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1.
首先运用Stober溶胶凝胶法制备单分散Si02球形颗粒,通过扫描电镜研究各种反应条件如氨水浓度、无水乙醇的量、TEOS的浓度、温度等对二氧化硅的颗粒大小和形貌的影响,并通过SEM对样品的表面形貌进行了表征。通过研究改变垂直沉积法的各种条件对组装成的Si02光子晶体的带隙特性的影响。分析微球粒径、悬浮液中微球的体积分数、基片与液面之间所成的角度对光子晶体带隙性能的影响,并总结了较佳的垂直沉积法条件。 相似文献
2.
光子晶体是一种周期性电介质材料,具有光子带隙和光子局域等一系列优异的光学特性。制备了多种不同直径的单分散二氧化硅胶体微球,采用垂直沉积法将不同直径,以及同一直径不同浓度的二氧化硅胶体微球自组装成多种光子晶体薄膜,并用扫描电子显微镜和紫外—可见—近红外分光光度计对其微观结构和光学特性进行了表征,结果表明所得晶体薄膜具有三维有序结构,其表面存点、线缺陷。自组装得到的光子晶体薄膜存在明显的光子带隙特征,带隙位置与二氧化硅胶体微球直径有关,带隙中心波长与理论值一致。随着二氧化硅胶体微球浓度的增加,光子带隙深度增加,特性更好,但是,当浓度大于10%时,光子带隙的深度反而减小。 相似文献
3.
利用乳液聚合方法制备了粒径约为262 nm的单分散聚苯乙烯(PS)微球。通过控制溶剂蒸发温度和液体表面下降的速度,用垂直沉积法较快速地制备出了在较大范围呈现很好有序性的密排结构聚苯乙烯胶体光子晶体,其在626 nm波长处存在光子带隙。在扫描电子显微镜(SEM)下,观察到该胶体光子晶体是面心立方(fcc)密排结构。实验结果表明,对于粒径为262 nm的聚苯乙烯微球,在温度为55℃,质量分数为0.3%的情况下,当液体表面下降的速度约为每天3 mm时,可以得到高质量的胶体光子晶体。这种高质量的胶体光子晶体可以为利用模板技术制备具有完全带隙的有序孔结构提供较理想的模板。 相似文献
4.
A fast and highly controllable method of fabricating large films of photonic crystals of colloids is reported. A charge‐stabilized colloidal suspension was run in a flat capillary driven by a pressure‐regulated air pulse. The colloidal crystal texture formed in the capillary was a sensitive function of air pressure. Above a critical pressure, the entire capillary was filled with a uniform single‐domain texture whose transmittance spectrum showed a high quality as a photonic crystal, i.e., excellent opacity at a photonic bandgap and high transparency at other wavelengths. The present method is easily applicable to industrial processes for mass production. 相似文献
5.
采用溶剂蒸发对流自组装法将单分散二氧化硅(SiO2)微球组装形成三维有序胶体晶体模板。以锗烷(GeH4)为先驱体气,用等离子增强化学气相沉积法向胶体晶体的空隙中填充高折射率材料Ge。酸洗去除二氧化硅微球,得到Ge反蛋白石三维光子晶体。通过扫描电镜、X射线衍射仪和傅立叶变换显微红外光谱仪对锗反蛋白石的形貌、成分和光学性能进行了表征。结果表明:Ge在SiO2微球空隙内填充致密均匀,得到的锗为多晶态,锗反蛋白石为三维有序多孔结构。锗反蛋白石的测试光谱图有明显的光学反射峰,表现出光子带隙效应。测试的完全光子带隙位于中红外3.4µm处,测试的光学性能与理论计算基本吻合。 相似文献
6.
报道了一种利用直径为286nm的单分散SiO2胶体颗粒制备胶体晶体的方法。乙醇悬浮中的SiO2颗粒通过毛细作用力在垂直插入其中的GaAs衬底表面自组装成胶体晶体。扫描电子显微镜(SEM)和紫外-可见分光光度计对胶体晶体的形貌和光学特性进行了表征。结果显示,所得到的胶体晶体膜具有较好的三维有序结构。分析了退火对样品光子带隙的影响。 相似文献
7.
