Diffraction in crystalline colloidal-array photonic crystals
Diffraction in crystalline colloidal-array photonic crystals
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DOI：
10.1103/physreve.69.066619
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发表时间：
2004-06-01
影响因子：
2.4
通讯作者：
Kesavamoorthy, R
中科院分区：
文献类型：
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作者：
Asher, SA;Weissman, JM;Kesavamoorthy, R
我们研究了由直径为270 nm的聚苯乙烯微球组成的晶体胶体阵列（CCA）光子晶体的衍射和晶体结构。这种CCA在大约1200 nm处衍射一阶光，并且在可见光谱区域中显示出来自高阶平面的强衍射。我们定量地检测了推定的fcc（111）、（200）、（220）和（311）面的相对衍射强度。将这些强度与理论计算的强度进行比较，我们发现晶体结构为面心立方，具有明显的层错。基本上，对于fcc（111）平面，即使通过类似于40 μ m厚的薄CCA，也没有光以布拉格角透射。然而，由于晶体缺陷，大部分光在布拉格角附近漫散射。对于fcc（200）、（220）和（311）面，在布拉格条件下取向的薄样品发生显著的透射。我们还观察到适度强烈的二维衍射从晶体表面的前几层。我们还研究了由类似于120 nm的聚苯乙烯球制备的CCA光子晶体的衍射随样品厚度的变化，其fcc（111）面在可见光谱区相互作用。这些实验观察，辅助计算的基础上一个简单但灵活的模型，从任意收集的胶体球的光散射，清楚地表明，制造三维光子带隙晶体将受到挑战的晶体缺陷。
We characterized the diffraction and crystal structure of a crystalline colloidal array (CCA) photonic crystal composed of 270 nm diameter polystyrene spheres which have a nearest neighbor spacing of similar to540 nm. This CCA diffracts light in first order at approximate to1200 nm and shows strong diffraction in the visible spectral region from higher order planes. We quantitatively examined the relative diffraction intensities of the putative fcc (111), (200), (220), and (311) planes. Comparing these intensities to those calculated theoretically we find that the crystal structure is fcc with significant stacking faults. Essentially, no light transmits at the Bragg angle for the fcc (111) planes even through thin similar to40 mum thick CCA. However, much of this light is diffusely scattered about the Bragg angle due to crystal imperfections. Significant transmission occurs from thin samples oriented at the Bragg condition for the fcc (200), (220), and (311) planes. We also observe moderately intense two-dimensional diffraction from the first few layers at the crystal surfaces. We also examined the sample thickness dependence of diffraction from CCA photonic crystals prepared from similar to120 nm polystyrene spheres whose fcc (111) planes diffract in the visible spectral region. These experimental observations, aided by calculations based upon a simple but flexible model of light scattering from an arbitrary collection of colloidal spheres, make clear that fabrication of three-dimensional photonic band gap crystals will be challenged by crystal imperfections.