Elucidation of the behavior of photons in photonic crystals mechanically assembled from sub-micron particles

研究了微米级介质球组成的声子晶体中的光子行为。本研究的重点是基于机械操纵的制备方法、光子从晶体中散射的衍射实验观察和基于矢量谐波展开的理论分析；通过改进真空系统，建立了亚微米粒子的操纵技术；发展了选区衍射显微镜技术来检测所制备的光子晶体对光的衍射。通过改变晶体的晶格结构、入射光的方向和波长，系统地观察到了光子晶体的散射波。结果发现，在一定入射条件下，出现了反常的布拉格衍射。衍射效率的波长依赖关系与Mie散射特性非常相似。此外，还发展了一种有限球阵列的计算方法。由于球体内部电场的计算已经成为可能，光子的行为可以清楚地可视化。计算结果与实验观测结果吻合较好。阐明了光子晶体的反常布拉格衍射起源于仅由几个球体组成的单元阵的特性。光子晶体的布拉格衍射只有在光从球体传输到球体的过程中偶然地被矢量谐振模的位相匹配激活时才会产生。此外，在计算结果中还观察到来自光子晶体的光子的相干后向散射。

The behavior of photons in phonic crystals composed of micrometer-sized dielectric spheres has been investigated. The points of this research are the fabrication method based on mechanical manipulation, the experimental observation of diffraction of photons scattered from the crystals, and the theoretical analyses based on vector harmonics expansion.By improving the vacuum system, manipulation technique of sub-micron particles has been established.A selected area diffraction microscopy technique has been developed to examine the diffraction of light by the fabricated photonic crystals. By varying the lattice structure of crystals, incident direction of the light, and the wavelength, the scattered waves from the photonic crystals have been systematically observed. As a result, anomalous Bragg diffraction has been discovered for a certain incidence condition. The wavelength-dependence of the diffraction efficiency was very similar to that of the Mie scattering characteristics.Furthermore, a calculation technique of finite arrays of spheres has been newly developed. Since the calculation of the electric fields inside the spheres has become possible, the behavior of photons can be clearly visualized. All the experimentally observed results were reproduced by the calculation. It has been clarified that the anomalous Bragg diffraction of photonic crystals originates from the characteristics of a unit array composed of only a few spheres. The Bragg diffraction of a photonic crystal arises only when the light propagation from spheres to spheres is accidentally enabled by the phase matching of vector harmonics mode. Moreover, a coherent backscatteing of photons from a photonic crystal has been observed in the calculation results.