Photo‐tunable photonic crystals were prepared from three dimensional (3D) colloidal crystal templates using a photoresponsive azopolymer. For the preparation of azopolymer infiltrated photonic crystals, silica colloidal crystals were fabricated by gravity sedimentation, a self‐assembly technique. The interstitial voids between colloidal particles were filled with azopolymer and azopolymer inverse opals were produced by treatment with aqueous hydrofluoric acid. These photonic crystals exhibited stop bands in their transmission spectra measured in the normal incidence to the (111) plane of face centered cubic (fcc). The photonic bandgap of the azopolymer infiltrated opal and inverse opal could be controlled by the refractive index change due to the photoinduced orientation of azobenzene chromophores. When the azopolymer photonic crystals were irradiated with linearly polarized light, their bandgap positions were shifted to shorter wavelength regions with increasing irradiation time. This behavior experimentally produced a photoinduced orientation of the azobenzene groups in parallel with the incidence of the excitation light. Through such an out‐of‐plane orientation of azo chromophores, parallel to the [111] fcc crystallographic axis, the effective refractive index of the photonic crystal medium was decreased. Therefore, a blue‐shift in bandgap positions was consequently induced with 20–40 nm tuning ranges. The out‐of‐plane orientation was confirmed by angular resolved absorption spectral measurements. 相似文献
8.
利用时域有限差分法和实验结果对胶体晶体结构和传输特性进行了研究.构成三维胶体晶体的小球直径和折射率对禁带的位置会产生影响,用时域有限差分法对不同参数的胶体晶体进行了数值计算.计算结果和实验数据表明三维胶体晶体在纵向存在带隙,而且可以得到透反射谱和不同位置的场分布. 相似文献
9.
When fresh tetraethylorthosilicate is introduced into a colloidal suspension of silica spheres, it hydrolyzes and condenses in situ to arrest and fix the dimers resulting from constant collisions between the spheres. By optimizing the experimental parameters (including the length of aging time) and the diameter of the silica spheres, as well as the concentrations of counterions, water, and ammonia, it is possible to routinely produce monodisperse dimers with a yield as high as 50 %. When combined with centrifugation using a density gradient medium, the yield of such dimers could be further increased to 80 %. It is believed that this method will provide a simple and versatile approach to the high‐volume production of dimers from spherical colloids composed of different materials. These dimers may find widespread use in a range of applications such as fabrication of photonic crystals and fundamental studies related to colloidal science. 相似文献
10.
In colloidal suspensions of silica, particles undergo constant collisions. By controlling various parameters, the repulsive barrier can be reduced, thereby substantially increasing the number of collision‐induced dimerization events. Xia and co‐workers report on p. 1627 that the dimers could be arrested and then permanently fixed by introducing a small amount of fresh tetraethylorthosilicate into the colloidal suspension, with monodisperse dimer yields of up to 50 %. This yield could be increased to 80 % by centrifugation in a density gradient medium. When fresh tetraethylorthosilicate is introduced into a colloidal suspension of silica spheres, it hydrolyzes and condenses in situ to arrest and fix the dimers resulting from constant collisions between the spheres. By optimizing the experimental parameters (including the length of aging time) and the diameter of the silica spheres, as well as the concentrations of counterions, water, and ammonia, it is possible to routinely produce monodisperse dimers with a yield as high as 50 %. When combined with centrifugation using a density gradient medium, the yield of such dimers could be further increased to 80 %. It is believed that this method will provide a simple and versatile approach to the high‐volume production of dimers from spherical colloids composed of different materials. These dimers may find widespread use in a range of applications such as fabrication of photonic crystals and fundamental studies related to colloidal science. 相似文献
11.
S. Kim B. Yang S. Hou J. Lee F. Papadimitrakopoulos 《Advanced functional materials》2006,16(12):1590-1598
DNA supramolecular recognition is employed for the immobilization of 2D photonic crystals of monodisperse colloidal microspheres. Amine‐terminated DNA oligomers are covalently attached to carboxy‐decorated microspheres and substrates while preserving their colloidal stability and organization properties. Following a capillary‐force‐assisted organization of DNA‐decorated microspheres into close‐packed 2D opaline arrays, the first monolayer is immobilized by DNA hybridization. Various parameters affecting the long‐range order of such opaline arrays are investigated, including surface hydrophobicity and the relative strengths of the specific versus nonspecific interactions. The type and concentration of salt and the process temperature are also optimized for the hybridization between microspheres and substrate. The selective removal of non‐specifically bound multilayers is accomplished by carefully passing an air/liquid interface over these arrays. DNA hybridization was found to play an important role in immobilizing the first monolayer of 2D opaline arrays while preserving its long‐range order, with an approximate binding strength three times higher than that of non‐specific interactions. 相似文献
12.
