembly approach to the fabrication of tunable photonic structures from various dielectric materials.     

Recent advances in polymer colloidal crystal lasers

Colloids with a size in the nanometres to micrometres range are frequently used in both fundamental research and industrial applications. In this context, colloidal crystals (CCs)-3D ordered arrays of monodispersed colloidal microparticles with a diameter of several hundred nanometres-have garnered a great deal of attention in the intriguing research realm of photonic crystals (PCs) due to the feasible and high-throughput 3D-PC fabrication with CCs. For optoelectronic applications, it is of prime importance to construct 3D-PCs with photonic band-gaps (PBGs) in the visible wavelength range. With regard to photonic device applications, many reports have been made on a wide variety of optical reflection sensors and displays using CCs that shift the visible PBG wavelength in response to external stimuli. This Minireview describes the research progress in the investigation of CCs and their laser applications. We highlight not only the research background of CCs as 3D-PCs, but also new potential applications of CCs as flexible and widely tunable lasers by low-threshold optical excitation.     

A facile method of shielding from UV damage by polymer photonic crystals

BACKGROUND: UV radiation is a potent and ubiquitous carcinogen, which is responsible for most of the skin cancer in the human population. General UV protection materials may produce dangerous degradation products under UV irradiation; therefore, safe, nontoxic and simple UV protection approaches are urgent requirements. RESULTS: A series of photonic crystals with stopband covering the range 200–400 nm have been fabricated which can shield radiation from the whole UV range. Both UV‐visible and ¹H NMR results confirm the effective protection from UV light of 254 nm. CONCLUSIONS: A facile method for UV protection has been demonstrated by utilizing the unusual optical properties of photonic crystals that can inhibit light propagation at a given frequency without specific requirement of chemical composition. This approach opens a new way to protect from UV damage using safe materials, which is of great significance for extending the practical applications of photonic crystals. Copyright © 2007 Society of Chemical Industry     

Visible Frequency Thin Film Photonic Crystals from Colloidal Systems of Nanocrystalline Titania and Polystyrene Microspheres

This work describes a simple and novel ceramic processing technique to form periodic ordered structures in ceramic materials with a uniform pore size distribution. This material shows photonic gaps at visible/near-IR wavelengths. Monodisperse colloidal polystyrene microspheres are self-organized into a crystalline structure of close-packed spheres in a suspension of nanocrystalline titania. The nanoparticle titania fills the intersphere region simultaneously during colloidal crystallization. Removal of the polystyrene microspheres by calcination at a temperature of 520°C results in a periodic porous structure with a high refractive index background material. Crystals having ordered regions, a few millimeters across with typical grain sizes of 50–70 μm, are grown as thin films on substrates including glass and silicon. Optical reflectivity measurements indicate peaks at the stop band wavelengths that scale with the pore size. Visual inspection and optical microscopy reveal uniform colored regions for crystals with periodicity comparable to visible wavelengths. Despite the presence of cracks resulting from drying and heat treatment as well as numerous grain boundaries, optical characterization clearly demonstrates a photonic band gap. Reflectance peaks due to a pseudogap can be shifted by application of high pressure. In the following sections we will describe the experimental procedure and discuss optical reflectance and transmission measurements that can reveal information about the crystals, namely, the lattice constant, the refractive index, and the filling fraction of the background material.     

Enhanced Visible Light Absorption in a Photocatalytic Thin Film from a Decoupled Photonic Crystal

The optical and photocatalytic properties of a photonic crystal structure were examined to elucidate the origin of the enhanced visible light absorption from semiconductor photonic crystals. Both an enhancement in visible light absorption and an increase of the photoactivity of the semiconductor photocatalyst were found when a photonic crystal layer was decoupled from the photocatalytic film. The decoupling clearly shows that the optical enhancement arose from the dielectric mirror effect of the photonic crystal. As such, the enhancement was maximized by matching the high light absorbance region of photocatalytic semiconductors with the characteristic photonic band gap of the decoupled photonic crystal layer under various illumination conditions. For enhanced visible light photocatalytic activity, the decoupled photonic crystal layer does not have to be made from the same light-harvesting materials, but can be synthesized by a wide range of materials for ease of the fabrication process.