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We measured and calculated transmission spectra of two-dimensional quasiperiodic photonic crystals (PCs) based on a 5-fold (Penrose) or 8-fold (octagonal) symmetric quasiperiodic pattern. The photonic crystal consisted of dielectric cylindrical rods in air placed normal to the basal plane on vertices of tiles composing the quasiperiodic pattern. An isotropic photonic band gap (PBG) appeared in the TM mode, where electric fields were parallel to the rods, even when the real part of a dielectric constant of the rod was as small as 2.4. An isotropic PBG-like dip was seen in tiny Penrose and octagonal PCs with only 6 and 9 rods, respectively. These results indicate that local multiple light scattering within the tiny PC plays an important role in the PBG formation. Besides the isotropic PBG, we found dips depending on the incident angle of the light. This is the first report of anisotropic structures clearly observed in transmission spectra of quasiperiodic PCs. Based on rod-number and rod-arrangement dependence, it is thought that the shapes and positions of the anisotropic dips are determined by global multiple light scattering covering the whole system. In contrast to the isotropic PBG due to local light scattering, we could not find any PBGs due to global light scattering even though we studied transmission spectra of a huge Penrose PC with 466 rods.

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A needle-like probe is the simplest tool to manipulate fine spheres. It catches fine spheres by adhesion forces without any holding device. Metallic spheres of 10-100 mm are difficult to manipulate with the needle-like probe, because the gravity rivals the adhesion forces in the dynamics of the spheres. Large and heavy spheres arranged on a substrate are easily disturbed because of the same reason. Here, a manipulator equipped with a direct power source, which applies voltage to the probe, is fabricated. Large and heavy spheres are adhered by the controllable electrostatic force. Besides the manipulation, the apparatus is designed to weld the spheres by using the probe as electrode for spot/arc welding. Experiments on the manipulation showed that the probe caught gold spheres of 40-80 mm by applying 20-50 V and released by putting them down after cutting the power off. Following to manipulation, welding experiments were carried out at various conditions. Two power sources, a high-voltage and low-current power source and a low-voltage and high-current power source, and two welding methods, arc welding and spot welding, are examined. The experiments showed that the gold spheres of 40-80 mm can be welded by the spot welding using the high-voltage and low-current power source, of which maximum power rating is 10 kV!1 mA. The probe is kept to touch the sphere and 4 kV or more is applied. Electric sparks are generated at the interface of the probe and the substrate, and the sphere is welded to the substrate. In both the manipulation and welding, the contact pressure must be very low. A tower of gold spheres is fabricated as an example of three-dimensional microstructures composed of fine spheres. q

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