Timothy L. Kelly Yuri Yamada Celine Schneider Kazuhisa Yano Michael O. Wolf 《Advanced functional materials》2009,19(23):3737-3745
A new poly(p‐phenylenevinylene) (PPV) composite material has been developed by the incorporation of insoluble PPV polymer chains in the pores of monodisperse mesoporous silica spheres through an ion‐exchange and in situ polymerization method. The polymer distribution within the resultant colloidal particles is characterized by electron microscopy, energy dispersive X‐ray microanalysis, powder X‐ray diffraction, and nitrogen adsorption. It was found that the polymer was selectively incorporated into the mesopores of the silica host and was well distributed throughout the body of the particles. This confinement of the polymer influences the optical properties of the composite; these were examined by UV–vis and fluorescence spectroscopy and time‐correlated single‐photon counting. The results show a material that exhibits an extremely high fluorescence quantum yield (approaching 85%), and an improved resistance to oxidative photobleaching compared to PPV. These enhanced optical properties are further complemented by the overall processability of the colloidal material. In marked contrast to the insolubility of PPV, the material can be processed as a stable colloidal dispersion, and the individual composite spheres can be self‐assembled into opaline films using the vertical deposition method. The bandgap of the opal can be engineered to overlap with the emission band of the polymer, which has significant ramifications for lasing. 相似文献
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14.
Yin Hai-Rong Gong Yu-Bin Wei Yan-Yu 《Journal of Infrared, Millimeter and Terahertz Waves》2009,30(9):982-993
In this paper, relations between photonic band gaps and operating mode of slow-wave circuits constructed by photonic crystals
are discussed, and methods for computing photonic band gaps and determining the operating band are given. As an example, a
slow-wave circuit containing two-dimensional photonic crystals is analyzed. The results explain that complete photonic band
gap is not necessary for traveling wave tubes, and more than one defect-mode maybe coexists inside one photonic band gap.
If there have no complete photonic band gap, special input and output circuits capable of customizing modes are necessary.
Compared with conventional traveling wave tubes, the numerical results do not suggest the bandwidth of the photonic crystal
traveling wave tube is wider, and the interaction impedance is lower.
This work was supported in part by the National Natural Science Foundation of China under Grant 60532010 and 60401005. The
authors are with University of Electronic Technology and Science of China, Chengdu, China, 610054. 相似文献
15.
This paper surveys recent developments in engineering physics approaches and self‐assembly chemistry methodologies for creating 3D photonic crystals and how this has led to in‐wafer patterned colloidal crystals. These materials are comprised of single crystal micrometer scale features of silica colloidal crystals that have controlled thickness, area, and orientation and are embedded within a single crystal silicon wafer. Two processes for growing opal‐patterned chips are described. One is based upon microfluidic and the other spin coating driven self‐assembly of colloidal silica micro‐spheres within a lithographic patterned silicon wafer. 相似文献
16.
I. Soten H. Miguez S.M. Yang S. Petrov N. Coombs N. Tetreault N. Matsuura H.E. Ruda G.A. Ozin 《Advanced functional materials》2002,12(1):71-77
Barium titanate inverted opals with powder and film morphologies were synthesized from barium ethoxide and titanium isopropoxide in the interstitial spaces of a polystyrene opal. This procedure involves infiltration of precursors into the interstices of the polystyrene opal template followed by hydrolytic polycondensation of the precursors to amorphous barium titanate and removal of the polystyrene opal by solvent extraction or calcination. In‐situ variable temperature powder X‐ray diffraction and micro‐Raman spectroscopy allow one to observe the thermally induced transformation of the as‐synthesized amorphous barium titanate inverted opal to the nanocrystalline form. In this way, a nanocrystalline barium titanate inverted opal can be engineered as either the cubic or tetragonal polymorph. Control of this process is key to the practical realization of a room‐temperature stable ferroelectric barium titanate inverted opal that can be thermally tuned through the ferroelectric–paraelectric transition around the Curie temperature. Optical characterization demonstrated photonic crystal behavior of the inverted barium titanate opals and results were in good agreement with photonic band structure calculations. The synthesis of optical quality ferroelectric barium titanate inverted opals provides an opportunity to electrically and optically engineer the photonic band structure and the possibility of developing tunable three‐dimensional photonic crystal devices. 相似文献
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18.
Boyang Ding Maria Bardosova Ian Povey Martyn E. Pemble Sergei G. Romanov 《Advanced functional materials》2010,20(5):853-860
Photonic heterocrystals are prepared by sandwiching films of self‐assembled opal and force‐assembled Langmuir–Blodgett colloidal crystals. Anomalously strong light scattering in conjunction with low reflectivity is observed with increasing angle of incidence in the spectral range of photonic bandgaps. The occurrence of light scattering at the interface has been assigned to the optical mode mismatch between the two types of photonic crystals. Photonic bandgap‐related mechanisms of trapping the decaying photonic crystal modes at the interface are suggested. 相似文献
19.
复周期结构光子晶体的光子能带特性研究 总被引:4,自引:5,他引:4
本文构思了一种每个周期内部有几个不同的小单元的复周期结构光子晶体,并利用光学传输矩阵法对这种光子晶体进行了数值模拟计算。计算结果表明,这种复周期结构光子晶体比普通结构的光子晶体多出1个大的光子禁带区。适当调整参数还可以分别获得多通道窄带滤波特性、带通滤液特性和窄带透过特性。 相似文献